Computer Analysis of an Archaeological Landscape: Medieval Land Divisions in the Isle of Man 9780860545460, 9781407318103

Table of contents :
Cover Page
Copyright Page
Table of Contents
List of Illustrations
Acknowledgements
Preface
Chapter 1: The Roots of the Manx Land System
Chapter 2: Making the Data Available
Chapter 3: Tools for Data Analysis
Chapter 4: Early Pagan Vikings on Man
Chapter 5: Pagan Viking Settlements?
Chapter 6: Early Medieval Proto Parishes?
Chapter 7: Burials on Boundaries?
Chapter 8: An Improverished Database?
Chapter 9: Conclusions
Appendix
Bibliography
Abbreviations
Works Cited

Citation preview

Computer Analysis of an Archaeological Landscape Medieval Lan4.. . . Divisions in the Isle of Man

Paul Reilly

BAR British Series 190 1988

B.A.R.

122 Banbury Rd, Oxford, OX2 7BP, UK

GENERAL EDITORS A.R. Hands, B.Sc., M.A., D.Phil. D.R. Walker, M.A.

BAR 190,1988 'Computar Analysis of an Archaeological Landscape'.

@ Paul Reilly The author’s moral rights under the 1988 UK Copyright, Designs and Patents Act are hereby expressly asserted.

All rights reserved. No part of this work may be copied, reproduced, stored, sold, distributed, scanned, saved in any form of digital format or transmitted in any form digitally, without the written permission of the Publisher. ISBN 9780860545460 paperback ISBN 9781407318103 e-book DOI https://doi.org/10.30861/9780860545460 A catalogue record for this book is available from the British Library This book is available at www.barpublishing.com

T ab le o f C on ten t s C hap te r 1 :T he R oo ts o ft h e Manx L and S ys tem T he I s land ' s K ey P o s i t ion i nt h e I r i sh S ea I s land G eog raphy T he Manx L and S y s tem Qua r te r land s T r een s P a r i she s S head ing s T he D eem s te r D iv i s ion s I n tack s C ommon land O the r Sma l l L and Un i t s I n su la r D a t ing E v idence f o rt h e Ia nd S y s tem Q ua r te r land s T r een s P a r ishe s S head ing s T he D eems te r D iv i s ion s E x ter na l E v idence R e levan t t ot h e L and S y s tem P l ac ing t h e Q ua r te r land s a nd T r eens i n aW ide r C on tex t P lac ing t he P a r i she s i n aW ide r C on tex t T he B a s i s o ft h e Manx P a roch ia l S t ruc tu re : aT en ta t ive Mode l P la c ing t h e S head ing s a nd D eem s te r D iv i s ion s i n aW ide r C on tex t L and a nd S oc ia l D if f e r en t ia t ion T he Ma in S tumb l ing B lock : h ow c an w e o ve r come i t ?

1 1 6 8 1 1 2 1 2 1 5 1 6 1 7 1 8 1 8 1 9 1 9 2 0 2 0 2 2 2 2 2 2 2 4 2 8 3 5 3 8 4 1 4 3

C hap te r 2 : Mak ing t h eD a ta A va i lab le T he BOUNDER S y s tem D e s ign ing t he S y s tem S torage I naccurac ie s D a ta -En t ry P roce s s ing T ime s F i le O rgan i sa t ion B lock ing o fR eco rd s D e sc r ip t ion o ft h e F i le s S pec i f y ing H ighe r L eve l Un i t s S TAGE 1-R econ s truc t ing t h e B ounda r ie s o fA l l t h e C omponen t U n i t s S TAGE 2-E l im ina t ion o ft h e I n te rna l B ounda r ie s S TAGE 3-D e te rm ina t ion o f aC on t inuou s B ounda ry f o rt h e N ew Un i t R eco rd ing a nd S tor ing aT heo r e t ica l L and -Sy s tem D ig i t i s ing t he B ounda r ie s T he H a rdwa r e T he C onve r s ion P rog ram Me rg ing A d jacen t Map s An A s se s smen t o ft h e BOUNDER S y s tem

4 5 4 6 4 6 4 6 4 7 4 7 4 7 4 7 5 0 5 1 5 3 5 5 6 5 7 5 8 6 0 6 1 6 1 6 2 6 3

C hap te r 3 :T oo ls f o r Da ta A na lys is E x tend ing t h e S y s tem : BOUNDER ! ! A s s ign ing aS i te -Loca t ion t oi t s P a r en t U n i t C a lcu la t ing t h e A r ea o f aS pec if ied Ia nd U n i t Mea su r ing S i te -Loca t ion t o B ounda ry D i s tance s Mea sur ing t h e L eng th o f aB ounda ry P lo t t ing o u t aB ounda ry O the r P os s ib le Mea suremen t s

6 4 6 5 6 5 7 2 7 4 7 5 7 6 7 6

T ab le o fC on ten ts

i

P rog ram I mp lemen ta t ion V a l ida t ing t h e BOUNDER a nd BOUNDER ! ! S y s tem s An A s se s smen t o ft h e BOUNDER ! ! S y s tem

7 7 8 7 8

C hap te r 4 :E a r ly P agan V ik ing s o n Man T he P rob lem o fC e l t ic S urv iva l D ocumen ta ry E v idence L anguag e P l a ce -Name s R un ic I n sc r ip t ion s Memor ia l S cu lp tu r e T he B u r ia l R ecord Hoa rd s O ccupa t ion S i te s P hy s ica l An th ropo logy a nd B io log ica l T ra i t Ana ly s is I s a' No r se -Co lony ' o n Man aV a l id C oncep t? C e l t ic S urv iva l?

8 0 8 0 8 2 8 3 8 3 8 5 8 9 9 1 1 00 1 0 1 1 08 1 08 1 09

C hap te r 5 :P agan V ik ing S e t t lemen t s ? V ik ing F a rm s tead s i nJ u rby ? T he I l i te ra te Man ' s L and C ha r te r ? T he G rave - Mound s i nJ u rby E x t rac t ing t h e B ounda ry D a ta f r om t h e B a se Map s C ompe t ing Mode l s H ypo the s i s 1 Mode l l ing t h e D is t r ibu t ion o fG rave - Mound s i nJ u rby H ypo the s i s 2 H ypo the s i s 3 D i scu s s ion

11 13 14 16 1 20 1 20 1 2 1 1 2 1 1 25 1 27 1 29

C hap te r 6 :E a r ly Med ieva l P ro to P a r ishe s " K ee i l l s a nd Rhu l l ick s P rev iou s Wo rk o nt h e K ee i l l s a nd Rhu l l ick s T he K ee il -T reen H ypo the s i s P rob lem s Wi th T he D a t ing O fT he K ee i l l s And R hu l l icks O the r P rob lem s Mode l l ing t h e K ee il -T r een D i s t r ibu t ion s T he S i te s T he L and Un i t s T he S imu la t ion s C ompu te r I mp lemen ta t ion S imu la t ing S i te s o ve rt h e S econda ry L eve l Un i t s o fS amp le A rea 1 S imu la t ing S i te s o ve rt h e S econda ry L eve l Un i t s o fS amp le A r ea 2 S imu la t ing S i te s o ve rt h e P r ima ry L eve l Un i t s o fS amp le A rea 1 S imu la t ing S i te s o ve rt h e P r ima ry L eve l U n i t s o fS amp le A r ea 2 D i scu s s ion

1 32 1 32 1 33 1 36 1 39 1 4 1 1 43 1 43 1 43 1 44 1 44 1 49 1 49 1 50 1 50 1 55

C hap te r7 :B u r ia ls o n B ounda r ie s ' K ee i l l s , Rhu l l ick s a nd B ounda ry A s soc ia t ion s B ounda r ie s : No Man ' s L and o rA c t iv i ty A rea s? C hape l s , B u r ia l s , B ounda ry Ma rk ing a nd B ounda ry Ma in tenance Quan t i f y ing B ounda ry A s soc ia t ion s P rob lem s w i th t h e D a ta App ly ing t h e Annu lu s Me thod t ot h e Manx D a ta AC r i t ique o ft h e Annu lu s Me thodo logy w i th R e f e r ence t ot h e Manx D a ta A Mon te C a r lo App roach t ot h e P rob lem D i s cu s s ion

1 56 1 57 1 59 1 66 1 68 1 72 1 74 1 75 1 80 1 84

C hap te r 8 :A n I mpo ve r ished D a tabase ? P rob lem A rea s C eme te r ie s a nd t h e i r C u l tu ra l L and scape C eme te ry Manag emen t T he N eed f o r A l te rna t ive A pp roache s AC a se S tudy : aK ee i l l S urvey a tS ca r le t t P oi n t N ew I nve s t iga t ion s a t Ma lew 1 8 T opog raph ic S urvey T he Wi re -F ramed S ur f ace

1 87 1 88 1 89 1 89 1 90 1 94 1 94 1 9 7 1 98

T ab le o fC on ten ts

i i

D a ta E nhancemen t S p l in ing a nd P seudo I l lum ina t ion Z -C l ipp ing R e s i s t iv i ty S u rv ey W i r e -F ramed Mode l o ft h e R e s i s t iv i ty S urvey D a ta U s ing t h e I AX I mag e P roce s s ing S y s tem t o E xam ine t h e R e s i s t iv i ty D a ta AF o rgo t ten K ee i l l E xcava t ion a tS ca r le t t I d en t i fy ing t h e S i te T he S i gn if i cance O fT he A na ly se s

1 9 9 2 0 1 2 02 2 05 2 05 2 07 2 08 2 11 2 12

C hap te r 9 :C onc lus ions N ew L igh t o n t h e Manx A r chaeo log ica l L and scape : AR e sume O the r Appl i ca t ion A r ea s R ecommenda t ion s

2 17 2 19 2 2 1 2 2 1

A ppend ix E s t ima t ing T he T heo r e t ica l P robab i l i t ie s a nd t h e ir A s soc ia ted C onf idence L im i t s f r om t h e S imu la t ion s

2 23

B ib l iog raphy Abb r ev ia t ion s Wo rk s C i ted

2 26 2 26 2 27

Tab le o fC on ten ts

2 23

i v

L i s t o fI lu s t ra t ion s F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re

1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 . 9 . 1 0 . 1 . 1 2 . 1 3 . 1 4 . 1 5 . 1 6 . 1 7 .

F igu re 1 8 . F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re F igu re

1 9 . 2 0 . 2 1 . 2 2 . 2 3 . 2 4 . 2 5 . 2 6 . 2 7 . 2 8 . 2 9 . 3 0 . 3 1 . 3 2 . 3 . 3 4 . 3 5 . 3 6 . 3 7 . 3 8 . 3 9 . 4 0 . 4 1 . 4 2 . 4 3 . 4 4 . 4 5 . 4 6 . 4 7 . 4 8 . 4 9 .

T he L oca t ion o ft he I s le o f Man w i th in t he I r i sh S ea 5 P r inc ipa l l a nd d i v i s ion s o ft he I s le o f Man 9 L and d i v i s ion s i nt he p a r i sh o fA rbo ry 1 0 T he S t ruc tu re o ft he L and S y s tem o n t h e I s le o f Man 1 P a r i sh c hu rche s a nd p a r i she s o ft he I s le o f Man 1 3 P a r i sh c ompo s i t ion i nt he s head ing o fG lenf aba 1 4 P a r i sh c ompo s i t ion i nt he s head ing o fM ichae l 1 4 P a r i sh c ompo s i t ion i nt he s head ing o fA y re 1 4 P a r i sh c ompo s i t ion i nt he s head ing o fG a rf f 1 5 P a r i sh c ompo s i t ion i nt he s head ing o fM idd le 1 5 P a r i sh c ompo s i t ion i nt he s head ing o fR u shen 1 5 S head ing s i nt h e No r th s ide o ft he I s le o f Man 1 6 T he a r ea s o ft h e p a r i she s a nd s head ing s o ft he I s le o f Man 1 7 S head ing s i nt he S ou th s ide o ft he I s le o f Man 1 6 P r ima ry d i v i s ion s 1 7 S head ing d i s t r ic t s o ft he I s le o f Man 2 3 L oca t ion o fp a r i sh c hu rche s o n p a ren t t r een u n i t s i nA rbo ry , B a l laugh , J u rby a nd B raddan 3 2 L oca t ion o fp a r i sh c hu rche s o n p a ren t t r een u n i t s i n And rea s , Onchan a nd M ichae l 3 L oca t ion o fp a r i sh c hu rche s o n p a ren t t r een u n i t s i nB r ide a nd R u shen 3 4 L oca t ion o fp a r i sh c hu rche s o n p a ren t t r een u n i t s i nP a t r ick a nd G e rman 3 5 L oca t ion o fp a r i sh c hu rche s o n p a ren t t r een u n i t s i nL onan a nd S an ton 3 6 K ey t o F igu re 1 7 o n p age 3 2 t o F igu re 2 1 o n p age 3 6 i n c lu s ive 3 7 T he mu l t ip le E s ta te Mode l ( s ou rce : J one s , 1 979 ) 4 2 F i le o rgan i sa t ion 4 8 Q ua r te r land s i nt he t r een o f Knok sewe l l , Ruby 5 4 T heo re t ica l L and S y s tem 5 9 I n te rmed ia te D a ta F i le 6 0 Me rg ing a d jacen t m ap s 6 2 T e s t f o r d ec id ing w he the r o r n o t ap o in t l i e s i n s ide au n i t 6 6 T he t e s t a pp l ied t o c omp lex p o lygon s 6 6 M i s lead ing c a se s 6 7 R ay c a s t ing u s ing ad i g i t i sed b oundary 6 8 T e s t ing f o r b ounda ry i n te r sec t ion s 6 9 D e te rm in ing t h e d i rec t ion o f ar ay 7 0 C a lcu la t ing t he a r ea e nc lo sed b y ad i g i t i sed b ounda ry 7 3 D e te rm in ing t he l onge s t a nd s ho r te s t s i te loca t ion t o b oundary d i s tance s 7 5 C e l t ic c ro s se s h e ld i nt he p a r i sh c hur ch o f Maugho ld 9 0 S cand inav ian c ros se s i nt he p a r i sh c hu rch o fB raddan 9 1 V iew o ft he C ronk n y Me r r ieu p romon to ry f o r t a nd b each 1 06 A e r ia l v i ew o ft he C ronk n y Me r r ieu p romon tory f o r t a nd b each •••• 1 07 V iew o ft he C a s s n y H aw in p romon tory f o r t a nd b each 1 07 P agan V ik ing g rave -mound a t K nock y Doonee , And rea s 12 Two p agan V ik ing g rave -mound s i nJ u rby 12 D i s t r ibu t ion m ap s how ing t he l o ca t ion s o fg rave -mound s i nJ u rby .. 16 D i s t r ibu t ion m ap s how ing t he p r imary u n i t s o fJ u rby 17 G rave -mound s a nd p r ima ry u n i t s i nt he P a r i sh o fJ u rby 18 G ene ra t ing ar andom c o -o rd ina te w i th in a s pec i f ied a r ea 1 22 F low -cha r t r e p re sen t ing t he s imu la t ion p rocedu re f o l lowed 1 23 B a r c ha r t s how ing t he e s t ima ted p robab i l i ty o fu n i t s h av ing mo re t han

L is t o fI lus t ra t ions

o ne mound F igu re 5 0 . C umu la t ive f r equency c u rve o fu n i t s w i th mo re t han o ne mound ... F igu re 5 1 . B a r C ha r t s how ing t he e s t ima ted p robab i l i ty o fc oa s ta l u n i t s h av ing mound s F igu re 5 2 . C umu la t ive f r equency c u rve o fc oa s ta l u n i t s h av ing mound s F igu re 5 3 . G rave -mound s o n t he c oa s ta l r i dge o fJ u rby F igu re 5 4 . I n te r s i te d i s tance s b e tw een n e ighbou r ing c oa s ta l g rave -mound s F igu re 5 5 . C umu la t ive p robab i l i ty d i s t r ibu t ion s f o r K o lmogo rov -Sm i rnov t e s t .. F igu re 5 6 . K o lmogo rov -Sm i rnov T e s t f o r H ypo the s i s 3 F igu re 5 7 . T he r ema in s o f ak ee i l l a t R ona ld sway F igu re 5 8 . T he r ema in s o f ak ee i l l a tS u lb r ick F igu re 5 9 . T he r ema in s o fS a in t P a t r ick ' s c hape l a nd b u r ia l g round i nJ u rby ... F igu re 6 0 . I mp rov ing s e a rch t ime s b y r educ ing t h e s i ze o ft he s amp l ing f r ame .. F igu re 6 1 . Map s how ing t he l o ca t ion o fS amp le A rea 1& S amp le A rea 2 F igu r e 6 2 . S chema t ic d i ag ram s how ing t he s t age s o ft h e s i te to -un i t s imu la t ion . F igu re 6 3 . T he d i s t r ibu t ion s o fk ee i l l / rhu l l ick s i te s o ve r s e conda ry l e ve l u n i t s .. F igu re 6 4 . E s t ima ted p robab i l i ty d i s t r ibu t ion o fs i te s i ns e condary u n i t s i nS amp le A rea 1 F igu re 6 5 . E s t ima ted c umu la t ive p robab i l i ty d i s t r ibu t ion o fs i te s i ns e condary u n i t s i nS amp le A rea 1 F igu re 6 6 . E s t ima ted p robab i l i ty d i s t r ibu t ion o fs i te s i ns e condary u n i t s i nS amp le A rea 2 F igu re 6 7 . E s t ima ted c umu la t ive p robab i l i ty d i s t r ibu t ion o fs i te s i ns e conda ry u n i t s i nS amp le A rea 2 F igu re 6 8 . E s t ima ted p robab i l i ty d i s t r ibu t ion o fs i te s i np r imary u n i t s i nS amp le A rea 1 F igu re 6 9 . E s t ima ted c umu la t ive p robab i l i ty d i s t r ibu t ion o fs i te s i np r ima ry u n i t s i nS amp le A rea 1 F igu re 7 0 . E s t ima ted p robab i l i ty d i s t r ibu t ion o fs i te s i np r imary u n i t s i nS amp le A rea 2 F igu r e 7 1 . E s t ima ted c umu la t ive p robab i l i ty d i s t r ibu t ion o fs i te s i np r ima ry u n i t s i nS amp le A rea 2 F igu re 7 2 . K ee i l l -rhu l l ick s i te s a nd t r een s i nt he s head ing o fR u shen F igu re 7 3 . K ee i l l rhu l l ick s i te s a nd q ua r te r land s i nt h e p a r i sh o fM ichae l F igu re 7 4 . T he r ema in s o ft he L ag -ny -Kee i l ley b u r ia l g round , k ee i l l a nd p r ie s t ' s c e l l F igu re 7 5 . T he l o ca t ion o fL ag -ny -Kee i l ley F igu re 7 6 . T he r ema in s o ft he C ronk -y -Kee i l lee b u r ia l g round a nd k ee i l l F igu re 7 7 . T he l o ca t ion o fK ee i l l V ae l a nd C ronk -y -Kee i l lee F igu r e 7 8 . B e r su type r ound h ou se s i te s o n t h e b ounda ry o f Ma lew a nd A rbory F igu re 7 9 . B e r su r ound h ou se s i te s a tB a l lake igan o n t h e b oundary ( s t ream ) o f Ma lew a nd A rbory F igu re 8 0 . C oncen t r ic b oundary z one s o fe qua l w id th h u t d i ff e ren t a r ea s F igu re 8 1 . T he b ounda ry a nnu lu s m e thod F igu r e 8 2 . T ab le s how ing t he d i s t r ibu t ion o fs i te s o ve r p r imary ( 1Y ) a nd s e conda ry ( 2Y ) l e ve l u n i t s i ne ach p a r i sh F igu re 8 3 . T ab le g i v ing t h e n umbe r o fp r imary ( 1Y ) a nd s e condary ( 2Y ) l e ve l u n i t s a nd t he t o ta l a r ea o fe ach p a r i sh F igu re 8 4 . S u mmary o ft he r e su l t s o fa pp ly ing Good ie r ' s p ub l i shed t e s t F igu re 8 5 . Mode l l a nd s y s tem s how ing b oundary a nnu l i F igu re 8 6 . S ummary o ft he r e su l t s o fa pp ly ing t he mod i f ied t e s t F igu re 8 7 . Mea su r ing t he l e ng th o ft he e dge o f al e af F igu re 8 . S chema t ic r ep re sen ta t ion o ft he b ounda ry t o s i te loca t ion s imu la t ion p roce s s F igu re 8 9 . D i s t r ibu t ion o fs i te s w i th in S amp le A rea 1b ounda ry a nnu l i F igu re 9 0 . D i s t r ibu t ion o fs i te s w i th in S amp le A r ea 2b oundary a nnu l i F igu re 9 1 . M in imum s i te loca t ion t o s e conda ry u n i t b ounda ry d i s tance s i nS amp le A rea 2(Ma rown & S an ton ) F igu re 9 2 . M in imum s i te loca t ion t o p r imary u n i t b ounda ry d i s tance s i nS amp le A rea 2(Ma rown & S an ton ) F igu re 9 3 . T ab led c r i t ica l v a lue s o fDw i th 1 8 d eg ree s o ff r eedom ( s ou rce : E bdon , 1 979 ) F igu re 9 4 . L oca t ion Map : Ma lew 1 8 L is t o fI lus t ra t ions

1 24 1 24 1 26 1 26 1 27 1 28 1 30 1 30 1 34 1 35 1 35 1 45 1 47 1 48 1 50 1 5 1 1 5 1 1 52 1 52 1 53 1 53 1 54 1 54 1 56 1 57 1 59 1 60 1 6 1 1 62 1 65 1 66 1 7 1 1 72 1 75 1 75 1 76 1 77 1 78 1 79 1 8 1 1 82 1 83 1 85 1 85 1 86 1 95 v i

"/K-;S

e n t r ie s ( i . e . NEB ) s t ar t ing a t 1 =5 ( i . e . FEB ) .

T he se i nd ica te 3

( PO INTS ) e n t r ie s ( i . e . NEP )t ob ec oun ted b ackwards ( hence t h e ' ' ) f r om t he e n t ry a t1 =4 ( i . e . FEP ) , f o l lowed b y t he 2c onsecu t ive e n t r ie s f r om 1 = 1 0 . T h is u n i t a l so h a s 6( S ITES } e n t r ie s ( i . e . NES ) b eg inn ing a t I = 2( i . e . FES ) ; t h e LNK v a lue s s how t ha t t he se 6 s i te s a re a t 1 = -2 ,N , 9 ,6 ,& 7 .T h i s e xamp le a l so s how s t ha t t h e ( AD M IN ) u n i ta t1 = 9i sc ompo sed o f 3s ub -un it s ( i . e . NES ) w ho se n umbe r s ( 7 , 5 ,& 3 )a re l i s ted c onsecu t ive ly f r om e n t ry I= 2 ( i . e . FES ) .

F igu re 2 4 i l u s t ra te s t h e f i l e s a nd s u mmar i se s t he r e la t ionsh ip s b e tween t hem . I ts how s s chema t ica l ly h ow a t r ee l ike s t ruc tu re o fp o in te r s , e mana t ing f r om t h e f i l e { AD MI N } c an b e u sed i n s e a rch o pe ra t ion s t o r ep re sen t l a rge n umbe r s o f d a ta r e co rd s i n { PO INTS } a nd { S ITES } 7. Two p r imary d a ta f i l e s a r e m a in ta ined . One f i l e , { PO INTS } , c on ta in s t he i n f orma t ion o n t ho se p o in ts c on s t i tu t ing t h e b oundary d a ta , wh i le as e cond f i l e { S ITES } i sc omposed o f r e co rds h o ld ing s pec if ic i n f orma t ion r e la t ing t o i n d iv idua l a r chaeo log ica l s i te s . S i nce t he t wo s e t s o f d a ta s e rve q u i te s epa ra te a nd d i s t inc t f unc t i on s , t he t wo c or re spond ing f i l e s a r e man ipu la ted d if e ren t ly a nd h ave d if e ren t s t ruc t u re s .

F o r i n s tance , t h e d a ta f i l e { S ITES } i sl i ke ly t o b e u pda ted f r equen t ly b ecau se o f

t he a dd i t ion o fn ew s i te s , a nd p e rhap s more r a re ly b ecau se o ft h e d e le t ion o r a l te ra t ion o fe x i s t ing r e cord s . Wh i le i ti sn ece s sary t o a s soc ia te i n d iv idua l s i te sw i th t h e l ow es t l e ve l u n i t i nw h ich t h ey a r e l o ca ted ( norma l ly t he q ua r te r land ) , n o o rde r ing o ft he s i te s w i th in

7

Af u l l d e sc r ip t ion o ft h e f i l e o rgan isa t ion i sg i ven i n t he "De sc r ip t ion o ft h e F i le s" o n p age 5 1

C hap te r 2 : Mak ing t he D a ta A va i lab le

4 8

au n i t i sr equ i red o r , i ndeed , m ean ingf u l . Al i nked l i s t s t ruc tu re w a s t h e ref o re i n co rpo r a ted i n t he { S ITES } f i l e , t o g i ve m ax imum f l ex ib i l i ty w hen a dd ing o r d e le t ing s i te r e c o rd s . W i th t h i s s t ruc tu re e ach r e co rd i n c lude s al i nk v a lue , p o in t ing t o t he n ex t r e co rd i n t h e l i s t o r c ha in s o fs i te s l o ca ted i nt he s am e p r ima ry u n i t . T he re i sa l so a l i nk b e t w een t he c ha in s o fs i te s a nd t h e p r ima ry u n i t o n w h ich t h ey a r e l o ca ted f r om t h e a p p rop r ia te q ua r te r land r e co rd s s t o red i n af i l e c a l led { A DM IN } , ( s ee F igu re 2 4 o n p age 4 8 ) . T he l i nk p o in t s t o t h e f i r s t { S ITES } r e co rd i n ac ha in o fs i te reco rd s s o c onnec ted . S ince a s soc ia ted s i te s a r e c ha ined t oge the r b y l i nk s , t h e r e co rd s o fa l l t he s i te s l o ca ted w i th in a p a r t icu la r u n i t m ay b e s c a t te red t h roughou t t h e f i l e -a s r e co rd s a re a dded o r d e le ted -w i th n o d e t r imen ta l e f ec t s t o t he s y s tem . T he f i l e { PO INTS } h o ld ing t h e b ounda ry p o in t s i n f o rma t ion h a s q u i te d if e ren t c ha rac t e r i s t ic s . Once t he p o in t s c o r re spond ing t o ag i ven b ounda ry h ave b een e n te red i ti s u n l ike ly t ha t a ny n ew p o in t s w i l l b e a dded o r d e le ted . How eve r , t he se r e co rd s a r e l i ke ly t o b e r e t r ieved mo re f r equen t ly , a nd s o al i nked l i s t f i l e s t ruc tu re a s o u t l ined a bove w ou ld h ave f ew o r n o a dvan tage s . F u r the rmo re , e ve ry b ounda ry -po in t f o rm s ac ompo n en t o fa tl e a s t t wo b ounda r ie s s imu l taneou s ly . I tw ou ld t he ref o re b e f a r t oo c o s t ly , i n t e rm s o f s t o rage a nd p roce s s ing t im e , f o r e ach { PO INTS } r e cord t o c a r ry a s t r ing o f l i nk s t o a l l t he p o s s ib le c ha in s o fb oundary p e rmu ta t ion s . S to rage r equ i rem en t s c ou ld b e a s h i gh a s t ho se e nv i saged f o r t he mu l t ip le s t o rage o f p o in t s . B y r emov ing t he l i nk s f r om t he b oundary p o in t s f i l e a l toge the r , a nd t r an sf e r r ing t hem i n to a s epa ra te f i l e , { BOUNDARY } , t h i s p rob lem h a s b een c i rcumven ted . T he t e chn ique i sm ade p a r t icu la r ly ef i c ien t b y e xp lo i t ing t he f a c t t ha t -b ecau se o ft he w ay map s a r e n o rma l ly d i g i t i sed -mo s t p o in t s f o rm ing ab ounda ry w i l l b e g rouped i nb a tche s o fc on secu t ive e n t r ie s i n t h e f i l e { PO INTS } . I n s tead o fh av ing l i nk s p o in t ing t o i nd i v i dua l b ounda ry -po in t r e co rd s , e ach r e co rd i n t he f i l e { BOUNDARY } c on ta in s t wo v a lue s , ap o in te r t o t he F i r s t E n t ry i n { PO INTS } ( FEP ) , h ead ing t he r equ i red l i s t o f e n t r ie s , a nd a no the r v a lue g i v ing t he Numbe r o fr e levan t c on secu t ive E n t r ie s t o b e r e t r iev ed f r om t h e f i l e { PO INTS } ( NEP ) . F o r i n s tance , t he p a i r ( 267 , 1 606 ) i nd ica te s t ha t t he r e a r e 2 67 c on secu t ive e n t r ie s i n { PO INTS } , s t a r t ing w i th e n try n umbe r 1 606 . T he NEP v a lue i ss ome t ime s a ccompan ied b y am inu s s i gn w h ich i n d ica te s t ha t F EP v a lue i sp o in t ing t o t h e b o t tom , a s o ppo sed t o t he t o p , o f t h e r e qu i red l i s t : t he d i rec t ion o f c oun t ing i sd ef ined b y t h e s i gn . A c o mp le te b ounda ry i sf u l ly d ef ined b y as e t o fc on s e cu t ive ly p a i r ed e n t r ie s i n{ BOUNDARY } . Ano the r f i l e , { AD MIN } , c on ta in s t he c omp le te l i s t o f a l t he h i e ra rch ica l u n i t s i n t he s y s tem , i n c lud ing p o in te r s t o t he f i l e { BOUNDARY } t o f a c i l i ta te b oundary d ef in i t ion , a nd t o t he f i l e { S ITES } , p e rm i t t ing s i te r e t r ieva l a nd u pda t ing . { AD M IN } i st he ref o re t he p r inc ipa l f i l e c on t ro l l ing a cce s s t o t he who le s y s tem . Two s ma l l f i l e s , { SUBS } a nd { TEXT } , c omp le te t h e a r rangemen t : { TEXT } , w h ich i s a cce s sed f r om t he f i l e { PO INTS } , s t o re s e x t ra i n f o rma t ion p e r ta in ing t o s pec ia l b ound a ry p o in t s ( e .g . i n te r sec t ion s o fb ounda r ie s ) a s r e qu i red . T he f i l e { SUBS } , a cce s sed f r om t he f i l e { AD MIN } , e nab le s t he t r ee s t ruc tu re i mp l ic i t i nt he h i e ra rchy o fa dm in i s t ra t ive u n i t s t ob e s t o red i n ac onven ien t f o rm . T he f i l e { SUBS } a l so s e rve s o ne o the ri mpo r tan t f unc t ion , h av ing a s ma l l p a r t o fi tr e se rved f o r as imp le d i rec tory . T he f i r s t t en l o g ica l r e co rd s i nt h i s f i l e a r e s e t a s ide f o r t he i nd iv idua l i n dex v a lue s t o t he f i r s t f r ee a va i lab le r e co rd ( l og ica l ) o fe ach o ft h e f i l e s b u i l t i n to t he s y s tem .

I ndex v a lue s t o t he f i r s t f r ee

e n t r ie s i n { BOUNDARY } , { SUBS } , { PO INTS } , { S ITES } , { AD M IN } a nd { TEXT } a r e h e ld i n{ SUBS }( 1 . . .6 ) r e spec t ive ly . E n t r ie s 7t o 1 0a r e l e f t f r ee t o c a te r f o r t he p o s s ib i l i ty C hap te r 2 : Mak ing t he D a ta A va i lab le

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o fa dd i t iona l f i l e s a ts ome l a te r d a te . A dd i t ion s o r d e le t ion s made t o a ny o ft he f i l e s w i l l c au se t h i s i n dex t o b e a d ju s ted a u toma t ica l ly . T o r educe p roce s s ing t ime s s t i l l f u r the r , l o g ica l r e co rd s i ne ach f i l e h ave b een g rouped i n to l a rge r p hy s ica l r e co rd s , a low ing c on s ide rab le s av ing s t o b e made i nt he n umbe r o f d i sc a cce s se s .

B lock ing o fR e cord s I th a s a l ready b een n o ted t ha t t he a cce s s ing o fd i sc f i l e s i sv ery s l ow i nc ompa r i son w i th o pe ra t ion s i nc o re . When t r an sf e r r ing d a ta f r om d i sc t o c o re , t he t ime r equ i red i ss pen t a lmo s t e n t i re ly i nl o ca t ing t he d e s i red r e co rd o n t he d i sc : a cce s s t ime i sd ependen t o nt he s peed o fr o ta t ion o ft he d i sc w i th in i t s d r ive . O nce t he r e co rd i sl o ca ted , t he i n f o rma t ion i sc op ied i n to c o re much f a s te r , v i r tua l ly a tt he s peed o fl i gh t . T he ref o re t he amoun t o f t im e n eeded t o r ead a d i sc r e co rd d epend s v ery l i t t le o n t h e l e ng th o ft he r e co rd i t se lf . D rama t ic s av ing s i np roce s s ing t ime c an t h e ref ore b e a ch ieved i f ,b yu s ing l a rg er r e co rd s , t he n umbe r o fa cce s se s t o t he d i sc c an b e r educed .

L a rge r r e co rd s c an b e f o rm ed b y

c omb in ing s e ve ra l l o g i ca l r e co rd s ( i . e . t he r e co rd s a s d ef ined a nd u sed i n t he p rog ram ) i n to a s i ng le p hy s i ca lb lock , w h ich w i l l b e t he u n i t o ft r an sf e r t o a nd f r om t he d i sc . T h i s t e chn ique i sp a r t icu la r ly e f f ec t ive i nt h is a pp l ica t ion d ue t o t he n a tu re o ft he l o g ica l r e c o rd s : t hey a r e n o rma l ly e n te red i ng roup s a nd u sed i ng roup s . T he r e t r ieva l o fb lock s c on s i s t ing o fg roup s o fc on secu t ive r e co rd s w i l l r e duce t h e n umbe r o ft ime -con sum ing d i sc a cce s s o pe ra t ion s . An o p t imum c omp rom i se h a s t o b e f ound b e tween a cce s s ing e ach i nd iv idua l e n t ry r e q u i red a nd l o ad ing t he e n t i re d a ta b a se i n to m emo ry . I n t h i s s y s tem , f o r i n s tance , a l o g ica l r e co rd i nt he f i l e { BOUNDARY } c on s i s t s o ft wo v a lue s , e ach o ne a 2 -by te i n te g e r ( a p o in te r t o a { PO INTS } r e co rd a nd t he n umbe r o f c on secu t ive r e co rd s i n { PO INTS } t ha t mu s t f o l low i t ) ; a n 8 0 -by te p hy s ica l r e co rd l e ng th h a s b een c ho sen f o r t h e b lock s g roup ing 2 0 s uch r e co rd s . One s uch b lock i sh e ld i nm emo ry i n a2 -by te i n t e ge r a r ray ( def ined a s BND ( 1 . . .40 ) ) , t he i ndex n umbe r o ft h i s b lock i sh e ld i n o ne e l e m en t o fa n a r ray ( def ined a s HERE ( 1 . . .6 ) ) , a nd t he c o r r e spond ing e l emen t o fa n a r ray ( d ef ined a s M OD ( 1 . . .6 ) ) i nd ica te s w he the r o r n o t t h i s b l ock h a s b een u pda ted w h i le i n m emory . T he M OD a r ray a vo id s c opy ing t he b lock c u r ren t ly i nm emory b ack t o d i sc w heneve r a no the r b lock i sr e qu i red , u n le s s a mod if ica t ion h a s t aken p l ace : t he c opy ing o pe ra t ion i so n ly p e rf o rmed i ft h i s b lock h a s b een mod if i ed w h i le i nm emory , a s i nd i c a ted b y t he c o r re spond ing M OD e l emen t b e ing s e t t o / . T he HERE a r ray a vo id s r e t r iev ing t he r equ i red r e co rd i ft h i s i sa l ready i nm emory . T he p rocedu re p e rf o rm ing i npu t /ou tpu t o pe ra t ion s i sI NOUT ( F ILENO , RECNO , READ WRITE ) . T he se p a rame te r s s pec if y w h ich f i l e ( F ILENO ) i sn eeded , t he l o g ica l r e co rd ( RECNO ) i nvo lved , a nd w he the r ar e ad o r aw r i te o pe ra t ion ( READ WR ITE ) i s r equ i red . When F ILENO r e f e r s t o t h e f i l e { BOUNDARY } t he t wo n umbe r s f o rm ing a r e co rd i n t ha t f i l e a r e t r an sf e r red i n to ( f o r READ ) o r f r om ( f o r WR ITE ) t wo m emory l o ca t ion s n amed F EP a nd NEP ; t he s e gmen t o f p seudo -code b e low i s as chema f o r a t yp ica l c ompac t ion r ou t ine , i nt h i s c a se t he { BOUNDARY } s e c t ion . P seudo -code i su sed h e re t o a vo id d e ta i l s o f ap a r t icu la r p rog ramm ing l a nguage :

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I := ( RECNO -1) /20 (Whe re /d eno te s i n tege r d i v i s ion ) J := ( RECNO Ix20 )x2 -1 I := I+ 1( 8) I F I. NE . HERE (F ILENO ) THEN B EG IN I F M OD (F ILENO ) = 1THEN WR ITE (BLOCK I N CORE TO F ILE ) ; READ (BLOCK ( I ) FRO M F ILE ) HERE (F ILENO ) = I MOD (F ILENO ) =0 END I F READ WR ITE = READ THEN B EG IN NEP = BND (J ) F EP = BND ( J +1 ) END ELSE B EG IN BND ( J ) = NEP BND (J+ 1 ) = F EP MOD (F ILENO ) = 1 END RETURN O the r s e c t ion s o ft he p rocedu re a pp ly t o t he o the r f i l e s , w h ich a re o rgan i sed i n as im i la r manne r . A s e xp la ined a bove , t h i s m e thod o fl a y ing o u t t he f i l e s i sv e ry e conom ic w i th t he n umbe r o fd i sc a cce s se s . I ta l so r educe s t he amoun t o fd i sc s t o rage n eeded , s i nce e ach r e co rd o n t he d i sc f i l e ( i n t h i s c a se t he b lock o fl o g ica l r e co rd s ) r equ i re s as t o rage o ve rhead , t o a low i d en t if i ca t ion a nd t o l e ave g ap s b e tween r e co rd s . S uch o ve rhead s a r e t he s ame , i r re spec t ive o ft he l e ng th o ft he r e co rd : t he b l o ck ing o f nl o g ica l r e co rd s r e d uce s s uch d i sc s t o rage o ve rhead s b y af a c to r o fn . T he i mp lem en ta t ion o ft h i s f i l e s y s tem h a s c onf i rmed i t s f l ex ib i l i ty a nd a dap tab i l i ty f o r aw ide r ange o fa pp l ica t ion s , a nd a l so i t s v ery h i gh l e ve l o f ef i c iency i nt e rm s b o th o f s t o rage r equ i rem en t s a nd s peed o fp roce s s ing .

D e sc r ip t ion o ft h e F i l e s T he re i sc on s ide rab le v a r ia t ion i nt h e i n te rna l o rgan i sa t ion o ft he s i x f i l e s . T he g ene ra l a dm in i s t ra t ive f i l e { AD M i s ac o l lec t ion o f 3 2 -by te r e co rd s . E ach r e co rd h o ld s i n f o rma t ion s pec if ic t o o ne p a r t icu la r l a nd -un i t a nd i sf o rm ed b y ag roup o ff i xed leng th

8

B locks a nd r ecords a re n umbe red f r om 1 r a the r t han 0 ; 1i st he b lock n umbe r , . 1i nd ica te s t he p o s i t ion o ft he r equ i red l og ica l r eco rd w i th in t he b lock ( wh ich c on s is t s o f2 0 c onsecu t ive l og ica l r ecords ) .

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f i e ld s . S eve ra l f i e ld s c on ta in d a ta w h i le o the r s s t o re p o in te r s w h ich l i nk t he se r e co rd s t o ad end r i t ic s t ruc tu re o fp o in te r s ( he ld i nt he f i l e s { BOUNDARY } a nd { SUBS }) a l low ing a cce s s t o t he o pe ra t iona l d a ta f i l e s ( i . e . { S ITES } a nd { PO INTS }) . I nf o rma t ion m a in t a ined i n { AD MIN } i n c lude s : t he u n ique c ode n umbe r s f o r e ach u n i t ; ap o in te r n amed ROOT w h ich i d en t if ie s t h e l o ca t ion o ft he i mmed ia te p a ren t o ft h e s pec if ied u n i t ; ap a i r o fv a lue s w h ich i nd ica te w he the r t he u n i t c omp r i se s s ub -un i t s a nd , i fs o , h ow t h e i r l o c a t ion s may b e t r aced t h rough a s e t o fp o in te r s k ep t i nt he { SUBS } f i l e . I n F igu re 2 4 o n p age 4 8 , f o r e xamp le , { AD M IN } r e co rd n umbe r ( i . e . I ) 9h a s t h ree s ub -un i t s . ( Th i s i si nd ica ted b y t he f i e ld NES , o r t he Numbe r o fE n t r ie s i n { SUBS } , s e t t o t h ree ) . T hey l i e i n s ucce s s ive { SUBS } r e co rd s b eg inn ing a t { SUBS .2 } , ( s hown b y F ES , t he i n dex o f t he Numbe r o ft he f i r s t o ft h e se E n t r ie s i n{ SUBS } , b e ing s e tt ot wo ) 9S im i la r ly , as e cond p a i r o fp o in te r s l i nk t he { AD M IN } r e co rd s , v i a t h e f i l e { BOUNDARY } , t o t h e l i s t o f c o -o rd ina te s wh ich c on s t i tu te t h e u n i t ' s b ounda ry ( i n { PO INTS }) . F o r e xamp le , t he b ounda ry p o in t s d ef in ing t h e u n i t h e ld i n { AD M IN .2 } c an b e l o ca ted i nt wo q u ick o p e r a t ion s . F i r s t t ake t he t wo s ucce s s ive e n t r ie s f r om { BOUNDARY .5 } ( i nd ica ted b y NEB , t he n umbe r o fe n t r ie s i n{ BOUNDARY } , b e ing s e t t o t wo , a nd F EB , o r t h e F i r s t { BOUNDARY } E n t ry i n dex n umbe r , b e ing s e t t o f i ve ) . S econd , t ake t he t wo p o in te r s h e ld i n e ach o f t he se { BOUNDARY } r e co rd s a nd p e rf o rm a s im i la r o pe ra t ion . T he c on ten t s o ft he t h ree e n t r ie s i n{ PO INTS 2 . .4 } a r e r e t r ieved i nr e ve r se o rde r( a s t he + / f l ag i nt he c on t ro l l ing { BOUNDARY } r e co rd s i ss e t t o m inu s , NEP i ss e t t o 3a nd F EP i ss e t t o 4 ) .

T he se a r e t h en j o ined t o t he t wo { PO INTS } e n t r ie s b eg inn ing a te n try 1 0

t o c omp le te t he b ounda ry d ef in i t ion . F ou r o the r f i e ld s g i ve t h e l a rge s t a nd s ma l le s t c a s t ing s a nd n o r th ing s f o r e ach u n i t . T he se v a lue s e nab le t he p rog ram t o r e duce t he n umbe r o fp o s s ib le p a ren t u n i t s t ow h ich as i te loca t ion c ou ld b e long , t hu s r educ ing t he t im e n eeded t o s e a rch t he r e cord s a nd make t he m a tch . T he f i l e o fp o in te r s , { BOUNDARY } , c on ta in s t wo e n t r ie s p e rl o g ica lr e co rd , o ne ( c a l led F EP ) i n d ica t ing t he l o ca t ion o f t he f i r s t { PO INTS } r e co rd t o b e r e t r ieved , w h i le t he o the r ( c a l led NEP ) g i ve s t h e n umbe r o fr e co rd s t o b e r e t r ieved . As i ng le p hy s ica l r e cord i n { BOUNDARY } o ccup ie s 8 0 b y te s a nd c on ta in s 2 0 l o g ica l r e co rd s ( s ee Append ix 1 ) . { SUBS } i sa no the r i n te rmed ia te p o in te r f i l e , u sed t o s pec if y t he s ub -un i t s o fe ach u n i t i n t he h i e ra rch ica l t r ee s t ruc tu r e . E ach l o g ica l r e co rd c on s i s t s o f ap o in te r t o a n { AD MIN } e n try , as e t o fc on secu t ive r e co rd s c o r re spond ing t oa l l u n i t s t ha t a r e s ub se t s o fe ach p a ren t u n i t . A s i ng le p hy s ica l r e co rd i n { SUBS } o ccup ie s 8 0 b y te s a nd c on ta in s 4 0 l o g ica l r e co rd s . T he f i l e { PO INTS } s t o re s t he s e lec ted b ounda ry p o in t s a s al i s t o f c o -o rd ina te s . E ach e n t ry o r l o g ica l r e cord i n { PO INTS } c on ta in s at we lve -f igu re g r id r e f e rence ( XN a nd YN c o mb ined ) , t oge the r w i th a s i x -f igu re i n tege r f l ag w h ich d ef ine s t he p o in t ' s t ype ( T ) . F o r i n s tance a b ounda ry p o in t m igh t b e d i s t ingu i shed a s r ep re s e n t ing a n i n te r sec t ion . T he { PO INTS } f i l e a l so u se s t he se f l ag s t oa cce s st he { TEXT } f i l e w h ich c on ta in s m i sce l laneou s i n f o rma t ion r e levan t t op a r t icu la rp o in t s . As i ng le p hy s ica l r e co rd i n{ PO INTS } o ccup ie s 1 20 b y te s a nd h o ld s ab lock o f2 0 i nd iv idua l e n t r ie s . A l though t h e d i g i t i sa t ion a nd s t o rage o fb ounda ry p o in t s h a s b een made a s ef i c ien t a s p o s s ib le , t he f i l e { PO INTS } c an s t i l l b e l a rge i nc ompa r i son t o t he o the r f i l e s . F i le s i ze i n t h i s c a se i se f ec t ive ly d e te rm ined b y t he c omp lex i ty a nd s c a le o f t he o r ig ina l b a se m ap s c oup led w i th t he d e s i r ed d eg ree o f r e so lu t ion . Obv iou s ly , r e co rd ing b oundary -

9

T he p o in te r s i n FES a nd NES a re u sed t o r e f e r t o t h e d ependen t ( S ITES ) r ecord s . T he p rog ram k now s w hen t h e f i e ld r e f e r s t o ( SUBS ) o r ( S ITES ) b ecau se a no the r f i e ld r ecords w he the r t h e u n i t i sp r imary o r n o t .

I fi ti st hen t he re c an b e n o s ub -un i t s , a nd t he p o in te r s mus t r e f e r t o t h e s i te s . C onve r se ly , p o in te r s

t o t h e f i l e ( S ITES ) a re o n ly f ound i np r imary u n i ts ) .

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p o in t s a t o ne -m i l l ime t re i n te rva l s , f o r e xamp le , w ou ld g ene ra te a { PO INTS } f i l e f i ve t im e s l a rge r t han t he s ame b ounda ry r e co rded a ti n te rva l s o fh a lf -cen t ime t re s . Al o g ica l r e co rd i n { S ITES } i ss p l i t i n to f ou r f i e ld s . F i e ld s o ne a nd t wo c on ta in g r id r e f e rence s , d e f in ing t he l o ca t ion o ft h e s i te . An ume r ica l c ode i nt he t h i rd f i e ld g i ve s t he g ene r ic t ype o ft h e s i te , w h i le i nt he f ou r th f i e ld ( LNK ) t he re i s an ume r ica l p o in te r t o t he n ex t s i te r e co rd , l o ca ted o n t he s ame p r ima ry u n i t . O ne p hy s ica l r e co rd i n { S ITES } w i l l o ccupy 1 60 b y te s c on ta in ing ab lock o f1 0l o g ica l r e co rd s . An e xamp le o ft he d a ta s t o red f o r t he t r een o f Knok sewe l l ( i n t h e No r th s ide p a r i sh o fJ u rby ) a nd i t s c on s t i tuen t q ua r te r land s i sg i ven i nt he n ex t s e c t ion .

S pe c if y ing H ighe r L e ve l U n i t s One o ft he mo s t s i gn if ican t a dvan tage s o ft h i s d a ta s t ruc tu re i st ha t t he re i sn o n eed t o d i g i t i se t he b oundary o fa ny h i ghe r l e ve l u n i t ( e .g . i nt he c a se o ft he I s le o f Man , at r een o r ap a r i sh ) w h ich i sf o rmed f r om l owe r l e ve l u n i t s ( e .g . q ua r te r land s ) w h ich a r e a l r eady e n te red i nt he s y s tem . T h i s f e a tu re e n su re s t ha t i n f o rma t ion d e r ived f r om t he i n i t ia l d a ta s e t i si n te rna l ly c on s i s ten t . S i nce c ommon s e gmen t s o fb oundary a r e d ef ined b y e xac t ly t he s ame s e t s o fp o in t s , t h e p o s s ib i l i ty o fc umu la t ive d i sc repanc ie s wh ich w ou ld a r i se i f b ounda r ie s h ad t o b e r e -d ig i t i sed a r e e l im ina ted . T he a ccu racy o ft he d a ta , t ha t i sh ow c l ose ly t hey r ep re sen t t he r e a l s i tua t ion , i ss t i l l v ery much d ependen t u pon t he q ua l i ty o ft he o r ig ina l b a se -map s a nd t he manua l d ex te r i ty a nd r i gou r o ft he p e r son r e spon s ib le f o r d i g i t i s ing t hem . Once a l t he p r ima ry l a nd -un i t s h ave b een r e co rded a nd e n te red i n to t he s y s tem , n o n ew b ounda ry -po in t c o -o rd ina te s n eed t ob e g ene ra ted o r s t o red i no rde r t ha t h i ghe r leve l u n i t s m ay a l so b e c o mpu te r i sed .

I n s tead o fr ep roduc ing p o ten t ia l ly

e x ten s ive l i s t s o fc o -o rd ina te s , al e s s c umbe r some s e t o fp o in te r sw i l l b e a ppended t ot he { BOUNDARY } f i l e , w he re e ach p a i r o f p o in te r s ( NEP a nd F EP ) a bb rev ia te t he a d d re s se s o fg roup s o ft he much l a rge r c o -o rd ina te r e co rd s h e ld i nt he f i l e { PO INTS } . T he c o s t o fo ve rhead s i sr educed a cco rd ing ly . When a u n i t c on s i s t s o fs e ve ra l s ub -un i t s , t h i s i n f o rma t ion c an b e e n te red i n to t he f i l e s y s tem u s ing a q ue ry l a nguage f a c i l i ty . T he s y s tem f i r s t a sk s t he u se r f o r t he n umbe r o fs ub -un i t s a nd t hen t he { AD M IN } n umbe r s o ft he r e levan t s ub -un i t s , a nd e n te r s t hem i n to t h e f i r s t f r ee l o ca t ion s i nt he f i l e { SUBS } . T he p rog ram d e te rm ine s t he i ndex o ft he f i r s t r e levan t e n try i n t he f i l e { SUBS } . T h i s i n f o rma t ion i se n te red i n to t he { AD M IN } r e co rd o f t he h i ghe r leve l u n i t .

T hen , w hen t h e u se r w i she s t o g ene ra te t he a c tua l

b ounda ry f o r t h i s u n i t , t h e o n ly i n f o rma t ion r equ i red f r om t he u se r i st he n ame o ft h i s u n i t . T he m e thod u sed i sb e s t d e sc r ibed w i th r e f e rence t o as imp le b u t r e a l c a se , w h ich w a s i n c luded i nt he t e s t s f o r t he s ub rou t ine DEFBND . T he t r een Knok sew e l l c on s i s t s o ff ou r q ua r te r land s : B a l la tea re , B a l la sa l la , C ronk Moa r a nd We s t Napp in ( F igu re 2 5 o n p age 5 4 ) .

T he se q ua r te r land s w e re d i g i t i sed a nd i n -

s e r ted i nt he s y s tem a s p a r t o ft he c o mpu te r i sa t ion o ft he m ap o fJ u rby . T he r e levan t i n f o rma t ion i n c luded i nt he f i l e s f o l low s . Qua r te r land B a l la tear e : R eco rd 2 00 o ff i l e { AD M IN } r e f e r red t o t h i s u n i t a nd t he ( NEB , F EB ) p a i r o fv a lue s w a s ( 1 , 1 0 1) ; t ha t i s , t he re w a s o n ly o ne c o r re spond ing e n try i n{ BOUNDARY } , a nd i t s e n t ry n umbe r w a s 1 0 1 . T he p a i r o fv a lue s ( NEP , F EP ) a tt h i s e n t ry i n { BOUNDARY } C hap te r 2 : Mak ing t he D a ta A va i lab le

5 3

w a s ( 57 1 , 1 00 1) , i . e . t he re a re 5 7 1 c on secu t ive b oundary p o in t s l i s ted i n t he f i l e { PO INTS } , s t ar t ing f r om e n t ry n umbe r 1 00 1 ( i . e . 1 00 1 . . .157 1) .

Quar ter land B a l la sa l la : R ecord 2 0 1 o f{ AD MIN } i n c lude s ( NEB , F EB ) v a lue s ( 2 , 1 02 ) , p o in t ing t o t wo e n t r ie s i n { BOUNDARY } s t a r t ing f r om 1 02 . T he t wo { BOUNDARY } e n t r ie s 1 02 a nd 1 03 c on ta in t he p a ir s ( 455 , 1 572 ) a nd ( 291 , 1 529 ) , i nd ica t ing t ha t t he re a re 4 55 b oundary p o in t s s t a r t ing f r om t he { PO INTS } e n try 1 572 , f o l lowed b y t he 2 91 p o in t s i nt he e n t r ie s f r om 1 529 d own t o 1 239 . I t may b e n o t iced t ha t t he s y s tem h a s a vo ided r epea t ing i n { PO INTS } t he 2 91 p o in t s 1 239 . . .1529 , wh ich h ad a l ready b een e n te red f o r q ua r te r land

Quar ter land C ronk Moar : T he c or re spond ing r e cord n umbe r 2 03 i n { AD MIN } h a s ( NEB , F EB ) v a lue s ( 2 , 1 04 ) . T he t wo { BOUNDARY } e n t r ie s 1 04 a nd 1 05 c on ta in t h e ( NEP , F EP ) p a i r s ( 155 , 2 027 ) a nd ( 123 , 1 728 ) , i nd ica t ing t ha t t he re a r e 1 55 e n t r ie s i n { PO INTS } b eg inn ing a t r e co rd 2 027 , f o l lowed b y t he 1 23 e n t r ie s f r om 1 728 d own t o 1 606 . C hap te r 2 : Mak ing t he Da ta A va i lab le

5 4

Quar ter land We s t N app in : R eco rd 2 04 i n t he f i l e { AD M I N } h a s ( NEB , F EB ) v a lue s ( 3 , 1 06 ) . T he t h ree { BOUNDARY } e n t r ie s 1 06 , 1 07 a nd 1 08 c on ta in t h e ( NEP , F EP ) p a i r s ( 404 , 2 182 ) , ( 153 , 1 880 ) a nd ( 79 , 2 18 1) , i nd ica t ing t ha t t he re a r e 4 04 e n t r ie s i n { PO INTS } s t a r t ing a te n t ry 2 182 , f o l lowed b y t he 1 53 e n t r ie s f r om 1 880 d own t o 1 728 , a nd t hen t h e f u r the r 7 9 e n t r ie s f r om 2 181 d own t o 2 103 . T he f i r s t o pe ra t ion t o b e p e rf o rmed t o d ef ine t h e T reen o f Knok sew e l l i st o e x tend t he f i l e { SUBS } w i th t he f ou r v a lue s 2 0 1 , 2 02 , 2 03 a nd 2 04 p o in t ing t ot he { AD MIN } e n t r ie s f o r t h e f ou r c o mponen t q ua r te r land s ; t he r e levan t s e c t ion o f t he p rog ram i n f o rm s t he u se r t ha t t he se v a lue s h ad b een a dded s t a r t ing f r om { SUBS } e n t ry n umbe r 2 75 . T he u se r c an t h en e x tend t he f i l e { AD M I N } b y s pec if y ing t h e k nown d a ta o n t r een K nok sewe l l , i n c lud ing t he ( NES , F ES ) v a lue s ( 4 , 2 75 ) , p o in t ing t o t h e 4e n t r ie s i n { SUBS } s t a r t ing f r om 2 75 . T he f u l l s pec if ica t ion o ft h e b oundary o ft he t r een c an t h en b e r eque s ted b y s e lec t ing t he a pp rop r ia te m enu o p t ion a nd e n te r ing t he n ame o f t h e t r een . T he p rog ram c a l l s t he s ub rou t ine DEFBND , w h ich d ef ine s t he b ounda ry o ft he t r een , s t o re s t he a pp rop r ia te i n f o rma t ion i n{ BOUNDARY } a nd c omp le te s t he { AD M I N } r e co rd f o r t h i s t r een w i th t he ( NEB ,FEB ) p o in te r s a nd t he m ax imum a nd m in imum v a lue s o f t he X a nd Y c o o rd ina te s . T he m e thod o f o pe ra t ion e mbod ied i n DEFBND c an b e s t b e d e sc r ibed b y d i s t ingu i sh ing t h ree s t age s .

STAGE 1-R econ s truc t ing t he B ounda r ie s o fA l l t h e C omponen t Un i t s T he f i r s t o pe ra t ion p e rf o rmed b y t he DEFBND r ou t ine i st he i d en t if i ca t ion o f t he b ounda r ie s o fa l l t he c omponen t u n i t s . I tt hen e s tab l i she s w h ich s t re tche s o fb ounda ry a r e c o mmon t o mo re t han o ne s ub -un i t a nd a r e t h e ref o re i n t erna l p a r t i t ion s t o b e e l im i n a ted . T o d o t h i s t he re i s n o n eed t o a cce s s t he a c tua l c o -ord ina te s s t o red i n { PO INTS } , s i nce t he b ounda r ie s a r e f u l ly d ef ined b y t h e e n t r ie s i n { BOUNDARY } . I n s tead t he b ounda ry i n f o rma t ion i sr e con s t ruc ted i n as e t o ff i ve s ho r t a r ray s ; t h e d i m en s ion o f t he se a r ray s n eed s t o b e o n ly a s l ong a s t he max imum n umbe r o f { BOUNDARY } e n t r ie s i n c luded i nt he s ub -un i t s c o mp r i s ing t he h i ghe ru n i tr equ i red , i . e . n o mo re t han , s ay , 5 0 e l emen t s . T he f i ve a r ray s u sed -F IRST , LAST , BEFORE , AFTER a nd I NDEX -w i l l c on ta in t he f o l low ing i n f o rma t ion c o r re spond ing t o e ach { BOUNDARY } e n try : -F IRST :t he l owe s t ( PO INTS )-en t ry -numbe r o ft h i s s t re tch . -LAST :t he h ighe s t ( PO INTS )-en t ry -numbe r o ft h i s s t re tch . -BEFORE : t he ( PO INTS )-en t ry -numbe r o ft he p o in t n ex t t o F IRST i nt he LAST t o F IRST d i rec t ion . -AFTER: t he ( PO INTS )-en t ry -numbe r o ft he p o in t n ex t t o LAST i nt he F IRST t o LAST d i rec t ion . -I NDEX :t h is i su sed t o r ank t he e l emen t s .

As imp le s o r t i n se r t s i nt he a r ray I NDEX t he i n d ice s o ft he e n t r ie s r anked i na s cend ing o rde r o ft he v a lue s i n F IRST . T he max imum a nd m in imum v a lue s o ft h e Xa nd Y c o o rd ina te s a re a l so d e te rm ined a tt h i s s t age , a s t h ey w i l l b e t he l a rge s t a nd s ma l le s t v a lue s C hap te r 2 : Mak ing t he Da ta A va i lab le

5 5

g i ven i nt he { AD M I N } e n t r ie s o ft he c omponen t u n i t s . c on ten t s o ft h e a r ray s a tt he e nd o fS tage Iw i l l b e : L ine no.

I n t he e xamp le c on s ide red t h e

BEFORE FIRST LAST AFTER INDEX

1 2 3

1 571 1 239 1 572

1 001 1 572 1 239

1 571 2 026 1 529

1 001 1 529 2 026

1 3 2

Ballateare Ballasalla

4 5

1 606 2 027

2 027 1 606

2 181 1 728

1 728 2 181

5 7

Cronk Moar

6 7 8

2 103 2 181 2 182

2 182 1 728 2 103

2 585 1 880 2 181

1 880 2 585 1 728

4 8 6

West Nappin

I t

I f

n I t

T ab le 2 . 1 . T he v a lue s i n I NDEX i nd ica te t ha t t he r ow s mu s t b e a cce s sed i n t he s equence 1 , 3 ,2 ,5 ,7 ,4 ,8 ,6 t o b e i na s cend ing o rde r i nr e spec t o ft he v a lue s i nF IRST .

S TAGE 2-E l im ina t ion o ft h e I n te rna l B ounda r ies A l l t he F IRST -LAST o ve r lap s r ep re sen t s t re tche s o fb ounda r ie s b e tw een t he s ub -un i t s , w h ich t he ref o re c anno t b e p a r t o ft he e x te rna l b ounda ry o ft he h i ghe r leve l u n i t u nde r c on s ide ra t ion . DEFBND a c t iva te s al oop f o r I = 2t o N , whe re N i st he n umbe r o f e n t r ie s i ne ach a r ray ( i n o u r e xamp le N= 8 ) , c o mpa r ing F IRST ( INDEX ( I ) ) w i th LAST ( INDEX ( I -1) ) . I n o u r e xamp le , t he c ompa r i son f o r I= 2w i l l b e b e tween F IRST (3 ) a nd LAST ( 1) ( i . e . 1 239 a nd 1 57 1) . When t he v a lue o fF IRST i sg r ea te r t han t ha t o f LAST , t he r e i sn o o ve r lap a nd t h e l oop i sr e -en te red f o r t he n ex t v a lue o fI .O therw i se , t he f o l l ow ing o pe ra t ion s a r e c a r r ied o u t : •

T he v a lue s i n t he t wo r ow s i n d ica ted b y I NDEX ( I ) a nd I NDEX ( I -1) o fa l t h e f i r s t f ou r a r ray s a r e r e ad ju s ted , s o a st oe l im ina te a l l t he c o mmon v a lue s . I n t h i s e xamp le , ( f o r I= 2 ) , t he p o in t s f r om 1 239 t o 1 529 a r e c ommon t o t wo b ounda r ie s a nd a r e t he r ef or e i n te rna l ; l i ne s 1a nd 3a r e r e ad ju s ted t o e l im ina te t he se p o in t s : L ine no.

•

BEFORE F IRST LAST AFTER INDEX

1

1 571

1 001

1 238

1 239

1

3

1 529

1 530

1 571

1 001

2

S e t t ing NE W = F IRST ( INDEX ( I ) )+ 1 ,a l l t he s ub sequen t e l emen t s i n F IRST a r e s c anned , a nd t ho se v a lue s s ma l le r t han NE W a r e r ep laced w i th NE W . Wheneve r t h i s i sd one t he c o r re spond ing v a lue o f BEFORE i sr e se t t o NE W -1 . T h i s o pe ra t ion e l im ina te s a ny o the r s t re tche s o f b ounda ry o ve r lapp ing c ommon s e c t ion s a l ready e l im ina ted i nt he p rev iou s o pe ra t ion .

•

E l im ina t ion o fa l t he r ow sw he re F IRST i sn ow g r ea te rt han LAST . T he e l im ina t ion i sp e rf o rmed v ery s imp ly . I fr ow I NDEX (J ) h a s t o b e e l im ina ted , a l l t h e r ow s o f I NDEX f r om J+ 1t o N a r e s h if ted o ne p l ace u p ; t h e e l im ina ted v a lue p rev iou s ly i n I NDEX ( J ) i ss aved i nI NDEX (N ) , s o t ha t ar e co rd i sk ep t i nc a se af a i lu re c ond i t ion o ccu r s l a te r o n , a nd N i sd ec remen ted b y o ne .

C hap te r 2 : Mak ing t he Da ta A va i lab le

5 6

I n t h e g i ven e xamp le t h e s i tua t ion a tt he e nd o ft h i s s t age i sa s f o l low s : L ine no. 1 2 3

BEFORE F IRST LAST AFTER INDEX 1 571 1 239 1 529

1 001 1 572 1 530

1 238 1 605 1 571

1 239 1 606 1 001

1 3 2

4

1 606

2 027

2 102

2 103

5

5 6

1 880 2 103

1 881 2 182

2 026 2 585

1 529 1 880

4 6

7 8

1 880 2 181

1 881 2 182

1 880 2 181

2 585 1 728

8 7

N = 6 T ab le 2 . 2 . T he v a lue s a bove s how t ha t l i ne s 7a nd 8 h ave b een e l im ina ted : s i nce N= 6 ‚ o n ly t he r ow s i nd ica ted b y t he f i r s t 6r ow s o fI NDEX a r e t o b e t aken i n to a ccoun t , i . e . r ow s 1 , 3 , 2 , 5 , 4a nd 6 . I t c an b e s e en t ha t n o o ve r lap s o ccu r b e tw een t he se r ema in ing F IRST -LAST s t re tche s .

S TAGE 3 -D e te rm ina t ion o f aC on t inuou s B ounda ry f o r t h e N ew Un i t DEFBND s t a r t s w i th t he r ow p o in ted b y I NDEX (I) ( i n t h e e xamp le t h i s i sr ow 1 ) , a nd s ave s t he BEFORE a nd F IRST v a lue s , f o r c heck ing a t t h e e nd t ha t t he b oundary i s c l o sed . T he p rog ram t hen s e a rche s t o f i nd a ma tch b e tween t he LAST a nd /o r AFTER v a lue s o f t h i s r ow a nd t he v a lue s i n t he r ema in ing l i ne s , s o a s t o d e te rm ine h ow t he b ounda ry c on t inue s . When a c on t inua t ion ma tch i sf ound t he a pp rop r ia te a c t ion i s t aken a nd t he l i ne i se l im ina ted , w i th t he m e thod s hown i n s t age 2 . T h i s p roce s s c on t i nue s u n t i l a l l r ow s a r e e l im ina ted . A t t he e nd t h e p rog ram c heck s t ha t t he l a s t v a lue s ma tch t ho se s aved a tt he s t a r t , h ence c l os ing t he b oundary ' ° . I n t he g i ven e xamp le , t he p roce s s s t a r t s w i th l i ne 1 ,w i th t he p o in t s ( 100 1 . . .1238 ) ; am a tch i sf ound b e tw een AF TER o ft h i s r ow a nd BEFORE o fr ow 2 ,s o t h e b ounda ry i sc on t inued w i th t he p o in t s ( 1239 ) a nd ( 1572 . . .1605 ) ; t h e n ex t ma tch i sw i th t h e BEFORE o fr ow 4 , s o t he p o in t s i n c luded a r e ( 1606 ) a nd ( 2027 . . .2 102 ) ; t he n ex t m a tch i sw i th t he BEFORE o fl i ne 6 ,f o r t he p o in t s ( 2 103 ) a nd ( 2 182 . . .2585 ) ; t he n ex tm a tch , w i th t h e BEFORE o fl i ne 5i nd ica te s t he p o in t s ( 1880 ) a nd ( 1 881 . . .2026 ) ; t he f i na l m a tch i sw i th BEFORE o fr ow 3 ,i nvo lv ing t he i n c lu s ion o ft h e p o in t s ( 1 529 ) a nd ( 1530 . . .157 1) . T he f i na l c heck s how s t ha t t he l a s t v a lue , 1 57 1 , i st h e s ame a s t he f i r s t BEFORE ; t he r ef o re t h e b ounda ry i sc l o sed . At o ta l o fs i x { BOUNDARY } e n t r ie s a r e g ene ra ted ( s ee T ab le 2 . 3 b e low ) . T he se a r e e n te red a t t h e f r ee e nd o ft he { BOUNDARY } f i l e , i n t h i s c a se , t h e e n t r ie s 4 48 . . .453 , a nd t he c o r re spond ing NEB a nd F EB v a lue s ( i n o u r e xamp le 6 a nd 4 48 ) a r e i n c luded i n t he { AD M I N } e n t ry f o r t h i s n ew u n i t , t oge the r w i th t h e m ax imum a nd m in imum v a lue s o f Xa nd Y d e te rm ined i ns t age 1 .

1 0

I ff o r s o me r ea son t h e b oundary f a i ls t o c l o se , a me s sage i ss en t t o t h e u se r . I n s uch e ven t s t h e u se r h a s t h e o p t ion o fs w i tch ing o n ad i agno s t ic f a c i l i ty w h ich t r ace s t h ep rog re s s o ft h e p rog ram i np u t t ing t oge the r t h e u n i t s . T he t r ace c an b e w r i t ten t o t h e s c reen o r a n o u tpu t f i l e f o r e xam ina t ion a t al a ter d a te .

C hap te r 2 : Mak ing t h e Da ta A va i lab le

5 7

NEP 2 39

FEP 1 001

3 5 7 7

1 572 2 027

4 04

2 182

1 47

1 880

4 3

1 529

T ab le 2 . 3 T he n ew u n i t , i nt h i s c a se t he t r een K nok sewe l l , i sn ow f u l ly d ef ined w i th in t h e s y s tem a nd c an b e a cce s sed f o r a ny p u rpo se ( f o r e xamp le , p lo t t ing , c a lcu la t ion o fa r ea , o r c a l c u la t ion o fd i s tance s f r om s i te s ) . I t may b e n o ted t ha t i n t he e xamp le g i ven a bove t h e n ew u n i t r equ i re s o n ly s i x { BOUNDARY } e n t r ie s i no rde r t o b e f u l ly d ef ined , i . e . 6x2x2 = 2 4 b y te s o fs t o rage . I f ad i rec t m e thod h ad b een u sed , i tw ou ld h ave b een n ece s sary t o d i g i t i se a nd s t o r e 2 39 + 3 5 +7 7 +4 04 + 1 47 + 4 3 =9 45 p o in t s , r equ i r ing as t o rage o f 3x4x9 45 = 1340 b y te s f o r Xa nd Y c o -o rd ina te s a nd p o in te r / type d ef in i t ion , p lu s a ny a dd i t iona l t e x t i n f o rma t ion . T he s av ing i nt ime a nd s t o rage i si mp re s s ive .

R ecord ing a nd S tor ing a T heore t i ca l L and -S y s tem T he p rocedu re f o l low ed b y t he u se r t o d i g i t i se as y s tem o fl a nd u n i t s i sn ow s t ra igh tf o r w a rd . ( s ee , h ow eve r , " D ig i t i s ing t he B ounda r ie s" o n p age 6 0 f o r a n a ccoun t o ft h e d i f f i cu l t ie s o f m in im i s ing t he e f ec t o f e r ro r s b y t he u se r ) .

I n e s sence i tc on s i s t s o f t he

r e g i s t ra t ion o f t he d e s i red p o in t s o n at ab le t d i g i t i se r . B oundary p o in t s w i l l g ene ra te l o ca t iona l c o -o rd ina te s a nd a n i d en t if y ing f l ag ( o r m a rke r ) n o rma l ly s e t t o ad ef au l t v a lue . O the r p o in t s c an b e s i ng led o u t a nd d i s t ingu i shed f o r s pec if ic r e a son s . U s ing t he h ypo the t ica l e xamp le i lu s t ra ted i n F igu re 2 6 o n p age 5 9 a nd F igu re 2 7 o n p age 6 0 , a u se r m igh t w i sh t o b eg in r e co rd ing t h i s l a nd s y s tem w i th u n i t A .

I n i t ia l ly s t o red i n

m emory , t he e n t i re s e t o fe n t r ie s f o rm ing a ni nd iv idua l u n i t a r ew r i t ten t od i sc a s ab a tch . I nd iv idua l b a tche s a r e s epa ra ted b y t e rm ina to r s w r i t ten a s an ega t ive n umbe r .

F o r i n -

s t ance , c on s ide r t he c a se w he re a u se r s t a r t s d i g i t i s ing u n i t A a t t he p o in t l a be l led I . P o in t Ii s ar e cogn i sab le i n te r sec t ion , n o t at yp ica l b ounda ry p o in t , a nd a dd i t iona l d e t a i l s c once rn ing t he p o in t s hou ld b e r e co rded . I n t he f i r s t i n s tance t h i s i n f o rma t ion w i l l b e h e ld i n a n i n te rmed ia te f i l e s uch a s t ha t i n F igu re 2 7 o n p age 6 0 .

E ven tua l ly , t he se

s upp lemen ta ry d e ta i l s w i l l b e s t o red i nt he s y s tem s f i l e { TEXT } , w i th an o te o ft h e i r l o c a t ion i n t h i s f i l e b e ing p l aced i n t he a s soc ia ted r e co rd s i n t he { PO INTS } f i l e .

When

d i g i t i s ing , p o in t Ii sh i gh l igh ted b y s e t t ing i t s ma rke r t o 1 00 a nd d a ta d e sc r ib ing t he p o in t a r e a dded u s ing s t anda rd i sed n o ta t ion . F o r e xamp le , t he s t a r s ymbo l (* ) i n t he r e co rd f o r p o in t I( r ef e r t o F igu re 2 7 o n p age 6 0 ) m ean s t ha t t h i s p o in t m a rk s a n i n te r sec t ion ; t he s ucceed ing g roup s o f c ha rac te r s a r e t h e n ame s o f t ho se u n i t s whose b ounda r ie s i n te r sec t a tt h i s p l ace . Az e ro i su sed t o c l o se t h e e n t ry . T he s e cond p o in t t o b e d i g i t i sed w ou ld b e p o in t 2w h ich i s an o rma l b oundary p o in t r e qu ir ing n o f u r the r d a ta . T he m a rke r i nt h i s r e co rd w i l l d ef au l t t ot he v a lue o f 2t os how t h i s . P o in t 3i sa no the r i n te r sec t ion . Once a ga in as t a r , p lu s t he n ame s o ft h e c on jo in ing u n i t s , w i l l b e e n te red i n to t he a pp rop r ia te i n te rmed ia te d a ta r e co rd . T he u se r c on t inue s C hap te r 2 : Mak ing t h e Da ta A va i lab le

5 8

1 9

2 0 2 4

3 2 1

2 4

A 8

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5

1 3

25

2 2

6

1 4

7

23

28 27

9

1 5

2 6

1 2

1 6 1 0 1

F igure 2 6 .

1 8

1 7

29 30

T heo re t ica l L and S ys tem

t o f o l low t h i s p rocedu re u n t i l t he c omp le te b oundary o fu n i t A( po in t s 1 . .8 ) h a s b een r e co rded . Now u n i t Bc an b e d i g i t i sed . C o mmenc ing a t p o in t 9 ,t he s ame p rocedu re i sf o l lowed . E x t ra d a ta a r e n eeded a t p o in t 1 0 , w h ich a c t s a s t he i n te r sec t ion p o in t b e tw een t he b ounda r ie s o fu n i t s Ba nd C . When t he u se r r e ache s t ha t s egmen t o fb ounda ry wh ich r un s b e tw een u n i t s Aa nd B , n o r e -d ig i t i sa t ion o ft he s e gmen t i sn ece s sa ry . I n s tead , t he u se rh a s o n ly t o ma rk b o th e nd s o ft he r equ i red s t re tch o fb ounda ry a nd o ne o the rn oda l p o in t o n t he p e r ime te r o f u n i t A ( i . e . p o in t s Ia nd 7 ,a nd , s ay p o in t 3 ) . T he se t h ree r e ad ing s w i l l b e ma rked b y c ode s i nd ica t ing t o t h e p rog ram t ha t as t re tch o fb oundary a l ready s t o red i nt he s y s tem mu s t b e f ound a nd r e f e renced f o r t h i s u n i t . T he f i r s t p o in t o ft h e r equ i red s e c t ion ( I ) i si nd ica ted b y ap lu s s i gn (+ )a ccompany ing t he n ame o ft he u n i t f r om w h ich t he s t re tch o fb oundary w a s o r ig ina l ly d i g i t i sed ( A ) . T he e nd p o in t ( 7 ) o ft h e s e gmen t i sd i s t ingu i shed b y am inu s s i gn ( ) a l so w i th t he s ame u n i t 's n am e . A f i na l p o in t ( 3 ) i s ma rked w i th a s o l idu s ( / ) f o l lowed b y t he n ame o f a ny o the r u n i t i n te r sec t ing w i th t he o r ig ina l u n i t a tt h i s p o in t ( e .g . u n i t D ) .

T he t h i rd r e ad ing e nab le s

t h e p rog ram t o d e te rm ine t h e c or rec t r ou te i ts hou ld t ake i n g a the r ing t he p o in t s i n b e tw een t he i nd ica ted t e rm ina l s ( i n t h i s c a se , p o in t s 1a nd 7 ) , s i nce i tw ou ld o therw i se b ep o s s ib le t op roceed e i the ri nt he d i rec t ion 1 8 -7 o r , a l te rna t ive ly , 1 2 -3 -4 e t c . I ts hou ld a l so b e m en t ioned t ha t i ti sn o t n ece s sary t o e n su re a b so lu te a ccu racy when r e f e r r ing t o t h e i n te r sec t ion p o in t s , a s t h e p rog ram a l low s ar e a sonab le amoun t o ft o le rance i nt he i d en t if ica t ion o fc ommon p o in t s . T he p rog ram u se s t h i s i n f orma t ion s pec if y ing c ommon p o in t s o n ly t o l o ca te c ommon s t re tche s o fb ounda ry . None o ft h i s i n f o rma t ion -i . e . a ny r e co rd s a ccompan ied b y e x t ra d a ta c on ta in ing ap lu s , m inu s o r s o l idu s -w i l l b e s t o red i nt h e s y s tem f i l e s . C hap te r 2 : Mak ing t he Da ta A va i lab le

5 9

M ARKER 8 1 0 0 2 1 0 0 2 1 0 0 2 1 0 0 2 7 2 1 0 0 2 2 1 0 0 1 0 0 1 0 0

F igure 2 7 .

X

XTRA D ATA Y E

1 0 0 1 0 0 1 2 0 1 3 0 1 2 8 1 2 5 1 5 1 0

5 0 7 7 8 5 7 5 5 5 4 7 4 5 4 6

1 3 0 1 3 2 9 7 9 5 1 0 0 1 4 1 2 0

3 5 1 0 1 0 3 0 4 9 4 5 8 4

I n te rmed ia te Da ta F i le :

3 I E

A B0

»A D 0 «A D C 0 N EA C B 0

»BC 0 +A -A /D

D ESCR IPT ION N 9 O F P O INTS P O INT 1 P O INT 2 P O INT 3 P O INT 4 P O INT 5 P O INT 6 P O INT 7 P O INT 8 N I ° O F P O INTS P O INT 9 P O INT 1 0 P O INT 1 P O INT 1 2 P O INT 1 P O INT 7 P O INT 3

I n e n t ry n umber 1 i n t he e xamp le d a ta f i l e , t he s t ar s ymbo l ( * )

means t ha t ap o in t i sa n i n ter sec t ion . The s ucceed ing c harac ter s a re t he n a me s o ft h e u n i t s whose b oundar ie s i n ter sec t a t t h is p o in t ( r ef e r t o p rev ious f i gure ) . T he e n t ry i st e rm ina ted w ith a z ero . I n t he l a s t t h ree e nt r ie s t he s y mbo ls + , ,a nd / ,p o in t t o as t re tch o fb oundary wh ich i sc om mon t o u n i t A .

D ig i t i s ing t h e B ounda r i e s B ef o re t h e d i g i t i sed p o in t s d e sc r ib ing ab ounda ry o rs i te loca t ions a r e s t o red o n d i sk t h ey mu s t b e c onve r ted f r om t he c o -o rd ina te s y s tem o ft h e t ab le t d i g i t i se r i n to t h e a pp rop r i a t e map r e f e rence s . I n p r inc ip le , t h e t e chn ique f o r p e rf o rm ing t h i s o pe ra t ion i sf a i r ly s imp le :

a l l t ha t i sr e -

q u i red i sf o r t wo r e f e rence p o in t s t o b e s e lec ted f r om t h e b a se map a nd t he i r g r id r e f e r e nce s i nt he r e qu i red c o -ord ina te s y s tem t o b e e s tab l i shed .

B y c o mpa r ing t h e t wo map

r e f e rence s w i th t h e i r c o r re spond ing t ab le t c o -o rd ina te s i ti st hen p o s s ib le t oc a lcu la te t he s c a l ing f a c to r s a nd t he d i ff e rence s i ng r id o r ig in s a nd g r id o r ien ta t ion n ece s sa ry t o c a l i b ra te t h e n ew ly d i g i t i sed p o in t s . Howeve r , i np rac t ice t h i s o pe ra t ion i sh i gh ly s u scep t ib le t o h uman e r ro r , a nd e ven t he s e em ing ly mo s t t r iv ia l o fm i s take s c an i n t roduce i n to le ra b l e l e ve l s o fi n accu racy i n to t he f i na l s y s tem d a ta .

C hap te r 2 : Mak ing t he Da ta A va i lab le

6 0

T he Ha rdwa re F o r t h i s p ro jec t t he c ho ice i n t h e h a rdwa re u sed w a s d e te rm ined b y t ha t a l ready a va i l a b le i nt he D epa r tmen t i nw h ich t h ew o rk w a s c a r r ied o u t . T h i s c on s i s ted o f aR e sea rch Mach ine s 3 80Z m ic rocompu te r a nd aB ITPAD ONE t ab le t d i g i t i se r . T he o n ly a va i lab le d r ive r p rog ram ( s ee b e low ) s uppo r ted b y t he s y s tem w a s a n i n -hou se p rog ram w r i t ten i n ALGOL 6 0 ( Ryan & Sm i th , 1 984 ) .

T he C onve r s ion P rog ram A l though t he o r ig ina l ALGOL 6 0 p rog ram w r i t ten b y R yan a nd Sm i th d i d c on ta in a r ou t ine t o c onve r t d i g i t i sed p o in t s i n to map r e f e rence s i tw a s n o t q u i te s u i tab le f o r t h i s p ro jec t . A c o mp le te ly n ew r ou t ine w a s t he ref o re w r i t ten t o c a r ry o u t t h i s o pe ra t ion . T h i s r ou t ine w a s d eve loped t h rough s e ve ra l p ro to type sw h ich , f o r o ne r ea son o ra no the r , p roved i n adequa te f o r t h e t a sk . T he e a r l ie s t v e r s ion s u sed t he f undamen ta l mode l o ft he t wo -po in t r e f e r ence p rocedu re o u t l ined a bove . A t f i r s t i tw a s b e l ieved t ha t t h i s w a s a n a dequa te m e thodo logy a nd s e ve ra l b a se map s w e re d i g i t i sed o n t h i s a s sump t ion . Un f o r tuna te ly , w hen i tc ame t or e con s t ruc t ing a d jacen t u n i t s a nd p lo t t ing t hem o u t , i tw a s d i scove red t ha t t h e d if e ren t s t re tche s o f b oundary d i d n o t a lway s ma tch p rope r ly . T he se a bo r t ive a t temp t s w e re d i sca rded . I tw a s r e a l i sed t oo l a te t ha t o n s eve ra l d if e ren t o cca s ion s i n co r rec t g r id r e f e rence s h ad b een a s s igned t o o ne o r more o ft he b a se p o in t s . When t he e no rm i ty o ft h e e r ror s b ecame a ppa ren t t he d i g i t i sa t ion p rocedu re w a s r ede s i gned t o i n c lude t he s e lec t ion o f at h i rd r e f e rence p o in t . T h i s i su sed t o c ro s s -check t he f i r s t t wo c o -o rd ina te s . A much mo re r e l iab le p rocedu re e mp loy s al oop w i th t h ree i t e ra t ion s . On e ach i t e ra t ion , t he u se r i sp romp ted t o k ey i nt he m ap c o -o rd ina te s o f ar e f e rence p o in t ( f rom t he b a se map ) a nd t hen t o ma rk t h e c o r re spond ing p o in t o n t h e t ab le t u s ing as t y lu s o r amou se w i th ac ros s -ha i r c u r so r . T he f i r s t t wo p o in t s a r e u sed t oc a lcu la te t he d if e rence s i nt he o r ien ta t ion , s c a le , a nd o r ig in b e tween t he t ab le t d i g i t i se r a nd c o -o rd ina te s y s tem o ft he map . T h i s a l low s a n a pp rop r ia te c heck t ob ea pp l ied . At e s tc an t hen b e made t oe n su re t ha t t he c o r rec t t r an sf o rm h a s b een c a lcu la ted . T he p rog ram t ake s t he b i tpad c o o rd ina te s o ft he t h i rd r e f e rence p o in t a nd a pp l ie s t he t r an sf o rm t o c a lcu la te t he e qu iv a l en t c o -o rd ina te s i nt he r equ i red m ap r e f e rence s y s tem . T he se a r e t hen c ompa red w i th t he m ap r e f e rence s t he u se r h a s e n te red f o r t he r e f e rence p o in t , a nd t he u se r i st o ld b y h ow much t he e xpec ted a nd t he c a lcu la ted v a lue s d i f f e r . T he u se r c an r e jec t t he t r an s f o rm , a nd r e se lec t t he r e f e r ence p o in t s , o r a ccep t i ta s a ccu ra te , a nd a l low t he p rog ram t o c onve r t t he d i g i t i sed b ounda ry p o in t s a nd w r i te t hem t o d i sk .

Ano the r n o tewo r thy

mod if i ca t ion t o t he o r ig ina l d i g i t i sa t ion p rog ram w a s m ade . T he s y s tem f o r p roce s s ing t h i s d a ta w a s d eve loped a nd i mp lemen ted o n a n I CL 2 966 ma inf ram e c ompu te r . B ef o re t he d i g i t i sed d a ta c ou ld b e e n te red i n to t he s y s tem t hey h ad f i r s t t o b e t r an sf e r red f r om t he RML 3 80Z t o t he I CL 2 966 .

T he s of twa re f o r c a r ry ing o u t t h i s o pe ra t ion a l ready

e x i s ted ( Ryan , 1 982 ) , b u t t h e t r an sf e r p rog ram w a s d e s igned t o s end o ne r e co rd a t a t ime . Due t o t h e p ro toco l r equ i red t o a l low t h e t wo m ach ine s t o c o mmun ica te t ype t r an sf e r t im e w a s a bou t t wo s e cond s p e r r e cord a t9 600 b aud . S i nce t he n umbe r o fc o o rd ina te r e co rd s b e ing t r an sf e r red w i l l b e l a rge , i tw a s a ppa ren t t ha t t h i sw ou ld b e av e ry t ime c on sum ing e xe rc i se .

H oweve r , i tw a s d i scove red t ha t t he max imum p e rm i t ted r e -

c o rd s i ze t ha t c ou ld b e t r an sm i t ted w a s 2 56 b y te s . S ince t he b a s ic map c o -o rd ina te c ons i s t s o f as i ng le d i g i t f l ag , p lu s t wo s i x f i gure c o -o rd ina te s ( i . e . 1 3b y te s ) , i ti sp o s s ib le t o c onca tena te 1 9 s uch l o g ica l r e co rd s i n to o ne p hy s ica l r e co rd ( i . e . 1 9x 13= 2 47 b y te s ) C hap te r 2 : Mak ing t h e Da ta A va i lab le

6 1

a nd t hen s end t he c o -o rd ina te s . f a c to r o fn ine teen .

T he t r an sf e r t ime s a r c c on sequen t ly s peeded u p b y a

Me rg ing Ad jacen t Map s T he p rocedu re f o r a dd ing n ew u n i t s t o t he s y s tem w a s d e sc r ibed i n " Reco rd ing a nd S to r ing aT heore t ica l L and -Sy s tem" o n p age 5 8 . T he p u rpo se o ft h e s y s tem i st oe nab le n ew u n i t s t o b e a dded t o t h e s y s tem i ns uch aw ay t ha t i ti sn o t n ece s sary t o r e -d ig i t i se ac ommon s egmen t o fb oundary t ha t h a s a l ready b een e n te red . T o d o t h i s t h e s y s tem r e l ie s o n t he f a c t t ha t t he u se r c an g i ve t he n ame o ft he u n i t a nd a f a i r ly a ccu ra te , b u t n o t n ece s sa r i ly e xac t , i n d ica t ion o ft he c o -o rd ina te s o fi n te r sec t ion p o in t s d e l im i t ing t he c ommon b oundary . T he b a se map s u sed i nt h i s p ro jec t ( i . e . t ho se i n Wood s ( 1 867 ) a nd C ubbon ( 1979 ) ) h ave ap a r t icu la r f e a tu re w h ich i si mpo r tan t w hen i tc o me s t oa dd ing u n i t s f r om ap a r i sh o n to a n a d jacen t o ne t ha t h a s a l ready b een f u l ly c ompu te r i sed . T he map s o ft he t r een s a nd q ua r te r land s a r e p ro jec ted o n ap a r i sh b a s i s . T he re i sn o o ve r lap b e tween t hem . T h i s m ean s t ha t t he i n te r sec t ion p o in t s o ft he u n i t s w h ich b o rde r o n to t h e p a r i sh p e r ime te r d o n o t a ppea r o n t he i r m ap s o ft he a d jacen t p a r i sh ( s ee F i gu re 2 8 o n p age 6 3 ) . T he e x i s t ing map s t hu s c au se m a jo r p rob lem s f o r c o mpu te r i s ing t h e d a ta f o r t h e w ho le a r ea . A s a l l t he se map s a r e p ro jec ted a t d if e ren t s c a le s a nd o r ien ta t ion s i tw ou ld n o t b e p o s s ib le t o t r an sc r ibe t h e se p o in t s a ccu ra te ly f r om o ne m ap t o t h e o the r m anua l ly . T he p rob lem i s o ve rcome b y d i g i t i s ing t ho se i n te r sec t ion p o in t s o n t he n ew p a r i sh b ounda ry a nd i n se r t ing t hem i n to t he l i s t o f» p o in t s a l ready i nt h e BOUNDER d ef in ing t he c on t iguou s p a r i sh b oundary . T he { TEXT } f i l e i su pda ted t o a ccommoda te t he c hange . T h i s s o lu t ion i sa t t rac t ive i nt ha t i to ve rcom e s as ub s tan t ia l p rob lem w i th n eg l i g ib le e f ec t o n t he r e s t o ft h e s y s tem .

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