Proceedings of the 21st International Cartographic Conference (ICC) Durban, South Africa, 10 � 16 August 2003�Cartographic Renaissance� Hosted by The International Cartographic Association (ICA)ISBN: 0-958-46093-0 Produced by: Document Transformation Technologies

THE DEVELOPMENT OF THE SOUTH AFRICAN NATIONALTOPOGRAPHIC INFORMATION SYSTEM

Vorster, P.J.

Chief Directorate: Surveys and Mapping, Department of Land Affairs, Private Bag X10, Mowbray, South Africa.E-mail: pvorster@sli.wcape.gov.za, Website: http://w3sli.wcape.gov.za/

ABSTRACT

The Chief Directorate: Surveys and Mapping (CDSM) is South Africa�s National Mapping Agency and is mandated,amongst others, to provide and maintain national mapping coverage of the Republic. The primary national mappingseries is the 1:50 000 series, consisting of 1912 map sheets, each covering a ¼ by a ¼ degree square (approximately25km by 25km). It is this mapping series that was to eventually form the basis for the National TopographicInformation System (NTIS).

The primary development of the NTIS spans a period of 11 years, commencing in 1986 and being completed in 1997.In developing the NTIS the CDSM would implement two distinct processes, the first being a scanning and vectorisingprocess, and the second being a GIS population and structuring process. The Geographic Information System (GIS),acquired in June 1988, was a locally developed package, named ReGIS, running on an AOS/VS platform. UNIX, OS/2,Windows 3.1 and then Windows NT would later replace the AOS/VS operating system. Intergraph�s GeoMediaProfessional 3.0 would replace the ReGIS GIS in 1999.

The paper will provide a chronological overview of the two stages of development of the NTIS. The first stage was apilot project, where the 1:500,000 national map series features were scanned, vectorised and populated in a GIS toprovide a completed sample database for evaluation purposes. The second stage would build on the strategy andprocess refinements of the pilot in order to establish the NTIS through the scanning, vectorising and GIS population ofthe major features of the 1:50 000 mapping series. A brief description of the difficulties encountered, and the effects ofthese on the datasets produced, will be incorporated.

An overview of the various digital processes that have been put in place to upgrade the data, which is cartographic innature, to that of a topographic dataset will be presented. Here the process environments, and the relevant systems andtechnologies in use, will be identified. The NTIS primary data classification will be listed.

Examples of NTIS application, where this database has proven itself to be a valuable national asset, will be highlighted.The conclusion will then summarise proposed future developments that will affect the NTIS.

1. INTRODUCTION

The Chief Directorate: Surveys and Mapping (CDSM), South Africa�s National Mapping Agency, is responsible for theprovision and maintenance of national topographic map products, an orthophoto mapping series, national controlsurvey networks and a national imagery database. The national topographic line map products are produced at scales of1:50,000, 1:250,000 and 1:500,000. The orthophoto map series is produced at 1:10,000 scale and covers metropolitanand national development areas. The control survey networks comprise national three-dimensional and verticalnetworks. The three-dimensional networks comprise a trigonometric network, consisting of approximately 30,000beacons, an active GPS base station network, named TrigNet (1), currently consisting of 34 base stations, and townsurvey mark schemes, present in more than 120 towns and cities throughout South Africa. The vertical networkcomprises a national precise levelling network, consisting of approximately 20,000 benchmarks. The national imagerydatabase currently consists of aerial photography dating back to 1936.

The CDSM provides additional cartographic map products, at various scales, of each of the 9 provinces of SouthAfrica, South Africa, Southern Africa and Africa (south of the Sahara). The International Civil Aviation Organisationmaps, covering Southern Africa, at scales of 1:500,000 and 1:1000,000, are produced and maintained by the CDSM onbehalf of the Civil Aviation Authority. The CDSM also maintains a topographic names database, affiliated to the South

African Geographical Names Council (SAGNC) and provides in-house training to students studying in the fields ofSurveying, Cartography and Geographic Information Systems.

It is important to note, from an organisational point of view, that up until 1997, the functions and responsibilities of theCDSM were incorporated within the Chief Directorate: Surveys and Land Information (CDSLI). The CDSLI wouldalso be entrusted with the management of the cadastre via four satellite Surveyors� General Offices. The developmentof the NTIS would, therefore, be one of three Information Systems initiated by the CDSLI. The other two databasesbeing the Cadastral Information System (CIS), a GIS of all cadastral land parcels, and the State Land InformationSystem (SLIS), a GIS of all state owned land parcels. These three databases would collectively be referred to as theNational Land-Oriented Information System (NLOIS). In 1997 the CDSLI would be re-engineered resulting in thecreation of the Chief Directorate: Cadastral Surveys (CDCS), entrusted with the management of the cadastre, and theCDSM. For the sake of simplicity I have referred to the CDSM and the CDCS and not the CDSLI.

The primary national mapping series is the 1:50 000 series, consisting of 1912 map sheets, each covering a ¼ by a ¼degree square (approximately 25km by 25km). Technological developments in the fields of digital photogrammetry,mapping and GIS prompted the CDSM to replace its manual mapping methods with their digital counterparts. To thisend it was decided to develop a national topographic database, based on the national 1:50,000 topographic map seriesproduct, to become the National Topographic Information System (NTIS).

The development of the NTIS would entail two distinct processes, the first being a scanning and vectorising process,and the second being a GIS population and structuring process. The NTIS development programme, spanning 11 years,commenced in 1986 with the acquisition of a scanning and raster to vector digital conversion system. The first stage ofdevelopment was a pilot project, consisting of the digital conversion of the 1:500,000 national map series, allowing theCDSM to refine processes and strategies prior to commencement of the second stage. The GIS data capture wouldcommence in 1988 with the acquisition of the first GIS system, named ReGIS. The pilot project would be completed in1992 and would serve as a prototype for the eventual NTIS. Maintenance of this pilot 1:500,000 database would ceasein 1996. The second stage of development consisted of the creation of the NTIS proper, consisting of the raster tovector conversion of the 1:50,000 national map series. The second stage would overlap the first stage where this stage�sraster to vector conversion process would commence in 1988 with the GIS population and structuring commencing in1992 and being completed in 1997.

Post 1997 has seen continued maintenance of the system where newly compiled topographically captured data hasreplaced the initial data captured, which is cartographic in nature. Various feature types, omitted in the initial capture,have been captured and general maintenance and partial clean-up procedures have been implemented.

The current focus is threefold, firstly, to implement error detection and correction processes to ensure a topologicallycorrect relief and hydrological national dataset, secondly, to define a CDSM data model, incorporating all omitteddatasets, where this data model will be implemented and populated accordingly and, thirdly, to continuously replace theNTIS cartographic source content with newly acquired topographically sourced data.

2. STAGE 1: THE DIGITAL CONVERSION OF THE 1:500,000 MAP SERIES PILOT

The first stage would consist of the digital conversion of the 1:500,000 map series. Here, for each map sheet, therelevant map separate film positives would be scanned and the raster points, lines and polygons converted to theirvector equivalent as a first process. The second process would entail the GIS population and structuring of the datawithin the defined classification schema. The 1:500,000 map series contains 23 map sheets, Figure 1, where the basecartographic material of each sheet consists of five film separates being the black, blue, brown, red and green plates.

Figure 1. 1:500,000 Map series index.

2.1 Scanning and VectorisingThe first stage of the development of the NTIS commenced in July 1986 with the implementation of a SCITEX(Scientific Textiles) system, running on a proprietary operating system. The system configuration is set out in Table 1.

Table 1. SCITEX system configuration.

Component Units Sub-ComponentsScitex Scanner 1Scitex Super Plotter 1Scitex Response R-280(HP 1000 computers-32Kb RAM)

3 2 x graphic workstation1 x processing workstation

The Scitex Scanner would be used to scan the cartographic film separate positives and the Scitex workstations, in turn,would vectorise the line work contained within the scanned raster images and encode these for later import into theGIS. The Scitex workstations would serve a dual role in that revised edition cartographic film separates would be editedand prepared for plotting to the Scitex Super Plotter for use in the printing of new edition maps.

Production shifts were introduced in 1987 in order to maximise the raster to vector production programme. Two shifts,of two persons each, would realise 14 hour production days. The five cartographic film separates scanned, vectorisedand encoded were:! The Black plate: roads, power lines, railways, spot heights, built-up areas, etc.;! The Brown plate: Contours;! The Blue plate: hydrological features (rivers, pans, dams, pipelines, furrows, aqueducts etc.);! The Red plate: roads etc.;! The Green plate: Land use features (cultivated land, conservation areas, recreation areas etc.);

The process entailed:! Creating film positives for each of the film separates via manual reprographic processes;! Scanning film positives (@20 lines per mm (50µm) @ 77 minutes per scan [drum speed 300 revs. per min.]);! The registration, referencing and vectorisation of the black plate;! For subsequent scanned plates, the registration to the black plate and the vectorisation of these;! Feature coding and limited edge matching of vector data;! Archiving of raster and resultant vector data.

The primary scanning, vectorisation and encoding process of the 1:500,000 map features would be completed in 1988,with some additional work continuing through to 1991.

2.2 GIS population and structuringIn 1988 the CDSM acquired GIS technology for the first time. The original technology plan, as set out in Table 2, wasto be phased in over a period of five years.

Table 2. GIS Technology Plan (1988).

Component Units Sub-ComponentsBase System 1 Host Computer (1440 MB disk storage)

1 Local area network (connectivity)Workstations 4 Raster edit workstations

11 Graphic workstations (for editing)6 Graphic workstations (for digitising and editing)

Terminals 1 Graphic query terminal12 Alphanumeric terminals

Peripherals 5 Colour screen copiers2 Printers

The CDSM took delivery of the first phase of the GIS system in July 1988. The components of this first phase arelisted, in Table 3, in order to emphasise the advances in computer technology in the last two decades.

The host would house the entire GIS database with each of the Graphic workstations downloading /uploading sheetcomponents of this dataset, via the 10 base 5 network, but effectively operating in a standalone environment. The GISsoftware was a locally developed package, named ReGIS. The operating system was AOS/VS. In 1989 the existing

graphic workstations (DS7500) had a RAM upgrade to 6Mb as the initial 4Mb configuration proved inadequate for dataprocessing requirements! An additional digitising and editing workstation was acquired in June 1989. This workstationwould be the first acquisition of a 386 microcomputer (6Mb RAM, 20Mhz CPU speed and 150Mb HDD), running on aDisk Operating System platform (DOS), an A1 GTCO digitiser and the ReGIS software.

Table 3. GIS Implementation first phase.

Component Units Sub-Components DescriptionBase System 1 Host Computer MV 15000 (3 magnetic tape units, 8Mb RAM,

592 Mb HDD and ReGIS file server software)1 Local area network (connectivity) Supplied (10 Mbaud)

Workstations 2 Raster edit workstations The Scitex HP 1000�s were already in service.1 Graphic workstations (edit) DS 7500 (4Mb RAM, 160Mb HDD, 737Kb

floppy, 21Mb cassette and ReGIS software)1 Graphic workstations (digitise/edit) DS 7500 (4Mb RAM, 160Mb HDD, 737Kb

floppy, 21Mb cassette and ReGIS software andCalcomp digitiser)

Terminals 1 Graphic query terminal Data General Dasher (D461)3 Alphanumeric terminals Data General Dasher (D215)

Peripherals 1 Colour screen copiers Plotmaster2 Printers 180 and 350 characters per second.

A second such system was purchased, early 1990. In 1991, an additional four editing workstations were acquired.These workstations would also be 386 microcomputers running on an OS/2 platform (8Mb RAM, 20Mhz CPU speedand 150Mb HDD). The OS/2 operating system was preferred to DOS as it provided multi-tasking capabilities withimproved networking capability, user-friendliness and performance. These workstations would allow the CDSM togradually retire the DS7500 workstations from the production environment.

The vectorised and encoded data was imported and geo-referenced within the GIS by means of a customized �ScitexImporter� utility. Here the data was structured with respect to the classification tree, topology was added to sharedsegments, as chains, and edge-matched. The database consisted of a project file per 1:500,000 map sheet.

The first stage of the development of the NTIS, being the 1:500,000 GIS database pilot, containing all the featureinstances of that map series, was completed in July 1992.

3. STAGE 2: THE DIGITAL CONVERSION OF THE 1:50,000 MAP SERIES

The second stage would consist of the digital conversion of the 1912 map sheets of the 1:50,000 map series, utilizingthe lessons learnt during the pilot first stage, in order to establish the NTIS itself. An initial test capture of a typical1:50,000 map sheet realized a total conversion and GIS structure period of 6 months, implying a period of 900 person-years (or in excess of 100 years with available resources) to establish the NTIS. Client requirements (primarily the StateDepartments of Water Affairs, Environmental Affairs, Development Aid and Geological Surveys) demanded that theconversion and GIS population of the NTIS be completed in a 5 to 7 year period.

To realize this goal a partial capture was adopted where only the major features would be converted and form the basisfor the NTIS. In contrast to the first stage, this stage would require that only the black, blue and brown plate mapseparate film positives be scanned where the resultant raster points, lines and polygons of selected features would beconverted to their vector equivalent as a first process. The second process would entail the GIS population andstructuring of this data within the defined classification schema.

3.1 Scanning and VectorisingIn 1988, on completion of the first stage, the SCITEX system commenced with the raster to vector conversion andencoding of the selected 1:50,000 map feature instances. The partial capture necessitated the scanning, vectorising andclassification of the listed features within the relevant three cartographic film separates as set out Table 4.

A Data General Aviion 410 server would replace the MV15000 host in 1992. The AOS/VS operating system would bediscontinued and RAM and disk storage increased. The Aviion 410 ran on a Unix (DG/UX) operating system, had16Mb RAM and 2Gb HDD. The Aviion 410 would, again, only be used as a data archive, with the GIS workstationsoperating in a standalone environment and networked to this server.

Table 4. Partial Capture feature list.

BLACK PLATERoads National freeway, National route, Arterial route, Main road, Secondary road, Other road, Street in

built-up area, Road under construction.Railway Standard railway, Narrow gauge railway, marshalling yard, old disused railway, service railway,

station, rail under construction.Tunnels Tunnel, Tunnel on National Freeway, Tunnel on National route, Tunnel on Arterial route, Tunnel

on Main road, Tunnel on Secondary road, Tunnel on Other road, Tunnel on Street in BUP, Tunnelon Standard railway, Tunnel on Narrow gauge railway.

Bridges Bridge, Bridge on National Freeway, Bridge on National route, Bridge on Arterial route, Bridge onMain road, Bridge on Secondary road, Bridge on Other road, Bridge on Street in BUP, Bridge onStandard railway, Bridge on Narrow gauge rail.

Other Power lines, Built-up-areas.BROWN PLATEContours Index contour, Intermediate contour, Index depression contour, Intermediate depression contour.Other Cliff (feathered contour), Eroded area, Terrace.BLUE PLATERivers Single perennial river, Single non-perennial river, Double perennial river, Double non-perennial

river, Single dry river, and Double dry river.Dams etc. Dam water line, Dam wall, Lagoon, Lake, Marsh, Vlei.Pans Very small non-perennial pan, Perennial pan, Dry pan.Other Aqueduct, Canal, Furrow, Pipeline, Siphon, Coastline.

The features not vectorised, classified and captured within the NTIS are listed in Table 5.

Table 5. Not captured feature list.

BLACK PLATELine work Building, Hut, Large Building, Ruin, Silo, Fence, Track/Footpath, Aerial Cableway, Conveyor

belt, Cutting, Embankment, Excavation, Digging, Mine dump, Slimes dam, Wall, Weir, Airstrip,Airport, Anti erosion wall, Stock pen, Stadium, Large Reservoir, Sewage works, Coastal rock.

Symbols Trigonometrical Beacon, Wreck, Wind pump, Cemetery, Cave, Spot height, Battlefield,Monument, Benchmark, Magnetic Station, Marine beacon, Communication tower.

GREEN PLATELine work Cultivated land, Saaidamme, Orchard, Vineyard, Woodland, Forest, Single tree, Row of trees,

Recreational ground, Golf course, Racecourse, Nature reserve boundary, Fire break.RED PLATESymbols Lighthouses, Marine Lights.BROWN PLATELine work Eroded area, Rocky outcrop, Sand area, Sand dune, Mud flat, Sand bank.BLUE PLATELine work Reservoir, Fountain, Hot spring, Water tower, Waterfall, Rapid, Cataract, Salt works.

An analysis of Scitex production, from 1988 to 1990, revealed that a digital raster to vector conversion rate ofapproximately 120 map sheets per year could be maintained, requiring an estimated 15 year program to complete theconversion of the 1:50,000 map series. The system, as stated previously, would also be required to producecartographic map separates for the printing of new edition map sheets, extending this estimate. The CDSM acquired aLaserscan VTRAK system, in January 1992, to complement the Scitex system and ensure completion within the 5 to 7year window. The VTRAK system came into full production in July 1992. It would be the first true client server systemintroduced at the CDSM. The VTRAK system configuration is set out in Table 6.

Table 6. VTRAK system configuration.

Component Units DescriptionMaster Node 1 VAX Server 4000 (20Mb RAM, 600Mb HDD, 296 Mb

streamer tape, (1/2 � 1660BPI) tape drive)VTRAK Workstation 4 VAX Station 3100 (20Mb RAM, 665Mb HDD)

Figure 2. 16 sheets per Deg.Sq.

The VTRAK system had a proprietary VAX/VMS operating system and could vectorise in excess of 250 map sheetsper annum, with two shifts operating. A customised internal file format (IFF) converter would be created in order totransfer the VTRAK vectorised data to the ReGIS system. The VTRAK system would primarily be utilised for theraster to vector conversion and encoding of the blue and brown plate features, and the Scitex system would, similarly,convert and encode the black plate features.

3.2 GIS population and structuringThe GIS population and structuring of the 1:500,000 pilot database was completed in 1992. The NTIS, consisting of aGIS database containing a subset of the 1:50,000 cartographic map features would commence soon after. The long-termgoal was to attain countrywide coverage where the 1912 sheets would be edge-matched into a seamless topographic(cartographic) dataset. This would allow the creation of user defined map sheets that did not necessarily have to followthe boundaries of the hardcopy 1:50,000 map series and where multiple map sheet coverages could be combined into asingle map. An example application would be the Gauteng (Johannesburg/Pretoria) metropolis, which is containedwithin four separate 1:50,000 map sheets. Hardware and software capability did not support this ideal and the NTISwould initially consist of a database file per map sheet.

In January 1993 the 8 existing ReGIS workstations were upgraded and an additional 6 workstations were purchased.The 14 ReGIS workstations would run on a Windows 3.1 operating system with the accompanying compatible ReGIS(version 4.4) software purchase/upgrade. The ReGIS software utilized a proprietary database for spatial informationwhere attribute data was stored within a DBASE III database. During 1993 and 1994 the entire ReGIS workstationhardware fleet would be upgraded to 486 microcomputers (8Mb RAM, 33Mhz CPU speed, 200Mb HDD, 16 bitarchitecture).

In May 1993 the DG Aviion 410 NTIS server host was replaced by a DG Aviion 5500, (33 Mhz 88100 RISCprocessor, 32Mb RAM, 6Gb HDD), in order to increase disk storage capacity and improve database accessibility. Theserver would, however, continue to act as a data repository serving the ReGIS workstations. The local areanetwork(LAN) had been upgraded to 10baseT at this time.

In 1994 the Scitex Super Scanner (and Plotter) experienced increased maintenance problems, resulting in significantdowntime. To alleviate this problem an Intergraph Mapsetter 5000 plotter/scanner was purchased and put into operationin January 1995. The Mapsetter 5000 specifications are set out in Table 7.

Table 7. Mapsetter 5000 Production Specifications.

Operation Production SpecificationsScanning Resolution: 12.5µm (±5 µm)

Speed: 2 megapixels per second (80 min.)Plotting Resolution: 12.5µm

Speed: 8 megapixels per second (20 min.)

The Mapsetter 5000 would be commissioned at a 20 µm scanning resolution resulting in an average period of 45minutes per map separate scanned, realising a 40% gain in production time (at double the resolution) when compared tothe Scitex Scanner.

In 1996 the 14 workstations would be upgraded to Pentium microcomputers operating on the Windows NT operatingsystem (32Mb RAM, 120MHz CPU speed, 1Gb HDD, 32 bit architecture) in order to support the ReGIS softwareupgrade to this platform.

These hardware developments allowed the creation of multi-sheet,edge-matched databases for the first time. Each map sheet requiredapproximately 40Mb HDD storage. The adjacent four files would bemerged and edged-matched to form a ¼ degree square block (160MbHDD storage) and then adjacent blocks would be edge-matched(320Mb HDD storage) until a full degree square was completed,Figure 2.

3.3 �Project Rapid Update�In 1996 the CDSM was approached by the Central Statistical Services(CSS) (later to be re-named Statistics South Africa) to provide digitaltopographic base data for South Africa. The CSS wished to integrate

this data with the Chief Directorate: Cadastral Surveys� (CDCS) Cadastral Information System (CIS) in order togenerate a geo-spatial database of enumerator areas relating to the 1996 census. The CSS 1996 census data wascaptured by means of alphanumeric text descriptions accompanied by sketch plans (2). The Independent ElectoralCommission (IEC) would then use the enumerator dataset in order to determine Voting Districts to be used in the 1999elections. The Municipal Demarcations Board (MDP), constituted in 1998 (3), would then determine municipal andother boundaries from these voting districts, Figure 3.

Figure 3. IEC and Census data capture.

The cadastral database would be the primary source for the determination of enumerator areas in formal urban areas.The enumeration of rural areas, however, utilized both cadastral and topographic features as boundaries and thisrequired the NTIS database to spatially reference these enumerator areas. An assessment of the progress made in thedevelopment of the NTIS database, table 8, revealed that approximately 1000 of the 1912 1:50,000 map sheets wouldhave to be captured in order to adequately support the CSS.

A project named �Rapid Capture� was formulated at the CDSM, where the NTIS database would be sufficientlycompleted to serve as reference for the enumerator area determination. This project would commence in June 1996 andbe completed in June 1997.

The project would entail (refer Tables 4 and 8):! Black Plate: The capture of road features only, where the built-up-areas and power lines were excluded;! Blue Plate: these features would be captured, but area features narrower than 750m (i.e. Pans) would be excluded;! Brown Plate: the capture of these features received low priority;! Topology: shared segments would not be structured and edge matching received low priority.

Table 8. Progress from 1989 to 1995 (To do: �Rapid Capture�).

Early in 1996, the Scitex Scanner (after eight years of service) broke down and was removed from the production line.The Mapsetter 5000 could not provide all the necessary scanning required for the �Rapid Capture� project, and aContex scanner (optical resolution 300dpi / interpolated resolution 600dpi) was sourced, on loan, to fill the void. TheContex scanner would provide a scanning resolution of 600dpi(~43µm) and a production rate of 10 minutes perscanned film map separate. Project �Rapid Capture� would be completed in July 1997. In parallel, the CDCS wouldrapidly complete the population of its CIS through �Project Hope� (to complete the country-wide capture of ruralcadastre) and �Project Miracle� (to complete the capture of urban cadastre).

3.4 �Project Merge� In June 1997, the CDSM embarked on �Project Merge� to assist the CSS in creating a GIS of enumerator areas. Thetarget date was 31 December 1997. In May 1997 a DG Aviion 3600 NT server (24Gb raid capacity) was acquired andReGIS (Gserver) management software loaded allowing for the creation of �Multi-User Geobases�(MUG�s). Thisconfiguration would provide client server functionality and introduce quad tree indexing, allowing the creation acountrywide seamless NTIS for the first time.

Within �Project Merge� the CDSM would combine, structure and edge match the relevant degree square topographicdatabases referenced to 1:500,000 map sheet areas, Figure 1, thereafter these databases would be combined structuredand edge matched within the four MUG�s (NW, SW, NE and SE), Figure 4. To avert data volume and operationaldifficulties a single countrywide database was not contemplated.

Figure 4. The four MUGS.

The CDSM would then successfully merge and vertically integrate the rural topographic and cadastral datasets and thenderive the ±6500 (of the ±86000 total) enumerator area polygons.

In addition, the CDSM produced digital colour orthophotos covering the informal housing areas in major urban areas,to be used in the field, by CSS contract staff, to identify and delineate the boundaries of those enumerator areas. TheCSS would experience difficulties in completing the latter and the CDSM would assist by carrying out the fieldidentification and delineation of ±3000 enumerator areas in the Eastern Cape rural, and the Cape Town and Gautenginformal housing areas. �Project Merge� was completed in the first quarter of 1998. Lester (4) provides an excellentsummary of the establishment of the CSS enumerator database and its successful application in support of the 1999South African national general elections.

Post �Project Merge� the CDSM resumed the capture of contours and correction of the NTIS content through errordetection and correction techniques.

3.5 The New South African Datum: Hartebeesthoek94 and transfer to an Oracle Spatial platformConcurrent to the development of the NTIS, the CDSM was in the process of re-defining the South African horizontalgeodetic datum, to be referenced to the WGS84 ellipsoid, by complete re-computation of this geodetic network. Thisnew datum, to be named the Hartebeesthoek94 Datum, would officially be adopted on the 1st of January 1999 (5). TheNTIS would require a datum transformation, from the Cape Datum (referenced to the modified Clarke 1880 ellipsoid)to this new datum. To complicate matters, AutoDesk acquired the ReGIS software source code, in 1995, with theintention to re-engineer the code from a 16 bit to a 32 bit application, redesign user interfaces, implement a new datastructure and rename it �Autodesk World�. �Autodesk World� would not support MUG�s. The ReGIS product was notWGS84 enabled and would not receive any further development. The CDSM had not only created the NTIS on theReGIS application suite, but had also integrated its photogrammetric data capture processes to it through customisedsoftware routines. Adopting the �Autodesk World� product would require the re-development of these customisedsoftware routines.

In March 1999 the CDSM replaced the ReGIS GIS application software with Intergraph GeoMedia Professional 3.0,which would manage the NTIS on an Oracle Spatial (relational-8i) database platform. Here the NTIS data was exportedin ReGIS feature file format where these feature files were then subjected to a datum transformation from the Cape tothe Hartebeesthoek94 Datum, Table 9.

Table 9. Datum Transformation Summary.

The transformed feature files were then imported and structured within the Oracle Spatial database where these datawhere indexed to the Hartebeesthoek94 map sheet boundary references. The migration to the new system wascompleted in October 1999, with final acceptance taking place in February 2000.

The advantages of the new system where/are:! A single centralised database on an Oracle Spatial platform;! Feature data validation tools;! Dynamic point snapping;! Improved graphic user interface (GUI) and image management;! Open system with extended input/output utilities to other data formats;! A refined hierarchical classification schema with 27 feature types and 233 related attribute types (Table 10).

Table 10. Features and number of related attributes.

The customised ReGIS photogrammetric data capture software would be replaced by uSmart photogrammetric datacapture software, running on a Microstation CAD platform. Intergraph�s Modular GIS Environment software (MGE)would serve to facilitate data transfer to the NTIS Oracle Spatial database.

In April 1999 the vectorisation of the remaining features, excluded from the �Rapid Capture� project (built-up-areas,power lines and contours), would be completed. The Scitex workstations would be decommissioned soon after. TheMapsetter 5000 was decommissioned in 2000. A Contex FSS 12300 scanner (optical resolution 400dpi / interpolatedresolution 800 dpi) would be acquired in 2000 to fulfil scanning requirements.

The VTRAK system would commence with the vectorisation of the 1:10,000 orthophoto contours in May 1999, until itwas decommissioned in November 2001. Two Intergraph IGeovec workstations would be acquired in 2001 to continuewith this work. The spot height data capture, from the 1:50,000 map series, commenced in 2000 and was completed in2001. The NTIS has been updated with 130 (81,250 km2) cartographically captured map sheets where all NTIS featureshave been captured.

The core component, responsible for the maintenance of the NTIS, currently consists of 16 GeoMedia Professionalworkstations (13 for data maintenance; 3 for data management, checking and plotting), 2 IGeovec workstations(vectorisation of 1:10,000 contours and other miscellaneous tasks) and 3 DEM Workstations (Digital Elevation Models(DEM) computation).

4. CURRENT TOPOGRAPHIC DATA CAPTURE SYSTEMS AND PROCESSES UPDATING THE NTIS

The CDSM introduced complete digital topographic data capture processes and techniques into its productionenvironments in 1996 with the first map sheet, 3030 CA St. Faiths, commencing capture on the 29th of April 1996. AllNTIS features per map sheet, excluding relief, are topographically captured for population in the NTIS. To date 430(270,000 km2) 1:50,000 map sheet areas have been compiled where 220 (137,500 km2) have replaced the originalcartographic data in the NTIS. A brief overview of these systems and processes, and the technologies used, will bepresented here.

A simple process flow diagram of the current topographic data capture process is presented in Figure 5.

Figure 5. Production Process.

The reader will notice tentative workflow process pointers within the scanning and rectification environments. Thescanning of aerial photograph film negatives is required for use in the digital photogrammetric workstation(DPW)/digital softcopy environment, and the rectification of these images are required where they will serve as sourcedata for monoplotter workstations. Alternatively, hardcopy diapositives are utilized for stereoplotter (analytical andanalogue) workstations. Careful management of the data capture workflow is carried out to ensure that all availableresources are utilized efficiently.

Aerial photography is captured on an annual basis covering 25% of the country in order to update the National Imagerydatabase and to serve as source for topographic data capture using photogrammetric techniques. Approximately 120sheets (75,000 km2) of the 1:50,000 topographic map series are updated annually.

The CDSM maintains a place and topographic names database. This database contains names that have been approvedby the South African Geographical Names Council (SAGNC). The database was digitally converted, and spatiallyreferenced, in 1998, and has served as source for the publication of Provincial Geographical Names Gazetteers for eachof the nine provinces, in 2001.

The National Digital Elevation Model (NDEM) database was re-designed in 2001 in order to reference it to the newSouth African Datum, Hartebeesthoek94, and to remove errors, deficiencies and data overlap. The previous databasewas not consistent (photogrammetrically captured from 1:150,000 photography, causing rifts at model edges),contained duplicated data (the 200m/400m DEM datasets had two degree overlaps within the South African projectionsystem) and had sparse coverage in rural areas (at 200m/400m intervals). The new database will be populated within an

Oracle database and will cover South Africa at a 25m interval. The elevation accuracy of the DEM will be ±2.5m (inareas derived from mass elevation data capture) and ±10m (in areas derived from 1:50,000 20m contour and spot heightdata).

The various production systems utilized within the CDSM data capture environments are listed in Table 11. The CDSMis progressively phasing out its analogue stereoplotter workstations and replacing these with digital photogrammetricworkstations. Analytical stereoplotter workstations will remain for the foreseeable future until such time thatcomparable image quality can be obtained within the digital environment.

Table 11. CDSM Production Systems

5. NTIS: SUCCESS STORIES

The NTIS has been successfully utilized in a variety of applications and projects. I wish to highlight the mostsignificant of these to demonstrate its usefulness and justify its creation.

These are:! In 1995 the pilot (1:500,000) dataset was utilized as data source for the creation of maps for the publication of the

Readers Digest Atlas of Southern Africa.! In 1997/8 the NTIS database served as reference for the determination of rural enumerator areas, in order to

determine voting districts, culminating in the successful South African general election held in 1999.! The NTIS has, and is serving as base spatial reference for the development of the South African National Land

Cover project 2000.! The South African component of the Global Map project, supplied in 2001/2, was sourced from the NTIS dataset

and restructured to Global Map specifications.! The CDSM, in 2002, completed the digital conversion of Swaziland�s entire 1:50,000 topographic map series,

consisting of 23 map sheets, where the same procedures and processes, used to create the NTIS, were applied.

6. NTIS CONTENT: PROBLEMS AND SOLUTIONS

The creation of the NTIS database required the capture of topographic feature entities within an area of 1,22 millionkm2, at an accuracy of approximately 20 metres. Difficulties have arisen and these have been addressed within theconstraints that existed at that time. Decisions made, inaccurate processes, technologies and other factors have led toerroneous and incomplete datasets within the NTIS.

No. EQUIPMENT PRIMARY SOFTWARE TASK/S

2 PUG point transfer devices Transfer tie points on diapositives1 BC2 stereoplotter Orima Aerial Triangulation1 Z/I Imagestation Z3 ISDM and ASAE Aerial Triangulation and Mass Elevation Data*2 Z/I Imagestation SSK ISAT Automated Aerial Triangulation*1 A/T Adjustment Workstation PAT-B Block Adjustment with GPS airstations*

4 AG1 stereoplotter uSmart (Analogue) Topographic Data Capture3 PG2 stereoplotter uSmart (Analogue) Topographic Data Capture2 A8 stereoplotter uSmart (Analogue) Topographic Data Capture1 Quasco PG2 stereoplotter uSmart (Analytical) Topographic Data Capture1 BC3 stereoplotter uSmart (Analytical) Topographic Data Capture7 uSMART Softcopy uSmart (Softcopy) Orthophoto Data Capture*

12 Monoplotter Workstations Geomedia Professional 5 Topographic Data Capture

16 NTIS Workstations Geomedia Professional 5 NTIS Data maintenance and structuring2 Vectorising Workstations Igeovec Raster to vector conversion (contours etc.)3 DEM Workstations 2xSCOP, Geomedia GRID Generate 25m DEM from mass elevation data and contours

1 Vexcel 4000 Scanner Vexcel proprietary Photogrammetric scanning of film negatives*2 Rectification Workstations ERDAS Imagine 8.6 Rectification of scanned imagery using DEM*

5 Orthophoto Workstations ArcView 3.2 Create Orthophoto Map Products

19 Cartographic Workstations LAMPS Create Topographic Map Products**

Aerial Triangulation Environment

* utilized in both the orthophoto and topographic data process workflows/** utilized for all scales of topographic map products

Compilation Environment

Scanning & Rectification Environment

Orthophoto Mapping Environment

Cartographic Mapping Environment

Database Maintenance Environment

I will highlight each of these and state how the CDSM has decided to deal with theme:! Incomplete feature content: In 1992 the CDSM made the decision to capture only the major communication, relief

and hydrological features to complete the development of the NTIS within a 5 to 7 year period. The �RapidCapture� project would omit further features in order to attain higher production rates to realise completion in 5years and assist in �Project Merge�;

! Limited metadata content: The NTIS is primarily a cartographic database, captured from scanned cartographic filmseparates, and, therefore, suitable and sufficient metadata was not available or was not captured;

! Positional errors in feature content: The commissioning of the Contex scanner, during the �Rapid Capture�project, would introduce positional errors within the NTIS dataset. This Contex scanner had inadequate rollers withwhich to secure the cartographic film separates during the scanning process creating distorted raster images;registration ticks were affixed to the film with wax resulting in movement of these during the scanning process andcausing registration inaccuracies (these would later be covered with tape to secure them). At a later stage theregistration ticks were scribed onto the film material, thus alleviating this error;

! Minimal topological content: The NTIS is effectively a spaghetti dataset that has been edge-matched and whereshared segments have been aligned, but are duplicated within the component entities;

The CDSM has embarked on a �Clean-up� project in order to correct the relief and hydrological components of NTIS.Errors and content deficiencies have and will be addressed, in the long term (approximately 10 years), through themaintenance program of the 1:50,000 national map series where new edition photogrammetrically captured mapfeatures will replace these erroneous features. Error detection and correction of manageable components will beaddressed as the need arises. The topological structuring of the NTIS will be addressed within a Data modelinvestigation where additional and omitted features will be identified for capture and the implications of introducing anobject model will be assessed and implemented.

7. CONCLUSION

The development of the NTIS has been successful and is justified through its use by clients on a daily basis. TheCDSM must now focus on the improvement of the database content and structure in order to ensure that it complieswith national and international standards and remains relevant to our clients. In this regard the CDSM has decided tofocus, in the short to medium term, on two areas of concern, firstly, to implement error detection and correctionprocedures and processes to ensure a topologically correct relief and hydrological national dataset and, secondly, to re-define the CDSM data model, incorporating all omitted datasets, where this data model will be implemented andpopulated accordingly.

A �clean-up� project, of the relief and hydrological datasets, commenced in April 2003 and will be completed inSeptember 2004. The result of this project will see these datasets being individually error free and logical in relation toeach other. The relief dataset will serve as raw data to complete the population of the 25m national NDEM, whereDEM, derived from mass elevation data capture produced via the orthophoto process, does not exist.

The CDSM data model investigation will commence in June 2003 and be completed in September 2003. Here aconceptual, logical and physical data model will be defined encompassing required and available disparate technicaldatasets. The Physical Model will serve as a guide in the creation, population and maintenance of an integrated CDSMcorporate technical data warehouse and will comply with relevant South African standards (SANS 1876: FeatureInstance Identification Standard, SANS 1878: South African Spatial Metadata Standard and SANS 1880: South AfricanGeospatial Data Dictionary (SAGDaD) and Its Application). The implementation of the Physical model will commencein October 2003.

8. ACKNOWLEDGEMENTS

I would like to express my sincere appreciation to my colleagues, Messrs. D Clarke, P Lucas, R Duesimi, R Swart andK Scott for sharing their knowledge and experience in the preparation of this paper.

9. REFERENCES

[1] Hedling G, Parker A, Wonnacott R, ION GPS 2000: 13th International Technical Meeting of the SatelliteDivision of the Institute of Navigation, TrigNet - The Network of Active GPS Base Stations for South Africa,(2000) http://www.ion.org/publications/toc/00gpstoc.html

[2] Statistics South Africa, Population Census, 1996, Chapter 2: Methodology used in Census �96, (1998)http://www.statssa.gov.za/RelatedInverseSites/census96/HTML/Metadata/Docs/count/chapter_2.htm

[3] Municipal Demarcation Board, South Africa, About Demarcation, Demarcating Metropolitan And DistrictMunicipality Boundaries, (1998) http://www.demarcation.org.za/Demarcation/about_demarc.html

[4] Lester K J, Cambridge Conference 1999, Shaping South Africa's Future with GIS - The 1999 General ElectionExperience (Paper 2.4), (1999) www.ordsvy.gov.uk/downloads/osi/paper2_4.pdf

[5] Vorster P J, The New South African (Hartebeesthoek94) Datum, South African Journal of Geo-Information, Vol.7, Part 6 160-170 (1998)

[6] CDSM technical files: ME 9/3 vol. 1, 5-9; ME 9/1 vol. 1-2; ME 9/4 vol. 1-2; PRE 2/2/1 vol. 1

THE DEVELOPMENT OF THE SOUTH AFRICAN NATIONALTOPOGRAPHIC INFORMATION SYSTEM

Vorster, P.J.

Chief Directorate: Surveys and Mapping, Department of Land Affairs, Private Bag X10, Mowbray, South Africa.E-mail: pvorster@sli.wcape.gov.za, Website: http://w3sli.wcape.gov.za/

Biography

The author received a B.Sc. Survey degree, from the University of Cape Town, in 1989.

He took up employment with the Armaments Corporation of South Africa (Armscor), at its Overberg Test Rangefacility, where he was responsible for the establishment of an extensive precise three-dimensional geodetic network,referenced exclusively to the World Geodetic System 1972 (WGS72) spheroid, to serve as the measurement frameworkfor the test facility�s real-time measurement technologies. Here he would be one of the first in South Africa to apply theGlobal Positioning System (GPS), as a geodetic measurement tool.

In 1992 he took employment with the Kwazulu government service in order to gain cadastral experience and tocomplete his articles towards attaining professional status. Here he would participate in large operations, utilizing GPStechnology, in order to delineate tribal authority boundaries. He completed his articles and was registered as aProfessional Land Surveyor in 1994.

In 1994 he would be employed with the Chief Directorate: Surveys and Mapping (CDSM), South Africa�s NationalMapping Agency (NMO). In 1995 he was promoted to the position of Deputy Director and would play an integral rolein the establishment of South Africa�s new South African Datum, based on the WGS84 spheroid, officially adopted in1999. He is currently responsible for the evaluation and application of current and new developments within thegeodetic, photogrammetric and related fields and technologies at the NMO. His management focus is within the field ofGeographic Information Systems (GIS) where he has been responsible for projects relating the maintenance of theNMO�s national topographic information system (NTIS) and the integration of national geospatial databases in thepublic domain.

He is currently in his final year of study for a B.Sc. (Honours) Geoinformatics degree, affiliated to the internationalUNIGIS programme.