TRANSFORMATION
CHAPTER 5: MATERIALS AND METHODS
5.1. GEOGRAPHICAL INFORMATION SYSTEM TECHNIQUES
Amend spatial extents of 1998CadastralGIS Database
Title deed search of 1944 properties.
,Ir Analysis of Grant outlines and diagrams
1944 LAND OWNERS HI MAP AND ASSOCIATED DATABASE
Database further amended with additional categories being added.
1999 LAND OWNERSHIP MAP AND ASSOCIATED DATABASE.
Calculate areas and perimeters of individual polygons and the sums of the various Land Categories, using'ArcView Version 3.0'.Where further detailed statistical analysis was required,'Quattro Pro Version 6.1' was used.
LANDOWNER INVOL VEMENT IN FUTURE PLANNING AND CATCHMENT MANAGEMENT Workshops and
Meetings Interviews using questionnaire
1944 AND 1999 LAND MANAGEMENT CHANGES Field verification of Land Categories and Laud Management.
Digitise delineated Land Categories from film overlays, using 'ArcView Version 3.0' GIS software and 'SummaSketch 1II'(active tablet area 304 x 305 mm) digitizing tablet.
Delineate Land Categories from 1944 and 1999 aerial photographs and mark onto
film overlays over orthophotographs.
Interpretation based on physiognomic classification system.
Calculate areas and perimeters of individual polygons and the sums of the various Land Categories, using 'ArcView Version 3.0'.Where further detailed statistical analysis was required, 'Quattro Pro Version 6.1' was used.
1944 AND 1999 LAND CATEGORY MAPS AND ASSOCIATED DATABASE
Figure 5.1. Steps to Determine Land Transformation and the Resulting End Products Provided 0\.p.
Where discrepancies such as variationin feature size and type and varying location were found, these were checked and where necessary corrected. Aerial photographs were interpreted according to a physiognomic-structural vegetation classification systemdeveloped by Granger (undated),whichwas based on a scheme proposed by Edwards (1983). Physiognomy is defined as, 'the appearance,especially the external appearance, of the vegetation, partly resulting from, but not to be confused with, structure and function...' (Fosberg 1967 in Edwards 1983).
Vegetation structureis defined as,'the organisation in space of the individuals that form a stand (and by extension a vegetation type or a plant association)' and the 'primary elements of structure are growth-form, stratification and coverage' (Danserau 1957 in Edwards 1983). Granger's classification system incorporates growth-form, stratification (height) and coverage (also known as projected canopy cover (FCC) and crown:gapratio) (Appendix 5.(p.140)).
Projected canopy cover of the upper stratum is defined as the vertical projection of the crown or shoot area of the plant onto the ground (Edwards 1983 in Granger undated).The amount of cover contributed by the canopy stratum can also be expressed as a ratio betweenthe mean diameter of the crown to the distance between crowns. This is termed crown:gap ratio (Edwards 1983 in Grangerundated).Granger's system comprises eight primary categories, 66 secondary categories and over 1000 possible 'real' categories at the tertiarylevel. The level of detail used is dependent on the requirements ofthe studyand on time constraints. Asthis study is intended to provide a database of selected features for future planning and catchment management, a large numberof categories were identified, with provision being made for these in the Geographical Information System (GIS) database. Thisis to allow flexibility for updating the database by catchment users and thus to ensure that the database remains dynamic over time. Due to time constraints and this dissertation being a course work Masters and not a full Masters dissertation, data for many of these categories has howevernot been inserted.For the purpose ofthis study data has predominantly been inserted to the primary category level. Other information has been added such as: habitat moisture regime for grassland and 'Exotic Vegetation -Wild';timber species for 'Exotic Vegetation - Managed' and degrees of erosion.
The eighth primary category, 'Exotic Vegetation' was omitted and three 'Exotic Vegetation' categories were added, namely:'Exotic Vegetation - Managed', 'Exotic Vegetation - Wild' and 'Exotic Vegetation - HumanHabitation'. Thiswas done to create a distinction between exotic vegetation,which was 'wilfully' planted and that, which has 'escaped' and invaded indigenous areas.
Other primary categories were added for land use types not termed indigenous vegetation.
These included: 'Cultivation - Commercial','Cultivation - Subsistence',rock outcrops, erosion, quarry, farm dam, buildings and main roads. Definitions of the physiognomic categories are contained in Appendix 5.(p.140).
Control points were marked onto each 1944 and 1996 film overlay, by dividing the orthophotograph map area into nine uniform squares. Control points were situated at the intersections and corners of the squares. Latitude and longitude were noted for each intersection and corner. These points were then translated into decimal degrees by dividing the minute value by 60 and multiplying by 100. The degree value remained unchanged.The division of 60 was used as there are 60 minutes in every degree. Alllongitudes (y) were given a negative value, due to being located in the southern hemisphere. Latitudes (x) were given a positive value.The annotated film overlays with marked control points were then secured separately onto the active tablet area of a digitising tablet ('SummaSketchIll',active tablet area - 304 x 304 mm) with masking tape. Using the GIS software package 'ArcView, Version 3.0' a 'project' file with two 'views', Land Categories 1944 and Land Categories 1999 were created.
View properties for each 'view' were set to:map units - decimal degrees and distance units - metres. No projection was set. This was so that data created could be projected to the required projection at a later stage.This was advantageous as it allows compatibility with other digital databases, attained from other sources with varying projections.Various 'theme' files and their corresponding 'attribute tables' with 'fields' were created for 1944 and 1999 (Table 5.1. (p. 49)). Prior to digitising, each annotated map was registered according to the geographic space in the 'view ' . This was achieved bytransferring the ground co-ordinates for the control points that were identified into the 'ArcView Version 3.0' GIS software. The digitiser setup from the 'view' menu was initiated, the digitizer puck icon was activated and the puck was used to click on four previously marked corner control points. The points were clicked in a clockwise direction. The x andydecimal degree values for each control point were entered.If error limits of 0.010 or less were achieved the map was registered.Digitising was undertaken in absolute (digitising) mode and commands of 'ArcView Version 3.0' were accessed by relative (mouse) mode.Digitising was undertaken on one digitising 'theme' for 1944 and 1999, respectively.
Table 5.1. Theme Files and Corresponding Attribute Table Fieldsfor Land Categories in 1944 and 1999
THEME ATTRrnUTETABLE-FlliLDS
Forest shape, id,code,area,perimeter
Thicket shape,id,code,area,perimeter
Shrubland shape,id,code,habitat moisture regime, under storeycode,area,perimeter
Woodland shape, id,code,habitat moistureregime, under storeycode,area,perimeter
Grassland shape, id, code,species, habitat moisture regime,managed, area,perimeter Herbland shape, id, code,under storeycode,area,
perimeter
Forbland shape,id,code,area, perimeter
ExoticVegetation - Managed shape,id,code, species,status,area,perimeter ExoticVegetation - Wild shape,id, code,species,status,habitat moisture
regime,area,perimeter
ExoticVegetation - Human Habitation shape, id, code,area,perimeter
Cultivation - Commercial shape, id,code,crop type, status,area,perimeter Cultivation -Subsistence shape,id, code,crop type, status,area, perimeter Rock Outcrops shape, id, code,area,perimeter
Erosion shape,id, code,area,perimeter
Quarry shape, id,area,perimeter
FarmDam shape,id,area,perimeter
Buildings shape, id, code,area,perimeter
MainRoads shape, id, area,perimeter
Large entire areas with multiple land category features within were digitised. Individual land categories were then 'cut' and 'pasted' onto their own 'themes' offorest, grassland etc.This method ensured digitised features occurred exactly adjacent to one another with no gaps in between. Areas, perimeters and properties of individual polygons for each land category of forest, grassland etc. were calculated after the field verification, as described in 5.2. and questionnaires and interviews, as described in 5.4 below had been completed. Areas and perimeters were calculated via running an 'ArcView - Avenue' script called 'calcapl.ave'. The script worked only when the 'theme' was active, the 'attribute table' of the 'theme' was open, the 'field' 'area' was selected and when the 'view ' had been projected. The land category features were initially digitised with the map units - decimal degrees and distance units - metres.
The Surveyor-General 1998 property cadastral database used was also supplied with the map units - decimal degrees and distance units - metres.The area and perimeter calculation worked only when the 'view' properties were altered to:Projection - Transverse Mercator; Spheroid - Clarke 1880 and Central Meridian - 310East. The projection type was chosen asitwas the same as that of the Orthophotographs (Gauss Conform Projection) from which the land categories were digitised. 'ArcView Version 3.0' does not support the Spheroid - WGS84, which is now widely used.Areas and perimeters calculated were therefore not compliant with this spheroid type. However, as the land category maps were digitised and the Surveyor- General 1998 property cadastral database was supplied with the map units - decimal degrees and distance units - metres, with no projection or spheroid specified, by using 'ArcView Version 3.2.'these maps could be projected to this spheroid and areas and perimeters may be calculated according to this spheroid type, should this be required. Total areas of all polygons in each land category and for all properties of 1944 and 1999 were attained by using the 'attribute table' function, 'statistics' from the field menu. For the 'statistics' function to work, the 'field' area had to be highlighted and numerated.Area statistics attained other than total area included:numbers of polygons, mean area, maximum area and minimum area of polygons, range,variance and standard deviation of data. Where land categories had been separated into other categories such as:habitat moisture regime, timber species and degrees of erosion, these were simply totalled.Where further statistical analysis was required 'Quattro Pro Version 6.1.' was used for manipulation and analysis.
Various GIS digital data sets were obtained from Government bodies, organisations and from individuals. These were obtained to provide background descriptive information on the study area andto provide a base on which to build new information. A list containing information such as:database name, description, method and scale of capture, date of capture, source of data / acknowledgement and usage in this dissertation is included as Appendix 6(p.141).
5.2. FIELD VERIFICATION OF LAND CATEGORIES AND LAND MANAGEMENT