Biocenosis • Vol 29(1-2)

reserve and the boundary is not easily determined on the ground.

3 Residential properties. Twenty three of the parks have residential properties adjacent to them. Four of these parks were entirely surrounded by residential properties with access to them gained by walkways.

4 Commercial properties. Two of the parks had commercial properties (shops) as a surrounding feature. In both cases the boundary between the park and the commercial property is clearly delineated. Both of these parks also had residential properties surrounding them.

5 Industrial areas. Seven of the parks had light to heavy industrial areas as a surrounding feature. In some cases the boundary between the park and the commercial property is clearly delineated.

5.2 Park Data

The data used in the experiments is digital image data of New Zealand specifically the Auckland area. Auckland Council governs the entire Auckland region in which there are over 4000 designated public parks and reserves to examine for possible en- croachment. The range in the parks’ sizes is substantial, for example in the Manukau area the parks range in size from 38 square meters to 1,995,880 square meters. From a land management viewpoint the parks were divided into four categories:

1 Parks that share boundaries with commercial and/or industrial properties. The surrounding features of a park and the length of shared boundaries may be important factors in the likelihood of encroachment occurring at a park. Commercial and industrial properties tend to be larger than residential prop- erties so the shared boundaries are usually longer. Teviot Reserve, on the North Shore, is an example of this type of park.

2 Parks that share boundaries with residential properties and are completely or almost completely isolated from features such as roads. The access to a park may be an important factor in the likelihood of encroachment occurring at a park. Isolated parks may not be visited frequently and this may encourage relatively small scale encroachment. Wyllie Park, in Manukau, is an example of this type of park.

3 Parks that share boundaries with residential properties, where the boundary is not clearly delineated physically on the ground. There are parks where there are no natural (e.g. hedges) or man-made (e.g. fences) physical boundaries

62 5. Land Encroachment in New Zealand

between the park and the residential properties. These parks may be more prone to encroachment. Diana reserve, on the North Shore, is an example of this type of park.

4 Parks that share boundaries with residential properties, where the boundary is obscured physically on the ground and/or from the air. There are parks where the boundary is difficult to access physically from the park side and where the boundary is obscured visually in aerial photographs by dense vege- tation. These parks may be more prone to encroachment due to the difficulties in being able to confirm the physical location of the boundary. Also, dense vegetation may obscure temporary encroachment such as garbage dumping and camping. Auburn Reserve, on the North Shore, is an example of this type of park.

The data sets used for the detection of encroachment are digital images of areas that include public parks.

1 Aerial Photographs. The aerial photographs are captured on-line. The scale is set manually to 7.5cm/234m at time of capture and the ratio is one pixel to 0.5 meters. The images are in JPEG format and were collected from Google Earth. 2 Geo-Referenced Aerial Photographs. The aerial photographs have a set scale of 7cm/20m and are in the New Zealand Transverse Mercator 2000 projection. The aerial photographs were downloaded as raster data in JPEG format and were collected from the Auckland Council via the GIS viewer (Auckland Coun-

cil, 2010). Figure 5.1 shows aerial photographs of four of the selected parks.

3 Land Boundary Data. The boundary data is used to verify that encroachment has been detected and to estimate the size of encroachment. When this re- search was started, there were seven Auckland regional councils and of those councils approached 2 of them, Manukau and North Shore supplied bound- ary data in GIS shape file format. Figure 5.2 shows four views of the same park, Normanton Reserve. Figure 5.2(a) is a digital aerial photograph obtained from the Auckland city council’s GIS viewer - note that the boundary is super- imposed in red. Figure 5.2(b) is a view of the council’s cadastral data, showing plot numbers and boundaries, produced using ArcMap software. Figure 5.2(c) is a view of the GPS points collected in a field survey produced using ArcMap software. Figure 5.2(d) is a view of the council’s cadastral data, overlaid with the GPS points collected in a field survey, produced using ArcMap software.

5.2. Park Data 63

(a) Wyllie Park (b) Teviot Reserve

(c) Auburn Reserve (d) Diana Reserve

Figure 5.1: Examples of public parks in Auckland.

5.2.1 Park Data Collection using GPS

After identifying the sites to be surveyed and obtaining existing maps and images, knowledge elicitation is carried out with the stakeholders. The stakeholders include residents living around the sites, non-residents who use the sites, organised sports groups and representatives of the Auckland Councils. During transect walks, local spatial and technical knowledge is integrated. Field surveys were carried out to lo- cate boundaries of land types/uses using GPS. GPS data is then be converted into vector objects. The data collected is analysed and integrated into a model. Then a current land use map is produced which is then be compared with the histori- cal/official land use map (obtained from the councils) to produce an ’areas of po-

64 5. Land Encroachment in New Zealand

(a) Council Viewer (b) Council Cadastral Map

(c) GPS data (d) GPS data and cadastral map

Figure 5.2: Visual Representations of park data.

tential dispute’ map.

One approach is to take data from three separate sources: cadastral data (offi- cial data) received from the Auckland council, GPS co-ordinate data (current data) collected during a field survey and GPS co-ordinate data (perceived data) collected during a field survey with the participants. The data is analysed and integrated in a GIS. The GIS is used to produce publicly acceptable visualisations of the discrep- ancies between the three sets of data. Validation of the approach is carried out by comparing the three sets of data. The approach is intended to detect discrepancies between the official data and the current data, the official data and the perceived data, and the current data and the perceived data.