Figure 15 Parameters required for the input of getGeoInfo

CS) Informative Maps on PDA-phones
Chui Pui Ling Page 28
getMapFromCentamap
Functionality To retrieve the map in GIF format from Centamap Input (Figure 18)
- Latitude
- Longitude
- Zoom Level Output GIF image with dimension of 800 x 600 pixels


Figure 18 Parameters required for the input of getMapFromCentamap
3.1.2. Maps manipulation and Coordinates Collection
There are different ways to manipulate maps. The most common method is to apply the maps from Lands Department and draw the required maps layer by layer. The coordinates in HK Grid 80 format can then be mapped with different areas of the map. On the other hand, such method is not being used in this project. Since SUNDAYLBS can return a specific map from centamap after the detection of the current location, the returned map can be applied directly. It not only shows the current location at the center point, but also it can be specified with different zoom levels. With the direct use of the centamap, it is much convenient. However, verification of the returned map is required. To collect the coordinates with the address information, my first attempt is to collect all the coordinates on the required map. However, the collected address information is duplicated for different coordinates. This is because a building is represented as an area on a map and it covers an area of coordinates. It would

CS) Informative Maps on PDA-phones
Chui Pui Ling Page 29 cause problems in route finding since there is no unique coordinates to represent a building and the entrance of each building maybe required to define manually. Therefore, sampling method is used for collecting the coordinates. First of all, sample points are taken from a sample map. The samples are then mapped with HK Grid 80 coordinates. With the coordinates, address information is retrieved via SUNDAY LBS [19]. This method is feasible because it is not necessary to consider all the coordinates on the map for route finding purpose and the mapping of coordinates to the map on the PDA-phone need not be very accurate. The following map (Figure 19) is used as an example in this project. The number shown in each node is the coordinate ID. It is a unique key of coordinates. Each coordinate ID consists of a standard coordinates in HK Grid 80 format as well as its corresponding address. The address information is retrieved from getGeoInfo of SUNDAY LBS web services [19].

CS) Informative Maps on PDA-phones
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