Building data collection

Once the map is visible, click the Locate Myself button to find the user's exact location. If the user's location point (blue marker) is not accurate on the map, then ensure one of the points is accurately placed by referencing yourself with the nearby roads and buildings displayed by the google maps and WMS layer. Then click at different positions on maps to create an approximate outline of the building using distance information shown between markers. If the user's location is accurately displayed on the map, then in that case, the user can walk to the edges of the plinth of the building and follow the blue marker that indicates the current location and place the markers accordingly.
The user can also turn the WMS layer on to view the pre-existing buildings.
If the user wants to delete one of the already placed markers, click on the marker to delete it.

Figure 4-5 Save Button on Map

The distance between the markers is shown on top of the markers. The distance can be visualized by following the sequence in which the points are marked. The distance between the first and second marker is shown on top of the second marker (12m). The distance between the second and third maker is shown on top of the third marker (11m), the distance between the third and fourth marker is shown on top of the fourth marker (12m) and the distance between the fourth marker and the first marker is shown on top of the first marker (10m).
Once the user is satisfied with the generated outline, click Save button to accept collected building information. Click Next button to proceed.
The user is prompted with a dialogue box requesting for Building Identification Number (temporary) and Tax Code of the building. Fill in the data and click ‘SAVE’ button. Then after, markers in the map are cleared.

Figure 4-6 Building data collection with site visit

Overview:
Physically visiting the site is recommended. Go around the building to get a rough idea about orientation and length of the building. Stay at a corner of the building where it has a clear and unobstructed view of a large portion of the sky. Nearby buildings and trees can prevent GPS signals from the satellites reaching the receiver. GPS receivers on phone need some time to first acquire signals from satellites, therefore allow couple of minutes to acquire signals from satellites.
Crossed Polygons are not accepted such as X-shaped polygons and polygons should not overlap with existing polygons or be on the top of the road layers. Additionally, ensure that opposite sides of the buildings are parallel to each other as far as possible.