Hello.
I am using postgis 1.4 and following the instructions in PostGis in Action, I am trying to use real coordinates data (longitude and latitude) that they fetched from a google android mobile device to construct a polygon (I am going to use it as a query box).
Particularly, the loaded coordinates (lon,lat), which are translated as mobile user absolute position will be used as the origin of a circle, having as radius the positional_accuracy of gps device in meters.
So, having the user position in decimal degrees, the radius of a circle in meters, the yaw angle of mobile device embeded compass showing the direction of the user, I want to construct a geometry polygon. Namely, I want to find the four point cartesian coordinates of the polygon. I have some formulas but I cant get true results. I tried transforming WGS84 (EPSG:4326 coordinate reference system of lon lat coordinates) to a planar reference system as Tranverse UTM EPSG:32636 but till now I did not find the solution.
It seems that transformations create a huge polygon. Normally, I must create a polygon that depends from the distance between user position and a real world object that the user is observing. Increasing that distance the query window (polygon) must increase too.
If anyone can help I will really appreciate becuase I am stuck here and I have to deliver very soon my master of thesis LBS & GIS application.
Thank u very much.
Miltos Miltiadous
Postgraduating Information Systmes student in Open University Cyprus.
