[postgis-users] PROBLEM CONVERTING AND MANIPULATING LONGITUDE AND LATITUDE COORDINATES

[Miltos Miltiadous]

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.  

         

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20100122/ffc7bc3c/attachment.html>