[postgis-users] Calculate coordinates

[Charles Galpin]

I think it's the projection. Google uses EPSG:900913 so try that.

hth
charles

On Apr 30, 2010, at 2:01 PM, ots wrote:

> 
> Hi,
> i used upgis_lineshift function, it works but not as well as needed. I
> prepared map, where you can see result. The problem is, that it is not
> perpendicular and when used in different directions with same distance
> function parameter, the distance is different. Point 1,2 is original and 3,4
> result of function, point 5,6 original and 7,8 result.
> 
> http://maps.google.com/maps/api/staticmap?center=na%20zborenci,Praha&zoom=18&size=1024x1024&maptype=roadmap&
> markers=color:red|label:1|50.07698059082031,14.416675567626953&markers=color:red|label:2|50.07749938964844,14.41646957397461
> &markers=color:red|label:3|50.0770728490573,14.4169079217053&markers=color:red|label:4|50.0775916478854,14.4167019280529
> &markers=color:blue|label:5|50.07719802856445,14.417106628417969&markers=color:blue|label:6|50.077693939208984,14.418004989624023
> &markers=color:blue|label:7|50.0769791612592,14.417227446888&markers=color:blue|color:blue|label:8|50.0774750719037,14.418125808094&sensor=false
> 
> I used query like 
> 
> select ST_AsText(upgis_lineshift(
> ST_GeomFromText('LINESTRING(14.416675567626953 50.07698059082031,
> 14.41646957397461 50.07749938964844)', 4326)
> , 0.00025))
> 
> Do you know, where is problem? I guess, it is connected with projection but
> no idea how to correct it. May be, concerning angles the method works well
> and when looking on the result placed on geoid, it is ok. But I do not
> understand, why the distance is too much different.
> 
> Thanks, Ota
> 
> 
> 
> Charles Galpin-2 wrote:
>> 
>> Check out the upgis_lineshift function on
>> 
>> http://trac.osgeo.org/postgis/wiki/UsersWikiplpgsqlfunctions
>> 
>> The resulting line will have endpoints that  you want.
>> 
>> hth
>> charles
>> 
>> On Apr 29, 2010, at 7:10 PM, ots wrote:
>> 
>>> 
>>> Hello,
>>> I have oriented line. The line is given as two points (WGS84). I need to
>>> calculate coordinates(also WGS84) of next two points on one side (left or
>>> right) of the line in the given distance so all 4 points make together
>>> rectangle. 
>>> Is there some function that can help me? I was searching but no idea.
>>> 
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