[postgis-users] Calculate coordinates

[ots]

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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> 
> 

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