Hi Morton, Thanks for the email and for spotting the issue. Clearly Google is rounding the coordinates.
James On 24 July 2013 12:26, Morten Sickel <[email protected]> wrote: > If you look into the json google produces, you should see that the start- > and endpoints are identical - and they are neither equal to neigher your > start- nor endpoint I would guess there are some rounding going on > somewhere - that the google api just is not able to distinguish between > points so close together. > > > > Morten > > > James David Smith skrev: >> Hi there everyone, >> >> I've been messing about using the Google Directions API thing >> recently, and came across some odd results. Code to demonstrate is >> below. >> >> Essentially the distance between two points using PostGIS is 18 >> metres, yet when I translate the points to Lat/Long and then stick >> them in the Google API the distance comes out as 1 metre. >> >> Does anyone have any thoughts on this? >> >> Thanks >> >> James >> >> -------------------------------------------------------------------- >> -- Calculate a distance between two points using SRID 27700 (OSGB36): >> >> SELECT St_Distance( >> St_SetSRID(ST_makePoint(531058, 178463), 27700) , >> St_SetSRID(ST_makePoint(531041, 178455), 27700) >> ) >> >> RESULT = 18.7882942280559 (I presume metres) >> --------------------------------------------------------------------- >> -- Now calculte a distance between two points using SRID 4326 (WGS84): >> >> SELECT St_Distance( >> St_Transform(St_SetSRID(ST_makePoint(531058, 178463), 27700), 4326), >> St_Transform(St_SetSRID(ST_makePoint(531041, 178455), 27700), 4326) >> ) >> >> RESULT = 0.000256838311729703 (I presume degrees) >> >> --------------------------------------------------------------------- >> -- Now calculate the distance using the Google Directions API using >> the Lat/Lon values: >> >> http://maps.googleapis.com/maps/api/directions/json?origin=51.4899343224464%20-0.113689479559085&destination=51.4898663658699%20-0.113937164484113&mode=walking&sensor=false&units=metric >> >> RESULT = "1 m" >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >> > > > _______________________________________________ > postgis-users mailing list > [email protected] > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [email protected] http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
