4
votes
1answer
138 views

MMqgis (hub distance) error in distance

So I am trying to calculate the distance of several points to a coastline, using hub distance (mmqgis plugin) in Qgis Dufour 2.01. I am using the default coordinate system (WGS84) and I, already, ...
2
votes
1answer
563 views

Getting points within a range from a postgres database?

ok so this is query i'm making which returns no result: SELECT building.gid FROM building WHERE ST_Dwithin(building.geom, ST_GeomFromText('POINT(long lat)',4326), 400) If I run this ...
27
votes
2answers
2k views

How accurate is approximating the Earth as a sphere?

What level of error do I encounter when approximating the earth as a sphere? Specifically, when dealing with the location of points and, for example, the great circle distances between them. Are ...