point(x,y) versus point(lat, long) or What I Learned Today

At work I’m starting to experiment with some really cool GIS and starting to hook their data into useful applications. Hopefully I’ll get them out the door soon so I can show them off publicly.

Anyway, the lesson learned today is that points in GIS are not exactly the same as a point in math.

Math:

x,y

GIS:

lat, long

The problem is, latitude is actually a Y coordinate. Latitude refers to a point relative to the equator. Longitude is actually an X coordinate, since it is referring to a point relative to the Prime Meridian.

Moral of the story: when you’re reading a database of X, Y points on a map in decimal degrees to plug into Google Maps, you don’t want to plug them into the GLatLong function in that order. In other words, don’t use GLatLong(x,y) … it’s wrong. Use GLatLong(y,x).

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