I'm working on a project where I have clusters of GPS coordinates to store, let's say ~20k points per cluster. The clusters overlay with big cities, like London or New york. I have many clusters around the globe, so the data isn't local (this could be important for the SRID).

I'm wondering what PostGIS type I should use to store this data, geometry or geography?

Once this data is stored, I'll mainly do only two kinds of computation (but I'll have to do them many many times so speed matters here):

• "Give me the points that are within 5 km of this particular point"
• "Is this point within 2-5 meters of this other point?"

My assumption is that geometry with the EPSG:4326 SRID should be good enough for this, since my distance measurements won't cover long distances. For the second point, I really need the accuracy though.

Is my assumption right?

I'm working on a project where I have clusters of GPS coordinates to store, let's say ~20k points per cluster. The clusters overlay with big cities, like London or New York. I have many clusters around the globe, so the data isn't local (this could be important for the SRID).

I'm wondering what PostGIS type I should use to store this data, geometry or geography?

Once this data is stored, I'll mainly do only two kinds of computation (but I'll have to do them many many times so speed matters here):

• "Give me the points that are within 5 km of this particular point"
• "Is this point within 2-5 meters of this other point?"

My assumption is that geometry with the EPSG:4326 SRID should be good enough for this, since my distance measurements won't cover long distances. For the second point, I really need the accuracy though.

Is my assumption right?