Hi friends! I was recently tasked again with figuring out where stuff is in space. I decided this was an opportunity to cleanup the esqueleto library and releasing v4! Friends, I lied. I was in fact terrified I did the projections of geography wrong by using the geometry type, and hoped I could repair this by introducing distinctions between geography and geometry.

Turns out I was only using topology functions and as we all know¹ topology functions don’t change behavior based on projections (of space). Actually I was doing things right all along, except I didn’t know I was doing things right. Ignorance is bliss I suppose?

Anyway as a side effect we now do have full type distinctions between geography and geometry in esqueleto-postgis. This will allow you to do accurate measurements of distance for example over deformed spaces, such as spherical planet, and the library will guide you. This isn’t useful for me right now, but it may be in the future. Perhaps any of you guys do want to use it?

Aside from the type-safety goodness, I also cleaned house: We adopted wkt-geom which was unmaintained, allowing us to release on Stackage! Added st_dwithin for range finding, and st_distance for distance measurements, and restricted some functions to just geometry preventing runtime errors.

There is also this whole thing about SRIDs. Which appear to be localized projections of the earth on a map. It also includes details around units, going from meters, to feet, to degrees. I’m not happy with the current encoding but I doubt I need that a lot. The tools are there now in principle to transform between SRIDs. So you could have indexes and relations between various local maps for example. Let me know if you need a nicer encoding for this.²