1

Do state plane coordinates always begin as longitude and latitude?

In other words, they are not another system that can be calculated without Long. and Lat., correct?

I guess I'm saying, back in 1930+ they came up with the State Plane system. To make that work, however, they had to start with L&L. Today, I am guessing I can simply compare it to a database. But if for example, I have a GPS device and I want to know the Plane Coordinate, I have to convert it.

  • If you are asking a historical question, this article may be interesting to you. – Russ Sands Jul 13 '15 at 20:24
4

Almost all software for doing coordinate projection use geographic coordinates as a standard system in the middle and defines "forward" (from geographic to projected) and "inverse" (from projected to geographic) routines for projections.

So, to go from a UTM projection (say "UTM 10 N") to a stateplane projection (say "Washington Stateplane North") you'd first run the inverse projection from UTM to geographic, then run the forward projection from geographic to stateplane.

1

There are algorithms that will transform from a grid system to another grid system without going without requiring a conversion to lat-long. So the best answer I can come up with is not always, but often they use lat-long.

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