FAQ #6 Do I need a GCS?
GCS stands for Geographic Coordinate System.
I’m sure you’re familiar.
The GCS is a means for transforming global positioning, latitude and longitude, to an X,Y,Z location. That is, a flat cartesian (mapping) location.
In simple terms, we need a way to represent the position on the earth on paper. For those of you who think the earth is flat, I fear for you. For everyone else, this means converting the location on a sphere to a flat plane position.
Can we do this with a generic X,Y,Z coordinate system?
Yes, and the original version of photogeoDWG implemented an algorithm that did this, but it was inaccurate and inconsistent with other GCS. That wasn’t very useful.
When AutoCAD (and Civil3D) introduced GCS, it only made sense to take advantage of them, thus requiring a GCS before inserting camera positions, photos, and annotations.