Defining an arbitrary coordinate system

[troyswanson]

Greetings all,

I'm working with floor plan data for a retail store. This data is arbitrarily situated on an x/y plane with no respect to north (eg: the front of the store is always at the bottom of the grid). Each unit in the x/y plane is 1 inch, so things are to scale with a known measurement. I'm currently using Shapely to define the polygon features that are on this grid.

My goal is to be able to translate the data from this x/y plane to values that can be used in an IMDF manifest (which is essentially an extension of GeoJSON), so probably latitude/longitude.

Main question: What would be the necessary steps for converting this data to latitude and longitude?

My best guess right now based on my limited knowledge of this topic would be:

1. Define anchor points on the x/y plane that correspond to some CRS (maybe UTM?)
2. Do some kind of translation that moves the points based on the anchor points
3. Project the translated features from that CRS to latitude/longitude

Any help on how to tackle this problem would be greatly appreciated. Thank you!