There's other stuff that's undefined, for example Longitude = longitude * 10**7.
What are the units of longitude? - I think it's degrees, what's the valid range? - I think it's +- 180E7, Is it positive going east/west? - I think it follows the east is positive convention. I inferred this by digging through the code and looking at how it is used, but shouldn't have to do so for a fundamental data type.
I am working on a PR to do GPS blending at the moment, so will update the documentation for this data type at the same time.
I think we should specify it as being WGS-84. The height datum used is a significant issue when combining data from different GPS receivers.