This is a really unfortunate title that seems like it might be interesting to general math-inclined people, but instead is only interesting to a very small group of engineers working in a very specific domain.
I just finished implementing enough of the WMTS spec interact with the one provider I'm using so far (UK ordinance survey). The only library I could find to help that works on Android was proj4j, which I'm using to handle converting points to different CRSs.
I'm making incredibly rookie mistakes like just realizing I need to project vector data into the same crs as the raster base map.
I want to be able to transparently support changing the base map to one with a different crs and lines and points recorded in the previous crs show up in the "right places", but I can't figure out how that's possible. I think I've seen other apps do it.