Hello I'm a newbie in maps and not so good (as I wish to be...) in math and geometrics stuffs.
So: I have a 2d google map.
I have to put a 2d projection of this map (not exactly this one but a handpainted one, so I will not violate any copyright) in an app (that must work offline, so I cannot use external API but only math resources on the smartphone):
I need to put a locator (on this projection) in real time, calculating it from GPS position of the user.
So, e.g. if the user is here (45.064768 N, 7.695454 E), I will put the locator here:
In other words, I need to know how can I calculate X and Y distance from the upper left corner of the projection (I know the GPS position of all four corners of the projection).
I understand that is a strange question, that I 've asked before on SO (but I was downvoted and informed about this site). I also seem to understand that this math calculation has something to do with a rotated perspective grid:
Pls I don't need the final "copy and paste" solution but only an idea on how to proceed, explained in words as simple as possible.
Then, if I will observe this shape from behind, this isosceles trapezoidal view will become a perspective view (what I want to show in my app) but with a rectangular shape, due the inclination (no more from the top but e.g. from 45° degrees):
Considering a given point on the "flat" map, I can get distance and angle from the four vertex of the isosceles trapezoid.
Then, I must "transpose" these distance and their angles on the resulting rectangle. I think it can be quite easy to do so, although I believe there'll some errors doing in this way (due to a lot of missing other parameters):