I am conducting a spatial econometrics study on housing prices.
In order to calculate spatial auto-correlation between house locations using some econometric software (like Matlab), I use decimal latitude/longitude coordinates of each house as the location in the entry of the program.
I was recently surprised by the question of a researcher asking me if the coordinates that I enter in Matlab are indeed Cartesian coordinates and not geographic ones? Otherwise, he said, estimates leads to wrong results! I didn't respond to him because I ignored the difference between geographic coordinates and cartesian coordinates.
Today I find in wikipedia the definition of the projected coordinate system that I use (Universal Transverse Mercator) that it "uses a 2-dimensional Cartesian coordinate system to give locations on the surface of the Earth". I am confused.
Are UTM coordinates already cartesian ones? If not, how are they related?