I have several coordinates provided in WGS 84 which I need to rasterize. For that purpose I simply interpret the lat,lon coordinates as x,y coordinates and I apply some scaling. So e.g. anything in the rectangle described by (54.3460005,10.1494873)(54.2984447,10.2002991) will be scaled to the rectangle (0,0)(10000,10000). In further processing steps this raster is translated back into the WGS 84 coordinate system.
I am aware of that this simple translation would be problematic for larger areas but I only look at smaller urban areas so I think the error introduced is acceptable. Further, visual inspection showed that the difference between my raster method translated back into WGS 84 coordinates and the original coordinates is practically neglectable. Yet I feel uncomfortable doing so without knowing the exact error I introduce by this method. At least I want to report it.
How can I calculate on a theoretic basis how large the error is which I introduce by simply interpreting lat,lon (WGS 84) values as x,y values?
EDIT: The error I am concerned about is the level of distortion of a pixel. While in the northern part of the map a pixel covers a smaller area (when being in the Northern hemisphere like my example), in the southern part the area covered is larger.