Easy, 1 Latitude is the circumference of the earth divided by 360: 111 km
1 Longitude depends on your Latitude, so… copypaste
math.radians(6378137.0 * math.cos(math.radians(lat)))
Now, I know this all breaks down horribly when you consider large distances or require high precision(it also upsets mathematicians), but I don’t care(much).
All I^{1} am interested in is, if I stand at 42° Latitude and I walk North 10 meter, about what is my new Latitude?

And probably half the googlers and questioners on Stack Overflow. ↩