Thanks! So the distance between each horizontal degree of latitude is always the same - 69miles or 111km - but the distance between each vertical degree of longitude decreases the further from the equator you get. Right?
Yes, each degree of latitude is 60 nautical miles, (exactly, on a Mercator projection), one minute of latitude is one nautical mile. Longitude is the same only on the equator, but decreases to 0 at the poles, 90 degrees north or south. That's why you always measure distance with the lat lines. 360 degrees to round the globe.