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So I want to get the square formed by a single point of lat/lons, my plan was to take that point's latitude, divide by 360, and multiply by the circumference of earth. Giving us the distance from the equator.

Now I will take 1/4 the circumference of earth, and subtract by the distance from the equator, giving us the height of triangle T. I can the find the base because I know the initial height, truncated height, and the original base.

Now using the base and height I can use trig to find the minimum and maximum longitude, and the latitude is easy because lets are evenly spaced. Does this sound right?


Let me simplify this question.

How can I find the distance between two points of longitude, at a single point of latitude?

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marked as duplicate by whuber Apr 8 '13 at 17:25

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

The range of latitude values is not from 0->360. – nagytech Apr 8 '13 at 0:48
I think you need to work with Projected coordinate system and not geographic lat/lng since you cannot perfrom measurements with lat/lng. – artwork21 Apr 8 '13 at 1:03
Not sure what you are asking for exactly but maybe a look at Great-circle distance, the Haversine formula, and Vincenty's formulae will get you closer. – blah238 Apr 8 '13 at 1:25
Ya, Great Circlt Distance did it, thank you! – Brian Wheeler Apr 8 '13 at 1:50
Can you turn this into a comprehensive answer to the original question, paste it in below ("Your Answer") and click the tick (check) icon to make it "the answer"? Thanks – BradHards Apr 8 '13 at 3:10

2 Answers 2

So for me the answer was, because I dont need that much accuracy, to use the Great-circle distance formula.

distance of one degree of longitude = Cos( longitude ) * radius * ( π / 180 ).

Distance of latitude = about 69 miles / degree

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This formula is correct for distance along a circle (it appears in many places on this site) but it is not the great-circle formula: a circle of latitude is a great circle only at the Equator. To see how incorrect it can be, consider the distance from, say, Mexico City (19.25, -99) and Bombay (19.25, +73) (which aren't too far from the Equator as it is). Your formula gives Cos(19.25)*(73+99)*69 = 11,200 miles, whereas the correct distance is 9730 miles. That 13% error is large. – whuber Apr 8 '13 at 17:22

Are you familiar with python? If you are there's another post which covers your Question!

What tools in Python are available for doing great circle distance + line creation?

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