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# Find the area of a map (Xkm x Ykm) from the left & right longitude and latitude

 0 How can the area of a map from OpenStreetMap be determined in the form of Xkm x Ykm, given the following information: Left Longitude = 103.554879 Right Longitude = 103.740497 Top Latitude = 1.585770 Bottom Latitude = 1.490873 Any ideas? Thanks a lot! asked 13 Oct '15, 10:47 amatek 11●1●1●2 accept rate: 0% 1 (13 Oct '15, 12:24) scai ♦

 1 This isn't a simple question, as the answer won't be a square as the Earth isn't flat, so the bottom edge will be a different length to the top edge. Additionally because of the spherical bulge the surface will be greater than the 'flat' area. I think this might answer your question if you're willing to approximate the Earth to a sphere. Edit: Of course this won't be in the format Xkm x Ykm but give the area in square km, if you specify a value for R, the radius of your spherical Earth, in km, for which 6,371km is an approximation. answered 13 Oct '15, 11:37 EdLoach ♦ 19.5k●16●156●280 accept rate: 22% Thanks for your response. Actually, I downloaded a map enclosed by those coordinates to be used in a large-scale simulation. Since the image is in XxY format (resolution of 17,408 x 9,216 to be precise), I would like to get an approximate value for my simulation area. (13 Oct '15, 11:50) amatek
 4 This is not an OpenStreetMap specific question and should better have been asked at a general GIS or geography Q&A site. (Edit: I see it was cross posted. Not generally a recommended practice as it wastes helpers' time.) You can use PostGIS for this. PostgreSQL with the PostGIS extension is a database system but often handy to do quick geometry or geography calculations like this: ``````# select st_area( st_setsrid( st_makebox2d( st_makepoint(103.55487,1.490873),st_makepoint(103.740497, 1.585770) ), 4326)::geography); st_area ------------------ 216753707.811525 (1 row) `````` The area is returned in square metres. answered 13 Oct '15, 13:11 Frederik Ramm ♦ 82.5k●92●720●1273 accept rate: 23% Thanks a lot. Since the image has a resolution of 17408x9216, the area should then be around 141723578m x 75030130m ? (13 Oct '15, 13:49) amatek No, 141723578 * 75030130 is 10633538481405140 and not 216753707. Your aspect ratio seems to be about 1.88:1, so you're looking at an area of perhaps 20186 * 10737, assuming the earth is flat. (13 Oct '15, 16:43) Frederik Ramm ♦

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question asked: 13 Oct '15, 10:47

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last updated: 13 Oct '15, 16:43

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