#1727·turf

turf.square needs mercator coordinates to work correctly

Author: vin-niCreated Jul 7, 2019Updated May 13, 2026

Labels@turf/square

I've been struggling with getting a correct turf.square using real world coordinates until I realized I needed to pass mercator coordinates to make it work correctly on earth.

Maybe we could just add a hint in the docs or add a function that detects wgs84 coordinates and makes the correct calculation / conversion.

This is the result doing it with Wgs84 lat long: Bildschirmfoto 2019-07-07 um 03 12 39

And the expected result with conversion to mercator and back: Bildschirmfoto 2019-07-07 um 14 39 12

Quick code for the second result:

javascript

	var originalbboxx = [-2.440916, 49.4627643, -2.4579404, 49.4828877]
	
	var point1 = [originalbboxx[0], originalbboxx[1]]
	var point2 = [originalbboxx[2], originalbboxx[3]]

	var converted1 = turf.toMercator(point1);
	var converted2 = turf.toMercator(point2);

	var squared = turf.square([converted1[0],converted1[1],converted2[0],converted2[1]] )

	var squarept1 = [squared[0], squared[1]]
	var squarept2 = [squared[2], squared[3]]

	var wsg1 = turf.toWgs84(squarept1);
	var wsg2 = turf.toWgs84(squarept2);

	var newSquaredBbox = [wsg1[0],wsg1[1],wsg2[0],wsg2[1] ]

Source: Turfjs/turf

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