tidwall / geodesic Goto Github PK

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Go package for performing accurate measurements of Earth. Includes the geodesic routines from GeographicLib.

License: MIT License

Go 100.00%

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zhanglei isgasho vendor86 stevenh

geodesic's Issues

Different order of adding points leads to wrong area calculation

In the sample code below, the area calculated for the second case seems to be wrong.

func TestArea2(t *testing.T) {
	var area, perimeter float64

	poly := geodesic.WGS84.PolygonInit(false)
	poly.AddPoint(10, 10)
	poly.AddPoint(10, 20)
	poly.AddPoint(20, 20)
	poly.AddPoint(20, 10)

	poly.Compute(false, false, &area, &perimeter)

	fmt.Printf("%f, %f\n", area, perimeter)

	poly = geodesic.WGS84.PolygonInit(false)
	poly.AddPoint(10, 10)
	poly.AddPoint(20, 10)
	poly.AddPoint(20, 20)
	poly.AddPoint(10, 20)

	poly.Compute(false, false, &area, &perimeter)

	fmt.Printf("%f, %f\n", area, perimeter)
}

Outputs:

1190968350339.391846,   4355689.472548
508874653373749.062500, 4355689.472548

[feature] geodesic buffer

Thank you for providing this valuable package in Go.
For geodesic calculation, one important feature is the geodesic buffer (on sphere). Currently, there is no Go library that works for this feature. ArcGIS does provide some APIs, but they are not flexible enough. I was wondering if you have any plans to add relevant functions in this package?

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