Great-circle paths

[tdammers]

The Geodetics.Path module is great and super useful; one thing I would love to see there would be a greatCirclePath function that takes a lat/lon/alt point and an initial bearing, and generates a great-circle path from there. greatCirclePath 0 0 0 would thus generate the 0 meridian, greatCirclePath 0 0 90° would be the equator, etc.

This would be particularly useful for a thing I'm doing, which is about air navigation; essentially I have a VOR beacon that gives me a position and a bearing ("radial"), and a DME beacon that gives me a position and a distance, and I want to calculate the coordinates of the intersection between the VOR ray and the DME's equidistance sphere. I haven't quite dived into the code enough to do it myself yet, but if that's what it takes I'd be happy to.

[PaulJohnson]

Have you considered the rayPath function? It projects a ray in space, but the ground track of the ray is a segment of a great circle. Obviously that won't go all the way around, but it should be far enough for the application you have in mind. Also, a line through the projection point of a stereographic projection will give you a great circle when you map its points back to the ellipsoid. Neither of these will give you an accurate geodesic distance along the path, but I don't think your applicaton needs one. BTW, dont forget that circles on the ellipsoid map to circles on a stereographic projection. That might be useful tooPaul.On 20 Jul 2018 07:17, Tobias Dammers [email protected] wrote:The Geodetics.Path module is great and super useful; one thing I would love to see there would be a greatCirclePath function that takes a lat/lon/alt point and an initial bearing, and generates a great-circle path from there. greatCirclePath 0 0 0 would thus generate the 0 meridian, greatCirclePath 0 0 90° would be the equator, etc. This would be particularly useful for a thing I'm doing, which is about air navigation; essentially I have a VOR beacon that gives me a position and a bearing ("radial"), and a DME beacon that gives me a position and a distance, and I want to calculate the coordinates of the intersection between the VOR ray and the DME's equidistance sphere. I haven't quite dived into the code enough to do it myself yet, but if that's what it takes I'd be happy to.

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