I'm designing a GPS constellation for KerbalGPS Revived - thanks to USN I understand the geometry of CPA, and that leads me to realize there's a problem:

If the transmitter has a range of 2,500km and I put it in a 2,500km orbit - it's only in range of a given receiver when it's exactly overhead. The maximum orbit height (yielding horizon-to-horizon coverage) is actually defined by a tangent 2500km long, originating at the receiver. So my question would be, what is the orbital altitude defined by the endpoint of the tangent?

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## DerekL1963

I'm designing a GPS constellation for KerbalGPS Revived - thanks to USN I understand the geometry of CPA, and that leads me to realize there's a problem:

If the transmitter has a range of 2,500km and I put it in a 2,500km orbit - it's only in range of a given receiver when it's exactly overhead. The maximum orbit height (yielding horizon-to-horizon coverage) is actually defined by a tangent 2500km long, originating at the receiver. So my question would be, what is the orbital altitude defined by the endpoint of the tangent?

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