Interpolate between 2 GPS locations based on walking speed

Question

Problem:

---

Given two locations:

L₁ = (latitude₁, longitude₁, timestamp₁), L₂

Answer 1

Calculations like these are actually very simple if you first convert your lat/longs to n-vectors (https://en.wikipedia.org/wiki/N-vector). After converting you can use standard interpolation, and you will also avoid any problems with long distances, the poles or the dateline.

If you check "External links" on the Wikipedia page, there is a page (http://www.navlab.net/nvector/) where ten problems are solved, and problem 6 on that page (interpolated position) should be the same as your question. As you can see, that solution is exact for any distance and also works at any earth-positions, like the poles.