Efficient way of iterating a list of records

[anguis]

In case of traditional computational environment built on top of Python (numpy+pandas+python), that would be a quite simple problem. NumPy is implemented in C and aimed at computationally efficient workflow with arrays in Python.
But it is not clear, would it possible to install NumPy on your GPS module?!
You will likely need to implement Haversine distance using NumPy to get
numpy-vectorized form of the distance function.

Sadly I think the answer is no That's the trouble with embedded implementations; they often contain a pretty basic or stripped down
interpreter. I'm aware of the Haversine calculation thanks, and fortunately trig functions are supported although in this case I'm after relative comparisons rather than absolute distances so I'm hoping I can work with lat/long values directly (happy to be corrected though!)

So it's back to manually trawling through the records and the best way to do it...