Review of Run App

With regards to distance accuracy on the RUN app I have done some real world tests.

I have done any experiment with only taking every 1oth fix to calculate the distance delta. This worked better but still not right.

I have a loop round the backstreet, top of the next road and back. Initial attempt using the existing Bangle calculation came out at 560m. Considering I hade only recorded 320 steps I knew this was iffy.

I changed the calculation to the Equirectangular approximation as per:
https://www.movable-type.co.uk/scripts/latlong.html
I have used this before and found it pretty accurate on Kitchen Combo and WayPointer.

function radians(a) {
  return a*Math.PI/180;
}

// distance between 2 lat and lons, in meters, Mean Earth Radius = 6371km
// https://www.movable-type.co.uk/scripts/latlong.html
function calcDistance(a,b) {
  var x = radians(a.lon-b.lon) * Math.cos(radians((a.lat+b.lat)/2));
  var y = radians(b.lat-a.lat);
  return Math.round(Math.sqrt(x*x + y*y) * 6371000);
}

Changing to this calcualtion I then recorded 336m. Where my AmazFit Bip recorded 0.24 miles.
This is much more beleivable but I need to test against a dedictaed hand held GPS over a longer distance as I know the Amazfit Bip GPS is said to have some issues.