Is there any source describing the accuracy of OpenLayer's scale line? You can get an scale line by using the constructor:
However, it seems to be very inaccurate in relation to my geodesic measurements (0.5 km - 1.5 km difference depending on zoom). Is there any info I can cite to explain this different?
I'm using OpenLayers "Release 2.13.1" and OSM as base layer. I'm calculating the distance between point using WGS84 projection with 3 decimals and geopy distance module.
As an example, the distance between the points -2.416,55.703 and -2.434,55.698 is 2066.599 m according to my calculations and 2.5 - 3 km according to the scale line depending on zoom.
Ideally, the info I'm looking for is something like "the scale is accurate in +- 1 km because it calculates the distance using X method". The official doc (http://dev.openlayers.org/docs/files/OpenLayers/Control/ScaleLine-js.html) doesn't mention accuracy.