GPS Manager User Manual -- Distances and bearings

|  |  | Distances and bearings

## Distances and bearings

There are two sets of formulae for computing distances and bearings that the user may choose

1. the so-called Law of Cosines for Spherical Trigonometry, that is not very accurate but is quite fast, and
2. the modified Rainsford's Method with Helmert's elliptical terms with a high degree of accuracy but slower; this method cannot be applied if one of the points is a geographical pole, in which case GPSMan applies the Law of Cosines.

Experiments with them seem to indicate that the differences to be expected are in the range of less than 100 metres in distances of more than 10 kms, and no differences in bearings when they are presented in degrees as integers.

Bearings in GPSMan are always geographic (True North).

|  |  | Distances and bearings