2. Distance

Figure F-1
Distance Observation

Equation F-1 is the distance bertween two points in terms of their coordinates.

  Equation F-1

NA, EA: At point coordinates
NT, ET: To point coordinates
vD: distance residual

To apply a Taylor Series, patial derivatives of Equation F-1 are taken with respect to each coordinate of both points. The partial derivative for NA is:

Similarly, the remaining partial derivatives are:

Equation F-2 is the distance observation equation, evaluated at initial coordinate approximations.

  Equation F-2
Equation F-3