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Adjustment

Whether the adjustment is performed in the horizontal plane, height, or 3D (horizontal+height) is determined by the selected calculation type. This is chosen each time a calculation is run.

An adjustment point is a station point that does not have known coordinates in all existing dimensions.

Point status is U and the symbol is as shown below.

Adjustment point

We can also choose scale as an additional unknown in the adjustment, but this is normally not used.

Note

Detail points can be calculated as adjustment points if the point status is changed to adjustment point (D->U). The opposite is not possible. This may be relevant if we have measured the point from multiple stations and want to include it in the overall adjustment.

Limitations and Requirements

  1. In principle, there are no limitations on the number of observations that can be included in the calculation, or on the number of unknowns. In practice, the time consumption will set limits on how many one has the patience to use.

  2. The coordinates must be pre-calculated and not deviate too much from the "correct" value.

!!! tip The error message "Calculation diverges" is often caused by pre-calculated points with too rough coordinate values.

  1. Horizontal and height are calculated TOGETHER when you choose calculation type 3D.

  2. Sets must be reduced before calculation.

Observations Included in the Calculation

  • All distances and directions between selected points, or selected points and known points.

  • If there are direction observations from known points to selected points, other direction observations in the set will also be included if they go to known points.

  • For height calculation, only those vertical angles that meet the following requirements are used:

  • Goes to or from a selected point
  • If the vertical angle goes to or from a known point, its height must be known

  • Instrument height and target height must have values for the station/observation respectively

  • All satellite vectors are included in the calculation converted to direction, distance, and vertical angle.

  • Single point measurements in the map plane with associated (possibly converted) standard deviations.

Distances are calculated from the horizontal coordinates of the points.

Important

Distances are NEVER included directly in the height calculation. For reduction of vertical angles, distances calculated from the coordinates in the point list are used if the height is missing.

Adjustment Calculation (Theory)

When you start an adjustment calculation, it will proceed according to the following principle:

  1. It is based on preliminary coordinates for the unknowns (pre-calculated by the program).
  2. For each observation, an error equation is created.
  3. The program forms normal equations and solves the system. The program calculates the unknowns (coordinates), their standard deviations, and error ellipses for the points.

The verification that the calculation is correct is ensured by, among other things, the size of the residual errors (adjustment corrections), see calculation documentation.