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Calculation Parameters

Calculation parameters control or affect the result of adjustment and detail calculations.

Point Parameters

Preliminary coordinates affect how many iterations must be completed and thus the time consumption. If the preliminary coordinates are very poor, the calculation will be aborted after the maximum number of iterations has been completed or the calculation is found to diverge.

Tip

Use the best possible preliminary coordinates to reduce the number of iterations and processing time.

Station and Observation Parameters

The values of the measured quantities obviously have a direct impact on the result. Observations also have other important parameters that affect the calculation:

  • Coordinate system:
    The correct coordinate system has direct implications for GPS vector calculations and single point measurements.

  • Pressure and temperature (during distance measurement):
    If the distances are already corrected for pressure and temperature, these fields remain empty. Pressure is specified in mmHg, and temperature in degrees Celsius.

  • Corrections:
    An important question is: What corrections have been applied to the observations, either in the instrument or afterward? This is particularly relevant when manually registering historical observations.

Standard Deviation and Instrument

Standard deviation (accuracy) for different observations is calculated in different ways, depending on the observation type:

  • Conventional measurements (telescope measurements):
    Standard deviations for distance, vertical angle, and direction are specified in meters and gon. These standard deviations are transferred directly from the instrument when closing the observation dialog with OK. If values already exist, they are not overwritten (unless they are equal to 0).

  • Satellite vectors:
    Standard deviation of the vector component is imported from a file and converted. It's also possible to calculate standard deviation from instrument parameters.

  • Leveling:
    Standard deviation for height measurements, standard deviation, and distance-dependent component are stored in the instrument definition.

  • Single point measurements:
    Standard deviation is imported from a file and possibly converted to the map plane. It's also possible to use standard deviation from the instrument, where these are specified in the map plane with north, east, and height.

Note

Standard deviations used for conventional observations are based on the instrument's assumed standard deviation (accuracy). When an observation is a result of averaging multiple observations, the standard deviation should be adjusted accordingly. The standard deviation of an averaged observation is the standard deviation of the individual observations divided by the square root of the number of individual observations.

Calculation Type

The calculation type determines whether the calculation is performed in Horizontal, Height, or 3D. You will be asked about this when selecting the calculation function.

Info

When selecting 3D calculation, the program will perform a combined calculation of both horizontal plane and height.

System Values

For detailed information about coordinate systems, instruments, and correction codes, we recommend using the dialog help available under Settings for Gemini Terrain on the toolbar.

Instrument

Instrument definitions have a significant impact on the standard deviations assigned to observations, and thereby affect the weighting of observations in the adjustment calculation.

Tip

For more detailed information about instrument values, see the dialog help for instrument settings.

Calculation Options

The surveying application layer has a separate tab for calculation options. Normally, the default values suggested by the program can be used, but it's important to understand what they represent and how they affect the calculation.

Note

See the dialog help for a detailed explanation of the various calculation options.