Test Criteria

The parameters for adjustment computations can either be set in the File tab under Info & Settings or from inside the Adjustments ribbon bar.

Info & Settings

Adjustments

Changes are stored with the project and applied to all future adjustment runs.

To set the adjustment parameters back to the default values:

To set the adjustment parameters back to the default values:

Go to the File tab and select the Defaults option in the Adjustment Parameters section under Info & Settings.

File

Defaults

Adjustment Parameters

Info & Settings

Level of Significance (α0)

Level of Significance (α0)

The α0 criterion determines the probability of rejecting a good observation. By default the level of significance is set to 5% as this is regarded as a good compromise. Setting the α0 value too low may result in a bad observation being accepted.

Power of Test (1-β)

Power of Test (1-β)

The 1-β criterion determines the power of the test, that is, the probability of rejecting a bad observation. By default the power of the test is set to 80% as this is regarded as a good compromise. Setting the 1-β value too low may result in bad observations being accepted.

The α0 and 1-β settings are subjective and should be determined by an experienced surveyor who carried out the field work. If you feel unsure about what α0 and 1-β should be set to, accept the suggested default values. For a theoretical background and further information on both these values, read the topic on the W-Test.

σ0 a posteriori

σ0 a posteriori

This is a global setting that can be used to compensate for the uncertainty of the value used as standard deviation of the unit weight. It affects the estimated precision of the adjusted coordinates and observations. You can, if necessary, choose to apply the σ0 a posteriori only in case the F-Test is not passed. The F-Test is a global test, that uses the ratio between the a posteriori and a priori σ0 as test statistics to verify the stochastic model applied in the adjustment.