About Local Reliability Zi

The local reliability describes how controlled a measurement is, and how likely it is that a gross error will be detected. Zi is dependent on the network design.

The local reliability Zi [%] is a reliability factor that represents the distribution of the over determination of the network on the individual observation (redundancy number).

• A value of 100% indicates that the observation is totally controlled.
• A value of 0% indicates an observation that is not controlled, that means, a possible gross error can not be detected, and Nabla is infinite. For example, for points that have been measured only once, Zi is 0%.
• For example, if an observation has a local reliability of 10%, only 10% of a possible measurement error would be visible in its residual, that means the error could not be detected.
• A value of 20% indicates a measurement that is well controlled.
• Values between 25% and 60% indicate a well designed network.

Click the Analyze Local Reliability link to open the Result dialog box. In the Result dialog box, on the Measurement Results tab, click the header of the Zi column to sort for the Zi values.

Select the row of the measurement, right-click and click Show Station to open the Measurement dialog box for the station on which the point has been measured.

• Green light indicates that all measurements are controlled, and all Zi are > the defined threshold for the Local Reliability.
• Yellow light alerts you that for some observations no Zi value could be determined. For example, for points that have no over determination. Continue, if you want to include detail points that are only measured once.

  If your measurements do not contain single measurements, check the configuration, or the tolerances.

  If you want to allow single measurements for some points, modify the field code list, and select the Single option. See Field Code Settings for Calculation.

• Red light indicates that the some measurements are not controlled, and have a Zi < the defined threshold for the Local Reliability. The list displays the 5 observations with the smallest Zi values. Click the Show link to open the Result dialog box.