# To configure the survey style for a site calibration

1. Tap and select Settings / Survey styles. Select the required survey style.
2. Tap Site calibration.

3. Select whether the calibration computation should fix or compute the horizontal scale factor and the horizontal rotation.

   To fix the values, select the Fix horizontal scale to 1.0 check box and the Fix horizontal rotation to 0 check box. To compute the values, clear the check boxes.

   Selecting these check boxes is recommended if you are working in a modern well-defined coordinate system with a reliable transformation from the global reference frame and using a high quality local control within that coordinate system. You should clear these check boxes if GNSS measurements need to be scaled and/or rotated to fit the local control.

4. Select the type of Vertical adjustment to be computed and applied:

   - The Constant adjustment only option will compute a vertical shift value to best fit the calibration point measured elevations to the control elevations. This setting is recommended if you have an accurate geoid model.
   - The Inclined plane option will compute a vertical shift plus north and east inclinations to best fit the calibration point measured elevations to the control elevations. Use this model if you do not have an accurate geoid model, or if the geoid model is not a good fit to your vertical control.

   Clearing the Fix horizontal scale to 1.0 and Fix horizontal rotation to 0 check boxes and selecting the Inclined plane option will generally result in smaller residuals. However, unless you have high quality control, precise measurements, and a large project area, these smaller residuals are a result of overfitting your measurements rather than being a true indication of the quality of your site calibration.

5. For the Trimble Access software to automatically perform a calibration when you measure a calibration point, select the Auto calibrate check box. To switch automatic calibration off, clear the check box.

6. Select an observation type appropriate to a calibration point. The options for a calibration point are topo point or observed control point.

   If you set the observation type to Topo point, all settings are defined in the survey style for a topo point.

7. If necessary, set the tolerances for maximum horizontal and vertical residuals, and maximum and minimum horizontal scale settings. These settings only apply to automatic calibration and do not affect manual calibration.

   You can also specify the maximum slope of the vertical adjustment plane. The software warns you if the slope in the north direction or the slope in the east direction exceeds this. Generally the default settings are appropriate.

8. Specify how the calibration points you measure will be named:

   - In the Method field, choose one of the following options: Add prefix, Add suffix, or Add constant.

   - In the Add field, enter the prefix, suffix, or constant.

   The table below shows the different options and gives an example of each.

   Option | What the software does | Example value in the Add field | Grid point name | Calibration point name
   --- | --- | --- | --- | ---
   Same | Gives the calibration point the same name as the grid point | – | 100 | 100
   Add prefix | Inserts a prefix before the grid point name | GNSS_ | 100 | GNSS_100
   Add suffix | Inserts a suffix after the grid point name | _GNSS | 100 | 100_GNSS
   Add constant | Adds a value to the grid point name | 10 | 100 | 110

When a site calibration is computed in a job where a site calibration has not been computed previously, the settings from the currently selected survey style are used. You can change these settings by tapping Options in the Site calibration screen, making the necessary adjustments, and then tapping Accept. These changes are used for the job but are not written to the current survey style. When a site calibration is computed and stored in the job, the settings used in that computation are stored in the job along with the site calibration details. If you return to the site calibration function later in the same job, the settings from the job database used for the previous site calibration computation are used in preference to the settings in the current survey style, which may differ. To restore the settings from the current survey style, tap Options and then tap the Default softkey. This populates the options from the current survey style. Tap Accept to use the survey style settings in the recomputation of the site calibration.