Process Repeats

Use the Gravity > Process Repeats menu option (GRREPEAT GX) to find all repeat readings in the master database based on the Station number, or combined Line and Station number. It calculates averaged values and displays repeat statistics for the survey. Repeat statistics can also be reviewed in a text report file.

Calculate Repeat Differences dialog options

Station channel	The name of the station channel to be used in identifying repeated readings at a location. Normally this is the "Station" channel. Script: GRAVRED.STATION
Data channel to average	The name of the data channel to average based on station repeats. Normally this is the "Gravity" channel. Script: GRREPEAT.IN
Output averaged channel	The name of a channel in which to place the averaged values. Normally this is "Gravity_Avg". Script: GRREPEAT.OUT
Determine repeats from	Choose: "Station only" if station numbers uniquely identify gravity stations. "Line and Station" if there is a "Line" channel and the line and station number must be used to uniquely identify a station. Script: GRREPEAT.LINE set to "No" or "Yes" to specify if the "Line" station should be used.
Select from repeats the:	If encountering repeated readings at a location select one of the Mean, Median, Min, Max readings. Script: GRREPEAT.MODE
Reorder by stations?:	Select the Yes option to re-order stations from Minimum to Maximum. Default is set to No. Script: GRREPEAT.SORT

Application Notes

The GX averages the repeated readings in the input channel and places the result in the output channel. A second channel named RepDiff is created to store the difference between the repeat readings and the average reading.

If encountering repeated readings at a location select one of Mean, Median, Min, Max of the readings.

If repeat readings are performed to determine the statistical quality of the data, the RMS error and the maximum error are significant statistics.

If repeat readings are performed to improve the data quality by averaging, you may wish to remove unacceptable readings. To do this, display the Station, Gravity, Gravity_Avg and RepDiff channels. You may then analyse these channels and determine if any of the readings should be removed. To remove a reading from the calculation, click on the reading row fiducial (left-most column), then right-clickand select "Delete Marked Rows/Fids". Run the GRREPEAT GX again and the eliminated reading will not be used in the calculation of the statistics. A series of dialogue boxes will show the repeat statistics and allow you to save the results to a report file.