Average Repeats

Use the Gravity > Average Repeats menu option (geogxnet.dll(Geosoft.GX.Gravity.AverageRepeats;Run)*), to find all repeat readings in the selected channels based on the station number or based on the combined line and station number. Averaged values are then calculated and the repeat statistics for the survey are displayed. Repeat statistics can also be reviewed in a text report file.

You have the option to average only those multiple readings of the same station that are consecutive in time.

Average Repeats dialog options

Lines to process

You have the option to calculate the average repeats for the current line, selected lines or all lines in the database.

Script Parameter: GRREPEAT.LINE_SELECTION [D – Displayed line, S- Selected lines (default), A- All lines]

Station channel

Select the channel to be used in identifying repeated readings at a location. If the current database has a "Station" channel, it will be automatically selected.

Script: GRAVRED.STATION

Channels to average

Select the data channel(s) to average based on station repeats. Usually this is the corrected gravity channel; however, you can select multiple channels in the database to average in one run.

The repeated readings in the input channel(s) are averaged and the results are placed in the output channel(s).

The output channel(s) will be named based on the input channel(s) and suffixed by the type of averaging. For example, if the input channel is "Gravity" and the Statistical component selection is "Mean", the output channel will be named "Gravity_Mean".

Furthermore, a difference channel with the suffix _RepDiff is also produced but not loaded. This channel holds the difference between each repeat reading and the averaged value for that station.

Multiple channels can be supplied to the script by separating them with a semicolon (;). Example: Gravity;Elevation;Drift.

Script: GRAVRED.CHANNELS

Statistical component

Select the method to use when averaging readings at a location:

  • Mean
  • Median
  • Minimum
  • Maximum

Script: GRREPEAT.MODE

Determine repeats from

Select one of the two options:

  • 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 [0 – station only (default), 1 – line and station]

Average consecutive readings only

Selected by default, this option will average only the station readings that are consecutive in time. This will result in the same station being averaged multiple times if the station is visited more than once during the day.

Readings are considered consecutive as long as one reading is <=5 minutes from the subsequent reading. Readings that occur from one hour to the next are also consecutive as long as they are less than five minutes apart.

Uncheck this option to average all stations with the same number regardless of how far apart in time they are.

Script: GRREPEAT.AVERAGECONSECUTIVE [0 – No, 1 – Yes (default]

Reorder by station

Check this option to reorder stations from minimum to maximum. By default, the option is unchecked.

Script: GRREPEAT.SORT [0 – No (default), 1 – Yes]

Export averaged database

Optionally, export the averaged data to a database. The output channels are in this case saved in both input and output databases. All dummies will be removed from the output database.

The output database is saved in the project folder and opened in the current project workspace.

Script: GRREPEAT.EXPORT [0 – No (default), 1 – Yes]

Output database

Specify the name of the output database.

Script: GRREPEAT.OUTPUTDB
[More]

Click to expand this section and select the date, time, and line channels.

Date channel

Select the date channel name. If the current database has a "Date" channel, it will be automatically selected.

Script: GRAVRED.DATE_CHANNEL

Time channel

Select the time channel name. If the current database has a "Time" channel, it will be automatically selected.

If the date channel is supplied, the time channel will be used to sort the data. If the time channel is absent in the database, the date channel will be ignored.

This is a required field when the option Average consecutive readings only is selected. (It will be used to identify breaks in consecutive time readings to produce averaged values in the respective output channel.)

Script: GRAVRED.TIME_CHANNEL

Line channel

Select the line channel name. If the current database has a "Line" channel, it will be automatically selected.

When the option Line and station is selected, this channel will be used to uniquely identify a station on different lines.

Script: GRAVRED.LINE_CHANNEL

Application Notes

The GX averages the repeated readings in the input channel(s) and places the result in the output channel(s). A second channel named "<output channel>_RepDiff" is created for each of the selected channels to store the difference between the repeat readings and the average reading.

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 channel, the input and output channels, and the _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-click and select Delete Marked Rows/Fids. Run the GX again, and the eliminated reading will not be used in the calculation of the statistics.

A series of dialog boxes will show the repeat statistics and allow you to save the results to a report file: "Average_Repeats<date>.log".

*The GX.NET tools are embedded in the geogxnet.dll file located in the "...\Geosoft\Desktop Applications \bin" folder. If running this GX interactively, bypassing the menu, first change the folder to point to the "bin" directory, then supply the GX.NET tool in the specified format. See the topic Run GX for more details on running a GX.NET interactively.