Background Location Validation Test

Use the Background Location Validation Test option, (Geosoft.uxo.gxnet.dll(Geosoft.GX.UXO.UxaBackgroundValidationTest;Run)*), to determine whether a field location is suitable to collect background measurements.

Expand to see the locations (menus) where this option is available.

UX-Analyze extension:

• AGC Static Data > Sensor Tests and QC Tools
• AGC Expert User > Static Data Prep and QC

Background Location Validation Test dialog options

Raw Background Validation Data
Database prefix	Select the prefix for the background locations databases that contain the raw background location validation measurements (SBR). Script Parameter:UXANALYZE.BKGTEST_RECONPREFIX
Group name	Select the group name. Script Parameter:UXANALYZE.BKGTEST_RECONGROUP
Mask channel	Select the mask channel. Script Parameter:UXANALYZE.BKGTEST_TARGETMASK
TOI Reference Data
Database prefix	Select the prefix for the databases containing the data for the TOI reference item. Script Parameter:UXANALYZE.BKGTEST_TOIPREFIX
Group name	Select the group name. If the list is empty, the source database for the TOI Reference data does not exist. Run Invert for Sources (Static) to create the database*. Script Parameter:UXANALYZE.BKGTEST_TOIGROUP
ID channel	Select the ID channel. If the list is empty, the source database for the TOI Reference data does not exist. Run Invert for Sources (Static) to create the database*. Script Parameter:UXANALYZE.BKGTEST_IDCHANNEL
TOI description channel	Select the channel that contains description of the TOI. If the list is empty, the source database for the TOI Reference data does not exist. Run Invert for Sources (Static) to create the database*. Script Parameter:UXANALYZE.BKGTEST_DESCRCHANNEL
Selected TOI	Pick the TOI to use for the test. The list is populated from the values in Description channel. Script Parameter:UXANALYZE.BKGTEST_SELECTEDTOI
Response data channel	Select the channel that contains the TOI response data. Script Parameter:UXANALYZE.BKGTEST_DATACHANNEL
[More]
Background cluster distance (m)	Specify the search distance that is used to identify clusters of measurements for test location. Default value is 1.5 times the cart width (see the SBR Target database, UXA_Cart). The factor is defined in the configuration file, clusterWidthvalueMultiplier. Script Parameter:UXANALYZE.BKGTEST_SENSORWIDTH
Min. reference to surrounding measurement (m)	Specify the minimum distance from the reference background (centre) to the surrounding measurements. Default value is 0.25 times the cart width (see the SBR Target database, UXA_Cart). The factor is defined in the configuration file, clusterWidthminMultiplier. Script Parameter:UXANALYZE.BKGTEST_MINDIST
Max. reference to surrounding measurement (m)	Specify the maximum distance from the reference background (centre) to the surrounding measurements. Default value is 1.0 times the cart width (see the SBR Target database, UXA_Cart). The factor is defined in the configuration file, clusterWidthmaxMultiplier. Script Parameter:UXANALYZE.BKGTEST_MAXDIST
Sum of TOI to background amplitude threshold (m3/s)	Specify the sum of TOI to background amplitude threshold. Default value is 2.5. Script Parameter:UXANALYZE.BKGTEST_SUMOFAMPLITUDETHRESHOLD
Minimum polarization amplitude (mV)	Specify the minimum beta value. Default value is 0.001. Script Parameter:UXANALYZE.BKGTEST_MINBETA
TOI match metric	Specify the minimum combined match metric between the background measurements and the TOI. This threshold should define a high confidence TOI classification. Default value is 0.85. Script Parameter:UXANALYZE.BKGTEST_MATCHTHRESH
Background difference window start gate	Select the start gate to be used to calculate the sum of absolute differences between the reference background and the surrounding measurements. Default value is the first valid time gate (determined from UXA_GateFirstValidTime). Script Parameters:UXANALYZE.BKGTEST_STARTGATE
Background difference window end gate	Select the end gate to be used to calculate the sum of absolute differences between the reference background and the surrounding measurements. Default value is the first valid time gate plus two gates. Defined in the configuration file, windowGatesNumber. Script Parameter:UXANALYZE.BKGTEST_ENDGATE
Background location ID	The background location (cluster) ID can be generated automatically if Auto generate is selected. The starting number is 1. The current flag ID can also be used as the location, if the Use flag ID is selected. Default value is Auto generate. Script Parameter:UXANALYZE.BKGTEST_LOCATIONID_METHOD

Application Notes

*The Invert for Sources (Static) option can be found on the AGC Expert User > Static Data Inversion menu.

At the beginning of your project, you should establish locations to be used for background measurement to remove the effects of instrument drift and geology on the survey measurements. Additional locations can be established as required during the project.

To establish a location is suitable for background measurements, you need to ensure that:

• the area is "clean", that is, there are no metallic items in the vicinity.
• a TOI is detectable above the background noise level.

The test consists of static measurement at a central (reference) location and at least four surrounding measurements. The surrounding measurements are taken a distance ½ sensor width from the initial reference location and are evenly distributed.

For example:

1 2

 0

2 4

You also need to provide a reference TOI item. This should represent a worst-case scenario (i.e. smallest TOI item at maximum required detection depth). This is used to ensure the select TOI is detectable above any noise present in the background. This TOI data can be generated by either calculating the response of an item using library data (see Create Depth Response Curve Plot), or by collecting and processing data from an item on a test-stand (Import, Level, and Invert).

Process

The Background Location Validation Test tool will do the following:

• Manage the data
  • Group or cluster the measurements to identify background locations.
    • Determine which measurements are within the background cluster distance of each other.
    • Number the background test locations sequentially - the background ID.
    • Label each of measurements with the background ID.
  • Determine which measurement is the centre (reference) background location ID.
  • Label each of the measurements - location ID:
    • The centre location is 0.
    • The surrounding measurements are numbered from 1 to n, based on heading (i.e., clockwise from the North).
• Check location
  • Calculate distance and heading of each surrounding measurement to centre.
  • Identify measurements that are too close (Min. reference to surrounding measurement) or too far (Max. reference to surrounding measurement) from the centre/reference location.
  • Identify measurements that are not evenly distributed around the centre/reference location; there should be no more than approximately 120 deg between the surrounding measurements.
  • Subtract the centre (reference) measurement from each of the surrounding measurements (levelling the data to reference location).
  • Identify surrounding measurements where the difference of the sum of absolute value for the response (between the Background difference window start and end) is greater than the Sum of TOI to background amplitude threshold.
  • Identify background locations that have less than four valid surrounding measurements. Defined in the configuration file, surroundingMeasTolerance.
• Check noise and TOI detect ability
  • Add the TOI response data to the surrounding measurements:
    • Invert the surrounding measurement data and solve for a single object.
    • Determine combined library match with the TOI item. The combined match metric is the average of 111, 110, 011, and 100 match metrics.
  • Identify background locations that have less than four valid surrounding measurements.

Output

• Create databases of the results Static Background Validated – SBV:
• Target database -– will contain the metrics for each of surrounding measurement locations as array channels. There will also be two groups of background measurements:
  • Validated: the background locations that can be used for subsequent survey background QC checks and levelling.
  • Failed: the background locations that have failed the test.
• Data database -– will contain measurement data only for the valid background locations.
• Summary report/table (CSV), with following columns:
  • Location ID
  • Pass/Fail
  • X
  • Y
  • Combined metric match for each surrounding location (1 to n)
  • Difference of the sum of absolute value for the response over Window start to Window end (1 to n)
• Create a map and summary plot:
  • Generate a map that shows all the background locations with labels - clearly mark the background locations that fail, with date/time.
  • Generate a plot for each background location that shows:
    • The locations of all the measurements with labels - for the surrounding measurements that fail, the symbols are highlighted in red.
    • Polarization plots – show the polarization curves for each of the surrounding measurements with the TOI response added (in blue), along with the TOI Reference Item (in red). For surrounding measurements that fail, the title of the plot is highlighted in red.
    • Amplitude plot - for each surrounding measurement, sum of absolute response value for each gate, along with that of the TOI reference item.
    • A table listing the surrounding measurement metrics – surrounding measurements that fail are highlighted with an asterisk (*):
      • Surround measurement location ID
      • The distance from surrounding measurement to the centre measurement
      • The azimuth in degrees to surrounding measurements
      • The sum of the response over Window start to Window end
      • The combined match metric to the TOI Reference Item
      • Sensor ID
      • Low gate
      • High gate
      • Minimum beta (polarization) amplitude

Duplicate Identifiers

If the output database exists, the GX checks the input flag ids against the ones in the output database to make sure that no duplicate ID exists. If it finds a duplicate, it will issue a warning and ask the user to:

• Edit the input data by manually assigning a new flag ID to all the records in the cluster, or
• Pick the Auto generate option to create the background location ID, which is going to be maximum existing ID plus 1.