Quality Control for your Induced Polarization Data This Quality Control for your Induced Polarization Data How-To Guide explains how to perform interactive quality control on your IP data. The IP QC Tool provides an interface for quality control operations on raw samples in the current IP database. With this tool, you can evaluate duplicate samples by navigating through the data by station and line number. The IP QC Tool is linked to the database, the pseudo-section plot and the 3D view. You have access to all these objects while running the QC tool and as a result, you can position the linked windows for optimal visibility.the data in the database are not changed during the quality control (QC) process. Instead, this process updates the QC flags (mask channel) to indicate which data points would be plotted, exported, and averaged. Quality control can be performed on both single-value and array channels. You can experiment with the Quality Control tools by working with the Iris Elrec-6 IP data set "IP6.DMP".This data can be found in the../program Files (x86)/geosoft/resourcefiles/data/ip folder. IP Quality Control Tool The image below depicts the IP QC Tool, which is the window through which you perform the IP QC operations. www.geosoft.com 1
The selected data is represented graphically in the upper right pane. All accepted samples are plotted in green. The average of the accepted samples are plotted in grey and the current sample is bordered in black. If there are no overlapping samples, the graph will simply be displayed in green. For reference, in the lower centre of the dialog the key IP channels are displayed. The following table describes the elements of the IP Quality Control dialog. 2 www.geosoft.com
Element Description A regular or array channel to QC. The Line to QC For the given line and channel, the data are sorted, first by the station, then by TX1 value. If the TX1 value is undefined, the data are sorted by station number only. Use the arrow keys to move through the data, one station at a time. Only raw data values (equivalent Type channel=0) are displayed. Averaged data values (equivalent Type channel=1) are skipped. Shows the current data element in the displayed array. Displays the absolute value of the highlighted element in the current window. This value is editable. When the edit box loses focus, the new value is committed to the database. The Cancel button does not recover from this permanent change. Check the Mask selected box to mask the selected data value. The mask check box is only active if an IP mask channel has been created through Create array mask channel. Check the Mask check box to mask out individual window elements of the array channel. The masked elements are excluded when averaging duplicate samples and are excluded from the calculation of the average curve. Two QC channels are available. Select the one to work with. Generally the on-time channels should be QC'd using the QC channel and the off-time channels using the QC_RES channel. The Acceptance options are linked to the QC channel values as follows: Accept: Values are used in all calculations and export operations. The QC flag in the database is set to 1. Flag: Values are ignored in calculations and export operations but are plotted as labels on pseudo-sections, enclosed in square brackets. The QC flag in the database is set to 2. Reject: Values are always ignored in plotting, averaging, and export.the QC flag in the database is set to *. www.geosoft.com 3
As one or more samples are flagged or rejected, the average is recalculated. Click to recalculate the values in the QC tool when the values in the database have been changed. Click to pump the changes from the QC tool back to the database. The data value range plotted along the left margin of the graph at the top and bottom, indicate the current range of the graph. The data section provides a graphic representation of the data for the selected channel. Each square represents the value of a data point. In regular channels, only one data point is shown for each sample. In array channels, data values for the same sample are connected with a line. The cross-hair cursor indicates the currently selected data point. To select another data value, click the left mouse button on the point. The colour of the sample line indicates the acceptance status of the sample. The colours are: Accept Green Flag Blue Reject Red Average Grey The currently selected sample is bordered in black. Use the mouse to select individual samples and windows. The following procedure guides you through the process of evaluating duplicate samples for an IP array channel. To Perform Quality Control on IP Data 1. From the IP menu, select Quality Control. The IP QC Tool appears. 2. From the Channel to QC dropdown list, select the desired channel. 3. From the Line to QC dropdown list, select the line to QC. 4. To have a quick view of the pseudo-section of the current line, click the Plot pseudosection of current line ( ) button. The psuedo-section of the current line will be plotted to an open map. 4 www.geosoft.com
The pseudo-section is linked to the IP QC Tool, the database and (if opened) a 3D view. You should position the data windows for optimum visibility, to enable you to better review your data. 5. Using the Grouping radio buttons, select Station or TX1. 6. From the Location dropdown list, or using the arrow buttons, select the location of interest. Since the IP channel is an array channel, the data appears in the data pane as a connected series of data values. Each data point represents the value of the data for a specific time window. The connecting line shows the signal decay over time. 7. Using the QC Channel radio buttons, select QC or QC_RES. 8. You can also correct an erroneous point. To modify the individual data values enter a new value for the selected data point in the Data Value text box. Press the Enter key to see the graph update. To update the database with your QC Tool changes, click the Pump ( ) button. To update the QC Tool with any changes made in the spreadsheet window, click the Recalculate button. 9. Click OK. In the QC channel of the database, an asterisk (*) indicates a flagged (or dummy) value. www.geosoft.com 5
This flagged sample will not be used in any calculations, exports, or plots. You can also edit the acceptance status of the data points directly by changing the numbers in the QC channel. Publication Date: January-07-16 Copyright 2016 Geosoft Inc. All rights reserved. 6 www.geosoft.com