Calculate Euler Target Sizes

Use the Calculate Euler Target Sizes option (geosoft.uxo.gxnet.dll(Geosoft.GX.UXO.UxoCalculateTargetSize;Run)*) to estimate a size of the anomaly for each target.

The option is available from the following locations (menus):

UXO Land extension: Parameter Determination > Target Analysis

UXO Marine extension: UXO - Marine Mag

Calculate Euler Target Sizes dialog options

Grid to define target sizes	Specify the name of the grid to define target anomaly sizes. Script Parameter: UXPEAKSZ.GRID
Target database	Select the target database. Use the browse [...] button located to the right of the Target database field to select a different target database. Script Parameter: UXDETECT.TARGET_GDB
Group	Select the name of the "group"/line that contains the list of targets. This value is the same as the most recently specified target list from any of the other GXs that requires a target list. Script Parameter: UXDETECT.TARGET_GROUP
Mask channel	Select the target database mask channel to filter out specific targets. Only the targets with a mask (channel value) of 1 will be processed. If the value is set to 0 or dummy (*), the corresponding target will be ignored. If the field is left blank, no mask will be applied. Script Parameter: UXDETECT.TARGET_MASK
Output target size channel	Specify the channel to save target sizes. The default is "EulerTargetSize". Script Parameter: UXPEAKSZ.CHAN

Application Notes

To estimate the size of an anomaly in eight directions, the Calculate Euler Target Sizes GX determines the distance from the peak of an anomaly to the first inflection point. The median value of the eight distances is the anomaly size, and it has the same unit as the grid coordinates and is saved in the output channel.

The inflection points are found by examining sets of four successive points. From these four points, first and second differences are calculated. An inflection point is found when the second slope is negative and when the second difference (the change between the second and third slope) is positive. The inflection point is then between the second and third points and is determined from the calculated intercept of the second derivative values with zero. For this reason, the minimum target size found using this method will be no less than two grid cells.

The sizes calculated may be much smaller than the apparent sizes of target signatures as plotted on a map, because most of the target area is found on the "lower slopes" below the inflection point.

For magnetic data, the size data in this channel can be used as a starting point to determine the window size for the calculation of target depth and apparent weight user Euler's equations (see Calculate Depths and Weights using Euler Deconvolution). Euler's equations assume a square window centered on the target locations, and since the size is the distance to the inflection point, the length of a side of the window is two times the length determined by Euler Target Size. While larger windows may result in more stable/reliable Euler results, the windows should not include any adjacent anomalies. To visualize the windows on your data, see Plot Euler Anomaly Windows. Using the Euler Target Size as a starting point, you can manually enter larger window sizes to include the entire target anomaly of interest in the total field magnetic grid and some background data.

For EM data, this size data may be used as a grading parameter in UXO characterization.

*The GX tool will search in the "gx" folder. The GX.Net tools, however, are embedded in the Geosoft.uxo.gxnet.dll located in the bin folder. If running this GX interactively, bypassing the menu, first change the folder to point to the bin folder, then supply the GX.Net tool in the specified format.