Calculate Forward Models
Use the Calculate Forward Models option (geosoft.uxo.gxnet.dll(Geosoft.GX.UXO.UxaForwardModeling;Run)) to calculate the electromagnetic (EM61) and magnetic responses for a range of target and sampling scenarios.
This tool is developed in partnership with Acorn Science and Innovation (AcornSI).
Forward Modelling dialog options
Sensor type | Select the sensor type: EM61mk2 or Mag [Default]. Script Parameter:UXANALYZE.FM_SENTYPE |
Output database | Specify the output database name, which is used to save the targets. Script Parameter:UXANALYZE.FM_OUTPUTGDB |
Target Definition - Parameters | |
X (metre) | X coordinate of the target relative to the data chip; 0 is the centre of the chip. |
Y (metre) | Y coordinate of the target relative to the data chip; 0 is the centre of the chip. |
Size | Size of the target. Select from a list of munitions and clutter items. |
Distance below sensor | The distance from the sensor to the target. |
Inc (deg) | Inclination of the target (EM61 mk2). Inclination of the target's dipole (Mag). |
Dec (deg) | Declination of the target (EM61 mk2). Declination of the target's dipole (mag). |
Roll (deg) | Roll of the target (EM61 mk2). |
Mod Error | Modelling error of the target. Read only This parameter will be populated after Invert is clicked, and only have value for the Inverted column. |
Target Definition - Parameter Loop | |
Target ID | Select the target ID from the list of targets entered in the target list. There is an empty option. If the empty option is selected, the entire Parameter Loop section is disabled as well as the Run Loop button. Script Parameter:UXANALYZE.FM_TARGETID |
Parameter | Select the parameter to change. The list includes: ID, X, Y, Size, Depth, Inc, Dec, Roll. Roll is disabled for Mag sensor. Script Parameter:UXANALYZE.FM_PARAMETER |
Minimum | Specify minimum value of the selected parameter. Script Parameter:UXANALYZE.FM_MINIMUM |
Maximum | Specify maximum value of the selected parameter. Script Parameter:UXANALYZE.FM_MAXIMUM |
Increment | Specify incremental change of the selected parameter. Script Parameter:UXANALYZE.FM_INCREMENT |
Current | Specify the current value of the selected parameter. Can be changed via the slider bar. The default value is the Minimum value. Script Parameter:UXANALYZE.FM_CURRENT_VALUE |
Background Noise | |
Database | Specify the database file name to use for background or site noise. Contains the data from the real sites, which will be added as noise to sensor response values. Populated with the list of databases in Project Explorer. Sorted. Database should exist. Script Parameter:UXANALYZE.FM_NOISEGDB |
Data channel | Select the data channel. Contains the list of data channels. If a Database is specified, a data channel selection is required. Script Parameter:UXANALYZE.FM_NOISE_DATA_CHAN |
Additive | Specify the additive value, which will increase/decrease the noise values from which will be added to the noise database. Default value is 0. Script Parameter:UXANALYZE.FM_ADITIVE |
Multiplier | Specify the multiplier, which will increase/decrease the noise values from the noise database. Default value is 1. Script Parameter:UXANALYZE.FM_MULTIPLIER |
Pick Origin | This button requires both the database and data channel to be entered. Clicking this button will display a map with a rendered grid based on the noise database and data channel selected. Click on the displayed map to specify the origin location. See the origin coordinates in the More/Less section below. |
IGRF (Mag) | |
Inclination | Specify the Inclination of the earth’s magnetic field. |
Declination | Specify the Declination of the earth’s magnetic field. |
Total Field | Specify the magnitude of the reference magnetic field. |
EM61 mk2 | |
Coil Size | Select the dimensions of the EM61 coils |
Mode | Select the EM61 measurement mode; D differential, 4 four time-gate. |
Gate | Select the time-gate to calculate for the forward model. |
Buttons | |
[Reset] | Clears all the entries in the target list. The Reset buttons are found on the Target Definition tab. |
[Colour Bar] | Opens the Colour Bar Extents dialog, enabling you to set the extents of the colour bar. The default is "Auto"; otherwise, you can choose "Manual" and specify the minimum and maximum extents for the data range for the colour bar. |
[Save] | Saves the forward model parameters to the output database. |
[Run] | Runs the forward model based on the parameters in the target list. It will create the output maps for the selected target. |
[Run Loop] | Runs the forward model based on the parameters in the target list. It will create the output maps for all the increments between the minimum and maximum. The various parameters will be plotted in separate groups in the same map. The groups can be cycled using the slider bar. Run Loop will only be enabled when TargetID, Parameter, Minimum, IncrementandMaximumhave values. Otherwise, it will be disabled and greyed out. |
[Invert] | Runs the fitting process to estimate the forward model parameters, and populates the Inverted column in target list with the inversion result. |
[More] |
|
Data chip size (metre) | Specify the data chip size, a square window over which the forward model will be calculated. Script Parameter:UXANALYZE.FM_DATA_CHIP_SIZE |
Origin X (metre) | Specify the X coordinate of the middle point of the target window. Default value is 0. If a background noise database is specified, the origin must be within the bounds of the background noise data. Script Parameter:UXANALYZE.FM_ORIGINX |
Origin Y (metre) | Specify the Y coordinate of the middle point of the target window. Default value is 0. If a background noise database is specified, the origin must be within the bounds of the background noise data. Script Parameter:UXANALYZE.FM_ORIGINY |
Line spacing (metre) | Specify the line spacing, which is used to create the grid points. Default value is 1. Script Parameter:UXANALYZE.FM_LINE_SPACING |
Sample spacing (metre) | Specify the sample spacing along the line, which is used to create the grid points. Default value is 0.1. Script Parameter:UXANALYZE.FM_SAMPLE_SPACING |
Azimuth angle (deg) | Specify the azimuth of the lines, which is used to create the grid points. Default value is 0. Script Parameter:UXANALYZE.FM_AZIMUTH |
Application Notes
When Forward Modelling is run for the first time, the "More" section at the bottom of the dialog will be displayed. This section defines the size of the data chip or ‘survey’ grid along with line and sample parameters, and it can be modified to suit your scenario as necessary. In subsequent runs, the dialog will remember the last state and will show or hide that section based on what you have decided.
The fields of a target parameters must either be all empty or contain a value. Run [Reset] to clear all the parameters for a target. At least one target must be fully specified.
To easily loop through a series of values for one of the targets parameters, in the "Parameter Loop" section select that target and the parameter. [Run Loop] will then automatically create a series of forward models that can be viewed by moving the slider.
Typical site or background noise can be included in your forward model. Selecting a background noise database will superimpose your forward model on the survey data. If a background noise database is selected, the origin location must be located within the extents of the background noise data. This can easily be done using the Pick Origin, which will generate a grid and map of the selected data channel.
The [Invert] option will invert the forwarded modeled data chip. This can be useful in helping understand the impact of overlapping anomalies or the background noise when inverting the anomaly data.
Munition List
The list of available munitions found in the Size parameter dropdown list is populated from a list generated empirically by AcornSI. The list defines Magnetic and EM61 parameters that are generated from inverting data collected over real-world items. For the magnetic response, the mag Size parameter is a scaled magnetic moment. For the EM61 response, there are several parameters: gate, time, and the three polarizabilities (or betas).
This list is stored in the "UxaForwardModelTable.xml" file, which can be found in the C:\Program Files\Geosoft\Desktop Applications \etc folder.
The following figure shows 20 MM M55 detailed information:
To add a new munition to the file, duplicate one of the <Munition>...</Munition> sections and modify the details to reflect the specifications of the new munition.
See Also:
Got a question? Visit the Seequent forums or Seequent support
© 2023 Seequent, The Bentley Subsurface Company
Privacy | Terms of Use