Manual Processing Of AEM Data

The purpose of the manual processing of AEM data is to make a visual inspection of the data and make edits to the Automatic processing. Manual processing of AEM data is done in the AEM Edit Form (EditFormAEM), which consists of a number of collections, series (subclass of collections) and plot forms. To open the AEM Edit Form select the processing node that should be edited and click Show and Edit on the Data Processing ribbon.

Manual AEM processing is memory based. To save the processing to the database press the Save Processed data to GERDA database button. To reduce memory usage data are loaded into the memory in buffers (intervals). The buffer is specified in the Buffer Size And Position (BufferSizeAndPosition) window, which is accessible through the AEM Edit Form. The helicopter position is highlighted on the GIS map.

If Find Nearest is selected from the GIS ribbon and used on the GIS map, any opended processing AEM Edit Form automatically centers on the position nearest to clicked location on the GIS map.

Altitude Data Processing

Manual altitude processing is done by creating new Altitude User Edits series for each segment of the processing that needs to be corrected.

First select the Altitude User Edit collection, then press the Add New Series to selected Collection button to create a new Altitude User Edit series. Next while the Altitude User Edit collection is selected, set to be visible, and the new Altitude User Edit series is highlighted, press the Draw Series in Chart button from the Chart Tools (ChartTools). Now the new series can be drawn directly on the Edit Form. Since these corrections are first applied when update button is used, it is recommended to do so before moving the buffer window along. To remove an Altitude User Edit series again use the Delete Selected Series button.

Note that any hightlighted Altitude User Edits series can be extended, also one that is far away from the current buffer size, so make sure to be drawing to a new series when making a new Altitude User Edit.

Voltage Data Processing

To assist in the AEM voltage data processing Sounding Plots showing the data curves as magnetic decay, dB/dt, or apparent resistivity, rhoa, are available. Data can be shown as either raw or average series. Distinct soundings can be selected via the Sounding Positions plot in the top of the AEM Edit Form or the Sounding List, which must be open during processing for all functionalities to work properly.

Coupled data must be removed from the raw data series before evaluating the average series. After removing coupled data it is necessary to run the averaging again by pressing the Update button. Selector tools are available from the Chart Tools. Data points can be toggled on/off or user defined uncertainty added. The total uncertainty of any data point is a function of the uniform uncertainty, an uncertainty based on the stack and the user defined uncertainty:
 

STD_total=(STD_uniform²+STD_stack²+STD_user²)^1/2 

The STD_stack contribution depends on the data type. For SkyTEM data imported from skb files, raw gates now include an STD that allows the STD_stack to more correctly reflect the noise in the data. Previously and for all other airborne data types, the raw gates do not have an STD value and the STD_stack instead reflect how spread out the raw data is.

When the processing is finished data can be inverted.

Plotting Data From TEM Files

It is possible to use the Sounding Curve plots of the AEM processing system to show data from tem files. To do this open a Sounding Curve plot, right-click on the plot and select Open Chart File. Point to the file you wish to display and hit OK. The chart sets the axis automatically (dB/dt or rhoa) to fit the data file format. The plot has a “Hold On” function, i.e. more data files can be shown in the data plot by selecting multiple files simultaneously or by opening new tem files in a chart that already contains one or more of these. To clear the chart the plot form must be closed.