Dynamic Background Correction

PDF Download

Summary

This page describes how to background correct dynamic data using estimates from a polygon area.

Procedure

A flow can be run to remove the BG so you can visualize the BG removed data.

1. Create a BG cell on the unfiltered data state. Load up the SU, and select an unfiltered grid indicator like the “z.z” indicator (used in this example). Then zoom into a suitable BG location. Once you have the location you want, right click on the grid view and select “Create Background Cell” as shown here:

   

   Then mouse down and drag out to create the BG cell :

   

   Release the mouse, and it will say this:

   

   If you want, you can see the newly created BG cell in the cell list. You can show the cell list like this:

   

   The bg cell is in red text to indicate that it’s the Active BG cell…….so it will be used in any BG subtraction operation.

2. Create a flow. Go to the Proc tab and select the M,SU Flow2 (because it’s probably not getting used for anything right now…….you could select the M,SU Flow3 ……doesn’t matter). In the flow, add a Subtract BG function and configure it like this:

   

   Once that’s done, mouse down on the Subtract BG step in the flow, and drag it over to the Grid indicator bar. The configure it like this (for example):

   

   You can also drag it over to the Profile View. Now you can run the flow, and visualize the results.

   Note: A ‘Raw to Merged’ step is not needed if the data has already been merged.   If there is no ‘Raw to Merged’ function in the flow, then all functions in the flow will automatically operate on the Merged data. So the background will just get subtracted from the unfiltered merged data. Now if we did put in a Raw to Merged function, we could insert a Subtract BG function above it, so the background would get subtracted from the Raw data before everything gets merged. An important result is the other data states would get overwritten and the demedian results would not be available for comparison.

3. If you want to invert on the BG removed datastate -b, then create a new inversion configuration that uses unfilt datastate for the “In” parameter (because when you invert, it will automatically grab the active BG and subtract it before it inverts.

   NOTE: You can have multiple BG in SU.

   Before you invert, just make sure you have the BG cell you want. So right click and “Set as Background”, like this:

   

   That will make it the Active BG, which will continue to get used by any subsequent inversions (until you want to change the BG again).