4.6.1 Destagger

Basic Description: Destagger shifts transects to correct for displacement errors, most often due to zig-zag survey, but also due to a lag in instrument recording. The problem is that entire transects are slightly off in their position and need to be shifted one way or another. The solution is to select the lines that should be moved and shift them to their correct location, and then fill in the gaps.
Technical Details: Destagger moves selected transects ("rows") by the stagger amount (in samples or pixels). If the fill gaps check box is checked, the gaps created from the line shifts will be filled in using the Fill Operation. If not, they are designated as NaN ("not a number").
Instructions: After choosing a selection method and making your selection on the survey, enter parameters in the following order (go to each section for details):
4.6.1 Destagger

Select Transects

1. Select Transects
Select which transects you woudl like to move:
All: If you select "All", then all transects will be shifted by the amount specified in the stagger amount box. For a zig-zag survey, then, all odd transects will shift in one direction and the evens in the other.
Even Only: If you select "Even Only", only the even numbered transects will shift. This way you can correct very minor shifts by moving only every other line by one pixel.
Odd Only: Same as above, only using odd line/transect numbers.

Select Shift Pattern

2. Select Shift Pattern
Most often you will leave this at 1. If you have data where lines 1-2 go in one direction, but lines 3-4 go in the opposite direction, for example, then you can enter two hear and they will be treated as one line and shifted together.

Stagger Amount

3. Stagger Amount
Enter a value for the number of samples or pixels to shift the lines/transects. Use a positive number to shift lines forward in the direction of survey, or negative for shifting them backwards relative to the direction of survey.

Fill Gaps

4. Fill Gaps
Check this box to fill in the gaps created from the shifting of lines. The Fill Operation will be used. If you would rather leave these areas blank, do not check this box. You can also leave this box unchecked, but use the Fill Operation separately.
Last Updated June 15, 2011