to compute a DTM of the averaged computed depth
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HowTo Combine Depths Z
  • -CZ/tanzaniaCZ/25_0_0_0/McSTD3.0_N3/1670_2540/524415_9098385/1_1      
  • This replaces the -dB... argument.
  • It specifies
    • the database.pix to be created :here tanzaniaCZ.pix with
      • number of channels: here 25 U8 channels
    • Georeferencing
      • UTM coordinates of center of georeferencing pixel: here 1670_2540/524415_9098385
      • image coordinates of georeferencing pixel: here 1_1
    • Averaging depths
      • M(m)
        • M to process all images, from MakePIX... to Model...
        • m to skip processing of all images
      • cSTD:  a coefficient for restricting the array of available depths
      • N: the minimum number of depth results to allow computation of an average depth
  • database.pix 
    • shall first receive
      • a copy of channel_Z250 of nbPIX images of the series:
      • that's nbPIX channels from channel_1 to channel_nbPIX=12 for the twelve images of the Tanzania series
    • then shall receive
      • channel_nbPIX+1=13: sequential number of the image that yielded the deepest depth
      • channel_nbPIX+2=14: deepest depth
      • channel_nbPIX+3=15: number of depths that were used for computing an average depth
      • channel_nbPIX+4=16: standard deviation on average computed depth
      • channel_nbPIX+5=17: average depth


How to combine depths from a series of images
  • to produce an image of the deepest depths
  • to produce an image of the average depth
"I think we should easily be able to do the data combination to obtain deepest values.   
Clearly the quality of the result will depend on what 4SM is able to produce.   
Currently I am unclear how sediment, even if very slight, affects the results. 
I was hoping multi-date images might illustrate the capabilities or limitations.
Example for a 12 TM/ETM images series
Original dataa time series of 12 co-registered images must be available, 

with the same number of lines and columns, superposable
  • All 12 4-bands BGRN Landsat TM or ETM original images in format image.pix must be placed in the same directory
    • and each image shall have a directory with its name
First, Model all images, each in its directory
  • All images shall be calibrated and modeled in their respective directories, using their respective 4SM commandline
    • -MakePIX..., -Import..., -Extract..., -Calibrate..., -Model...
then Combine depth results: run script in main directory
  • Once all images are modeled to the best of your satisfaction in their respetive directories, prepare a commandline script in the main directory, and execute it: it shall
    • prepare a list all images.pix available
    • create a tanzaniaCZ.pix image with all specified U8 channels
    • import Computed depths from channel_Z250 of each modeled image
nice -20 ./4SM.2.06 -PROCESS/24_FEB_2009/MASK_0 -Origin/NPA-FUGRO       
@-DN1530/54 @-DN1350/270
Average depth
  • The practitioner may modify
    • N, the minimum number of depth results required to compute an average depth
    • cSTD, the coefficient that is applied to the standard deviation for restricting depth range using the filter:
      • avZ-stdZ/cSTD=depth<=avZ+stdZ/cSTD
    • In practice, 4SM first computes an average for all depths available: average+-standard_deviation (N=N), then
      • if the condition on N is satisfied, 4SM rejects those depths that fall outside the specified range and computes a new depth and standard deviation which is written out
        • if N is found to be less than 2, no average depth is written out
      • else the first result is written out
    • As of 09 march 2009, this is only very rough, and needs to be improved
      • still, the result is quite interesting and promising.

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