tarawa tutorial : Prepare your image (1)
the AutoCAL process in 4SM
now takes care of almost everything for you

to Tarawa tutorial       
to Prepare your image       continued
to Deglint and investigate your image
to Extract calibration data
to Calibrate under Mask=4
to Modeling under Mask=4
to Calibrate whole lagoon
to Modeling the whole lagoon

  back   next

1 - NO NEED for field data, nor for atmospheric correction
2 - this is demonstrated in this website, using a variety of hyper/multi spectral data
Requirements are
1 - homogeneous water body and atmosphere
2 - some coverage of optically deep water
3 - some coverage of dry land
Problems are
1 - the precision on estimated depth is found wanting, because the noise-equivalent change in radiance  of accessible data is too high for shallow water column correction work 
2 - radiance data should be preprocessed by the provider at level 1 in order to improve S/N ratio
3 - exponential decay: the deeper/darker the bottom, the poorer the performances
I keep digging
until suitable data
become available

Browser for tutorial
please have FireFox available when using 4SM.4.08 version

Prepare your image
step 1: prepare shapefiles
step 2: learn about PCIDSK database structure: create tarawa-subser.pix
step 3: the 4SM command line
step 4: the AutoCAL script
Compute glint regressions
Write the special effects mask in channel 4
Extract the calibration data text file
Perform an automatic calibration
Display a preliminary calibration diagram
Write the 4sm.def defaults file
Write and display the 4SM command line for the next step
step 6: about the segmentation of the image
step 7: things you can do
next to Deglint-and-Investigate-your-image

step 1 - Prepare Shapefiles
  • export tif file to PCIDSK file
  • display PCIDSK file in Openev
  • draw shapefiles
Your work directory should look like this

Raw data is in data/tarawa-full.tif
The raw data image is to be stored as Tarawa/data/tarawa-full.tif

Use OpenEV to
  1. export tarawa-full.tif into tarawa-full.pix in PCIDSK format
  2. use the tarawa-full.opf project to display a FCC of tarawa-full.pix 
  3. draw a rectangular polygon shapefile to specify your area of interest
  4. save it in your work directory as ../import.shp
    1. import.shp IS PROVIDED,

Now you need to draw several shapefiles inside your import area
and save them in the work directory,
ready for use in the AutoCAL process


Red : mask_3

Blue : mask_4

LightBlue : glint

Purple : Lsw

Orange : LsM

Green : vegetation

White : import

step 2 - Learn about PCIDSK database structure
  • get acquainted with working PCIDSK database.pix file structure
    • so that you'll know what 4SM shall do when running the AutoCal process
The PCIDSK file structure is specified in the -DB... commandline argument
  • -DB/tarawa-subset/27_1_0_0/3_1/650_600/718.079_169.221/1_1
    • U8=27
    • S16=1
    • U16=0
    • R32=0
    • bands=3
    • FirstChRaw=1
    • nbRow=650
    • nbLin=600
    • X0UTM=718.079
    • Y0UTM=169.221
    • Georeferencing pixel: UL pixel: Row_1 and Lin_1
  • Here you get acquainted with the PCIDSK file structure for working database Tarawa/tarawa-subset.pix
  • PCIDSK database.pix file can have one of three interleaving structures
    • file : you get one header file named database.pix and N channels named database.001 to database.00N
      • fast to access for read/write,
      • handy for replacing any channel by a blank one (except for raw data channels)
      • handy for archiving (just erase all channels but the raw data, then compress)
    • band: you get one database.pix file, starting with the header, then with channel 1, then channel 2, etc, all the way to channel N
    • pixel: you get one database.pix file, starting with the header, then spectral pixel 1, then spectral pixel 2, all the way to last pixel : slowest to access for read/write
  • By default, 4SM uses the FILE interleaving
    • file   Tarawa/tarawa-subset.pix is the header: an ASCII text file
      • you can print it on your session screen:
        • "more tarawa-subset.pix"
        • "tail tarawa-subset.pix"
    • files tarawa-subset.001 to file tarawa-subset.028 are binary files
      • you can't print them on your session screen
      • "more tarawa-subset.001"
      • these are 650*600, U8, S16, U16 or R32
      • you can open any of them separately in OpenEV using File Open Raw
Database structure:    dbnc    for "database number of channels" in PCI parlance
  • Header, contains metadata, list of channels with channel descriptors, georeferencing, pseudo-color tables
  • U8 channels:
    • Landsat TM raw data are stocked as channels 1 to 4
    • Ikonos U8-scaled raw data are stocked as channels 1 to 4
    • SPOT1 raw data U8 are stocked as channels 1 to 3
  • S16 channels: imageG in centimeters is stocked there
  • U16 channels:
    • Landsat 8, WorldView2, Ikonos 4 raw data channels are stocked there
  • R32 channels: 4SM does not use real 32bits channels
and the expected
are now available.

In step 3, we shall create the working database 4sm_tutorial_tarawa/data/tarawa-full.pix
Database structure is dbnc=27,1 ,0 ,0
FILE interleaving is most handy
  • Interleaving: FILE : this is the default : keep to it
  • upon execution of 4SM, any missing file is re-created
for "modify channel description" in PCI parlance
Upon creation of the database /Tarawa/tarawa-subset.pix at step 3,
4SM shall write a channel and pseudocolor pallet description
which may be found in textfile tarawa-subset.mcd


Learn about the special effect mask mSE
Upon creation of the database /Tarawa/tarawa-subset.pix at step 3,
4SM shall write a special effect mask in channel 4


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