Your first experience at Tarawa atoll, Kiribati
Activity
nothing to do for now, just read below
 
Raw data
  • raw data is in /data/tarawa-full.tif 
    • use OpenEV to export it to /data/tarawa-full.pix


Georeferencing
  • the -MakePIX/.... procedure takes its georeferencing from 
    • the -dB/...........argument
    • the -Mis/..........argument
    • the -Import/.... argument
  • the shapefiles need to be prepared over a backdrop image which is properly georeferenced.
Shapefiles
  • OpenEV only writes 
    • .shp, .dbf and .shx
  • 4SM calls up shp2text in order to
    • read the shapefile
    • write a SHP.txt textfile
    • then proceed to use it as appropriate for
      • working out the geometry and georeferencing of the image subset
      • querrying a pixel
      • modeling a pixel
      • profiling : dynamic memory allocation allows for very long profiles
      • recoding of ROI in mask_SE
      • sampling of ROI
      • you name it!!!

working database tarawa-subset.pix
Get acquainted with its 28 channels
-DB/.../27_1_0_0/...
 1_U8_Raw_550 nm
 2_
U8_Raw_650 nm
 3_U8_Raw_850 nm
 4_U8 Special_Effect_mask; use pctmSE
 5_U8 wZ: use pctwZ
 6_U8 wR: use pctwR
 7_U8 Z0->250 in dm: use pctZ250
 8_U8 Z: use pctZ20
 9_U8 B: use pctB
10_U8 Bottom Typing: use pctClassified
11_U8 LSBCC_blue 
12_U8 LSBCC_green
13_U8 LSBCC_red  
14_U8 dZED: use pctZ250
15_U8 BPL_12  15
16_U8 BPL_13  16
17_U8 BPL_23  17
18_U8 void18
19_U8 void19
20_U8 void20
21_U8 void21
22_1_U8_Deglinted_Green
23_2_U8_Deglinted_Red
24_3_U8_Deglinted_NIR
25_1_U8_WaterColumnCorrected_Green
26_2_U8
_WaterColumnCorrected_Red
27_3_U8_WaterColumnCorrected_NIR
28_S16_ZG_Zretrieved in centimeters

working database tarawa-subset.pix
Get acquainted with its future content
 
  • No worries with this:
  • 4SM shall complain if you do not specify enough channels
    • And it does not hurt if you have more than enough.


The thing is:
For a N bands 16 bits raw image, you need 
  • N*U16 bands for raw 16U data
  • N*U8 bands for U8 scaled raw data
  • N*U8 bands for deglinted data
  • N*U8 bands for water column corrected data
  • Plus at least 14 U8 channels for various uses
That is at least 4*N + 14.



For a 3 bands U8 SPOT image,
  • that is at least 4*3+14=26 U8 channels
For a 4 bands U8 Landsat TM image
  • that is at least 4*4+14=30 U8 channels
For a 6 bands U16 Landsat  8 image
  • that is at least 4*6+14=38 U8 channels
 
channels 1, 2, 3
   
Tarawa-subset_Raw_Image 
a spectral raw image subset, heavily glinted.
OpenEV pseudo-color pallets=====>>>>>
They are located in ./4sm.calls/pct=====>>>>>

channel_4 
Tarawa-subset_mSE


this is the special effects mask

 
 
  • Blue:...........mSE=2 over open waters
  • Orange:.......mSE=3 in the lagoon
  • Red:.............mSE=4 in the lagoon
  • Brown:.........mSE=248 for lands areas
Please note that, over the orange area, 
 the higher foreshore is exposed,
therefore mapped as land 

 

channel_5   
Tarawa-subset_WZ 

with following codes 
  • Grey...........for clouds
  • Brown........for dryland
  • Dark Blue..for wZ=240: optically deep pixels
  • Blue............for WZ=1 where Depth is computed using Lbref[1] and band_1 alone
    • the ONE-BAND solution
  • Green.........for WZ=2 where Depths are computed using both band_1 and band_2
    • the RED solution
  • Red........... for WZ=3 where Depths were computed using band_1, band_2 and band_3 
    • the NIR solution

channel_6   
Tarawa-subset_WR  
Smoothing Window Radius (kernel)

with following codes 
  • Black          No_smoothing on land, clouds, etc
  • Green         Radius=5......average of 81 pixels
  • Light Blue   Radius=4......average of ... pixels
  • Red             Radius=3......average of ... pixels
  • Yellow        Radius=2......average of 9 pixels
  • Pink            Radius=1......average of 5 pixels
 
channel_7   
Tarawa-subset_Z250  
Depths in decimeters, range 1-250 

with following codes 
  • Yellow   for non-marine areas
  • Shades of blue for depths  up to 25 meters
  • Deep blue for optically deep areas
 
channel_8   
Tarawa-subset_Z20  

Depths in decimeters
coded for screen display
  
of no interest here as the depth does not exceed 25 m
  • Yellow   for non-marine areas
  • Shades of blue then green for depths from 1 meter up to 25 meters
  • Pale green for optically deep waters


 
 
channel_9   
Tarawa-subset_B  
Average Bottom Reflectance  

 is scaled from 0 to 200
 
 

 
....
 
channel_10
Bottom typing

not in use with SPOT XS images
.... channels 11, 12, 13, 14
are of no interest for a SPOT XS image

channels 15, 16, 17
  • channel 15 exhibits BPL pixels for the pair 1/2, i.e. for the Green vs Red pair
  • channel 16 exhibits BPL pixels for the pair 1/3 i.e. for the Green vs NIR pair
  • channel 17 exhibits BPL pixels for the pair 2/3 i.e. for the Red vs NIR pair
They are displayed here as a color composite
 
.........
 
channels 18, 19, 20, 21
are void ,  available for future use
 
channels 22, 23, 24  

contain the smoothed/deglinted image  
Tarawa-subset_Smoothed_Deglinted 

a spectral image in NATURAL radiances,
HistEq enhancement

using -E.shp shapefile,
subwindow -E100/550/200/400
is not deglinted.


 
 
channels 25, 26, 2727
  
contain the water column corrected reflectance  
Tarawa-subset_Spectral_Bottom_Reflectance
 

A spectral image, scaled from 0 to 250.
Of no interest for an image without a Blue band. 
 


 

channel_28   
Tarawa-subset_Z_in_centimeters 


Of no interest here
as depths do not exceed 15-20 m 
inside the lagoon. 

But this channel is used 
upon seatruthing

 
 
return to tarawa-tutorial     next to Prepare your image



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