[GRASS-dev] [GRASS GIS] #1687: i.atcorr return NULL values

[GRASS GIS]

#1687: i.atcorr return NULL values
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 Reporter:  curvelo  |       Owner:  grass-dev@…              
     Type:  defect   |      Status:  new                      
 Priority:  normal   |   Milestone:  6.4.3                    
Component:  Imagery  |     Version:  6.4.2                    
 Keywords:           |    Platform:  MSWindows Vista          
      Cpu:  x86-64   |  
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Changes (by gisix):

 * cc: gisix (added)


Comment:

 Hi,

 i.atcor produces NULLs and strange output also for other sensors:
 I can confirm this for RapidEye data:
 Input Data: L3A RapidEye data without notable clouds and no blackfill.
 Bands used: bed / green / blue

 As RapidEye data comes in 16bit, the input data was initially rescaled to
 8bit [0-255]. The results were unexpected: Only three category values:
 Many zeroes and a few "1" and "2" values. This applied for all three
 bands.

 In a next attempt, the original 16bit data was fed into i.atcorr. The
 results are described below. This was compared with a shifting (r.rescale)
 of the 16 bit value ranges of all bands to start with the value "0"
 [Example: original range: [4068-56975] (range: 52907) -> new range: [0 -
 52907]]. The results from both kinds of input are similar:

 **For the red band, a reasonable result was produced.**
 Statistics of red band (digital numbers) [r.univar]:
 n=49000000
 null_cells=25249370
 cells=74249370
 min=1286
 max=58603
 range=57317
 mean=4733.57011167347
 mean_of_abs=4733.57011167347
 stddev=1226.24474903503
 variance=1503676.18453598
 coeff_var=25.905283329616
 sum=231944935472

 ** For the green band, a NULL layer was produced. **

 Statistics of green band (digital numbers) [r.univar]:
 n=49000000
 null_cells=25249370
 cells=74249370
 min=2464
 max=54248
 range=51784
 mean=5646.62104434694
 mean_of_abs=5646.62104434694
 stddev=986.535495533873
 variance=973252.283948265
 coeff_var=17.471253831024
 sum=276684431173


 ** For the blue band, faulty values (looked like a binary image of the
 original scene) were produced. **

 Statistics of blue band (digital numbers) [r.univar]:
 n=49000000
 null_cells=25249370
 cells=74249370
 min=4068
 max=56975
 range=52907
 mean=6479.12217332653
 mean_of_abs=6479.12217332653
 stddev=859.459951841108
 variance=738671.408818719
 coeff_var=13.2650678417419
 sum=317476986493

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Ticket URL: <http://trac.osgeo.org/grass/ticket/1687#comment:2>
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