[GRASSLIST:3614] very low fp values problem

[Maciek Sieczka]

hello fellow grassies!

I'm trying to reduce vignetting on my aerial photos and luckily I'm
approaching some results. By the way a strange thing occured when working
with rasters with very low floating point values.

if fixed already in 5.3 or please let me know and sorry for bugging!

the problematic raster's name is 'kor_lx'
detailed description is at the bottom and a screendump is attached

the issue step by step:

    r.info -r kor_lx
    min=0.000000
    max=0.000000

but I wanted to know the exact values so I tried:

    r.univar kor_lx

    This module calculates univariate statistics...
    Calculation for full image kor_lx at vignet...
    (no base mask map set, ignoring NULL cells)
    Reading raster map...
    r.stats:  100%
    Calculating statistics...

but it failed:

    Number of cells (excluding NULL cells): 3407232
    Minimum: 0
    Maximum: 0
    Range:  0
    Arithmetic mean:  0
    Variance:  0
    Standard deviation: 0
    awk: cmd. line:17: (FILENAME=- FNR=3407232) fatal: division by zero
    attempted

and when run interactively:

    r.univar

    Enter base raster map (or return to skip)
    Enter 'list' for a list of existing raster files
    Hit RETURN to cancel request
    > kor_lx
    <kor_lx>
    kor_lx at vignet

    Enter cover raster map
    Enter 'list' for a list of existing raster files
    Hit RETURN to cancel request
    > kor_lx
    <kor_lx>
    kor_lx at vignet

    This module calculates univariate statistics...
    Calculation for images kor_lx at vignet masked through kor_lx at vignet...
    (ignoring NULL cells)
    Reading raster maps...
    r.stats:  100%

    ERROR: Map kor_lx contains only NULL data in current region.

so I tried copying the map category values to their grey scale equivalents:

    r.mapcalc 'kor256=#kor_lx'
     100%

and strange here the strange is that the max value is not 255 as it should:

    r.info -r kor256
    min=0
    max=254



GRASS:~ > r.info kor_lx

+---------------------------------------------------------------------------
 | Layer:    kor_lx                         Date: Mon Jun  7 19:31:56 2004
 | Mapset:   vignet                         Login of Creator: ziutek
 | Location: kpn92
 | DataBase: /home/grassdata
 | Title:     ( kor_lx )
|---------------------------------------------------------------------------
 |   Type of Map:  cell                Number of Categories: 255
 |   Data Type:    DCELL
 |   Rows:         1824
 |   Columns:      1868
 |   Total Cells:  3407232
 |        Projection: x,y (zone 0)
 |            N:       1824    S:          0   Res:     1
 |            E:       1868    W:          0   Res:     1
 |   Range of data:    min =  0.000000 max = 0.000000
 |   Data Source:
 |   Data Description:
 |    generated by r.mapcalc
 |   Comments:
 |    (1218.010000 / (sqrt((x() - 941.000000) ^ 2.000000 + (y() -
 |    928.000000) ^ 2.000000) ^ 2.000000 + 1218.010000 ^ 2.000000)) ^
 |    4.500000
+---------------------------------------------------------------------------
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