[GRASS-user] Comparing 2 large Corine Land Cover maps

[S. Koukoulas]

try
r.cross (Raster>Overlay Rasters>Cross product) for a
cross-classification map
and
r.coin (Raster>Reports and Statistics>Mutual category occurrences) for
cross tabulation
also r.kappa (Imagery>Reports and statistics>Kappa Analysis) for a
comparison

cheers,
s.

On 07/22/2011 01:41 PM, Hermann Peifer wrote:
> Hi,
>
> I have 2 Corine Land Cover (CLC) raster maps, from 2000 and 2006. Both
> maps have the same extent, the same resolution (100m) and use the same
> 44 CLC categories. The maps are pretty large: 67 000 cols x 58 000
> rows = 3 886 000 000 cells.
>
> I'd like to categorise the changes between the 2 layers, according to
> a decision matrix which I pasted below [1]. Row headers indicate the
> clc2000 category, column headers represent the clc2006 category. I
> only pasted the "left half" of the table in order to avoid ugly line
> breaks.
>
>
> Question:
> Is there a better (and faster) way than doing this comparison by using
> r.mapcalc with a (nearly) endless if/else chain [2] ?
>
> I also noted that in 99+ % of the cases, both maps are NULL or have an
> identical CLC category, so I wouldn't need the if/else chain at all. I
> guess I can use this fact to shortcut the comparison?
>
>
> Thanks in advance, Hermann
> (using GRASS 6.4 on 64-bit Debian Linux)
>
> [1]
>
> ##  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 ..
>  1 NA 12 31 32 33 34 35 36 37 13 38 56 56 56 56 56 56 56 56 56 56 56 ..
>  2 11 NA 31 32 33 34 35 36 37 13 38 56 56 56 56 56 56 56 56 56 56 56 ..
>  3 12 12 NA 32 33 34 35 36 37 13 38 56 56 56 56 56 56 56 56 56 56 56 ..
>  4 12 12 31 NA 33 34 35 36 37 13 38 56 56 56 56 56 56 56 56 56 56 56 ..
>  5 12 12 31 32 NA 34 35 36 37 13 38 56 56 56 56 56 56 56 56 56 56 56 ..
>  6 12 12 31 32 33 NA 35 36 37 13 38 56 56 56 56 56 56 56 56 56 56 56 ..
>  7 12 12 31 32 33 34 NA 36 37 13 38 56 56 56 56 56 56 56 56 56 56 56 ..
>  8 12 12 31 32 33 34 35 NA 37 13 38 56 56 56 56 56 56 56 56 56 56 56 ..
>  9 12 12 31 32 33 34 35 36 NA 13 38 56 56 56 56 56 56 56 56 56 56 56 ..
> 10 11 11 31 32 33 34 35 36 37 NA 38 56 56 56 56 56 56 56 56 56 56 56 ..
> 11 11 11 31 32 33 34 35 36 37 13 NA 56 56 56 56 56 56 56 56 56 56 56 ..
> 12 21 22 31 32 33 34 35 36 37 13 38 NA 45 43 42 42 42 41 42 41 83 61 ..
> 13 21 22 31 32 33 34 35 36 37 13 38 43 NA 43 42 42 42 41 42 41 83 61 ..
> 14 21 22 31 32 33 34 35 36 37 13 38 43 43 NA 42 42 42 41 42 41 83 61 ..
> 15 21 22 31 32 33 34 35 36 37 13 38 45 45 45 NA 44 44 41 45 45 83 61 ..
> 16 21 22 31 32 33 34 35 36 37 13 38 45 45 45 44 NA 44 41 45 45 83 61 ..
> 17 21 22 31 32 33 34 35 36 37 13 38 45 45 45 44 44 NA 41 45 45 83 61 ..
> 18 21 22 31 32 33 34 35 36 37 13 38 45 45 45 42 42 42 NA 45 45 83 61 ..
> 19 21 22 31 32 33 34 35 36 37 13 38 45 45 45 42 42 42 41 NA 41 83 61 ..
> 20 21 22 31 32 33 34 35 36 37 13 38 45 45 45 42 42 42 41 45 NA 83 61 ..
> 21 21 22 31 32 33 34 35 36 37 13 38 52 52 52 52 52 52 41 52 54 NA 54 ..
> 22 21 22 31 32 33 34 35 36 37 13 38 45 45 45 42 42 42 41 45 45 83 NA ..
> 23 21 22 31 32 33 34 35 36 37 13 38 51 51 51 51 51 51 53 51 53 53 53 ..
> 24 21 22 31 32 33 34 35 36 37 13 38 51 51 51 51 51 51 53 51 53 53 53 ..
> 25 21 22 31 32 33 34 35 36 37 13 38 51 51 51 51 51 51 53 51 53 53 53 ..
> 26 21 22 31 32 33 34 35 36 37 13 38 52 52 52 52 52 52 54 52 54 54 54 ..
> 27 21 22 31 32 33 34 35 36 37 13 38 52 52 52 52 52 52 54 52 54 54 54 ..
> 28 21 22 31 32 33 34 35 36 37 13 38 52 52 52 52 52 52 54 52 54 54 54 ..
> 29 21 22 31 32 33 34 35 36 37 13 38 52 52 52 52 52 52 54 52 54 54 54 ..
> 30 21 22 31 32 33 34 35 36 37 13 38 52 52 52 52 52 52 54 52 54 54 53 ..
> 31 21 22 31 32 33 34 35 36 37 13 38 52 52 52 52 52 52 54 52 54 54 53 ..
> 32 21 22 31 32 33 34 35 36 37 13 38 52 52 52 52 52 52 54 52 54 54 53 ..
> 33 21 22 31 32 33 34 35 36 37 13 38 52 52 52 52 52 52 54 52 54 54 53 ..
> 34 NA NA NA NA NA NA NA NA NA NA 38 NA NA NA NA NA NA NA NA NA NA NA ..
> 35 21 22 31 32 33 34 35 36 37 13 38 55 55 55 55 55 55 55 55 55 55 55 ..
> 36 21 22 31 32 33 34 35 36 37 13 38 55 55 55 55 55 55 55 55 55 55 55 ..
> 37 21 22 31 32 33 34 35 36 37 13 38 55 55 55 55 55 55 55 55 55 55 55 ..
> 38 21 22 31 32 33 34 35 36 37 13 38 55 55 55 55 55 55 55 55 55 55 55 ..
> 39 21 22 31 32 33 34 35 36 37 13 38 55 55 55 55 55 55 55 55 55 55 55 ..
> 40 21 22 31 32 33 34 35 36 37 13 38 55 55 55 55 55 55 55 55 55 55 55 ..
> 41 21 22 31 32 33 34 35 36 37 13 38 55 55 55 55 55 55 55 55 55 55 55 ..
> 42 21 22 31 32 33 34 35 36 37 13 38 55 55 55 55 55 55 55 55 55 55 55 ..
> 43 21 22 31 32 33 34 35 36 37 13 38 55 55 55 55 55 55 55 55 55 55 55 ..
> 44 21 22 31 32 33 34 35 36 37 13 38 55 55 55 55 55 55 55 55 55 55 55 ..
>
>
> [2]
>
> change = \
> clc2000 == 1 && clc2006 == 2 ? 12 : \
> clc2000 == 1 && clc2006 == 3 ? 31 : \
> clc2000 == 1 && clc2006 == 4 ? 32 : \
> clc2000 == 1 && clc2006 == 5 ? 33 : \
> clc2000 == 1 && clc2006 == 6 ? 34 : \
> clc2000 == 1 && clc2006 == 7 ? 35 : \
> clc2000 == 1 && clc2006 == 8 ? 36 : \
> clc2000 == 1 && clc2006 == 9 ? 37 : \
> clc2000 == 1 && clc2006 == 10 ? 13 : \
>
> ... (snip away some 1700 if/else rules)
>
> clc2000 == 44 && clc2006 == 30 ? 89 : \
> clc2000 == 44 && clc2006 == 31 ? 89 : \
> clc2000 == 44 && clc2006 == 32 ? 89 : \
> clc2000 == 44 && clc2006 == 35 ? 82 : \
> clc2000 == 44 && clc2006 == 36 ? 82 : \
> clc2000 == 44 && clc2006 == 37 ? 82 : \
> clc2000 == 44 && clc2006 == 38 ? 89 : \
> clc2000 == 44 && clc2006 == 39 ? 89 : \
> clc2000 == 44 && clc2006 == 42 ? 82 : \
> clc2000 == 44 && clc2006 == 43 ? 82 : 0
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