r.hazard.flood error output

[zimbogisgeek]

Running r.hazard.flood produces an erroneous map mainly because in the r.hazard.py script there is a mistake in calculating the final map. The command that produces the error is

grass.mapcalc("$r_flood_map = $rast1 / $rast1", r_flood_map = r_flood_map, rast1 = 'r_flood_th')

which should be

grass.mapcalc("$r_flood_map = $rast1 / $rast2", r_flood_map = r_flood_map, rast1 = 'r_flood_th', rast2 = 'r_flood')

[madi]

Hi, thank you for pointing this out, but does this actually produce an erroneous result? could you give an example? Thanks

[lucadelu]

Hi Madi, but the code is dividing the same maps

"$r_flood_map = $rast1 / $rast1"

so it return for every pixel 1, is it the right behavior?

[madi]

Replying to lucadelu:

Hi Madi, but the code is dividing the same maps

"$r_flood_map = $rast1 / $rast1"

so it return for every pixel 1, is it the right behavior?

yes, the expected result is a binary map (yes=1, no=null) Thanks, madi

[neteler]

Replying to madi:

Replying to lucadelu:

Hi Madi, but the code is dividing the same maps

"$r_flood_map = $rast1 / $rast1"

so it return for every pixel 1, is it the right behavior?

The behaviour in question comes from r.mapcalc:

yes, the expected result is a binary map (yes=1, no=null)

Here a quick test:

r.mapcalc "result = 1/1"
r.univar -g result | grep 'min\|max\|null'
null_cells=0
min=1
max=1

r.mapcalc "result2 = 0/0"
r.info result2 | grep 'min\|max\|null'
 |   Range of data:    min = NULL  max = NULL

r.mapcalc "result3 = null()/null()"
r.info result3 | grep 'min\|max\|null'
 |   Range of data:    min = NULL  max = NULL

Is this what should happen in r.hazard.flood?

[madi]

Replying to neteler:

Replying to madi:

Replying to lucadelu:

Hi Madi, but the code is dividing the same maps

"$r_flood_map = $rast1 / $rast1"

so it return for every pixel 1, is it the right behavior?

The behaviour in question comes from r.mapcalc:

yes, the expected result is a binary map (yes=1, no=null)

Here a quick test:

r.mapcalc "result = 1/1"
r.univar -g result | grep 'min\|max\|null'
null_cells=0
min=1
max=1

r.mapcalc "result2 = 0/0"
r.info result2 | grep 'min\|max\|null'
 |   Range of data:    min = NULL  max = NULL

r.mapcalc "result3 = null()/null()"
r.info result3 | grep 'min\|max\|null'
 |   Range of data:    min = NULL  max = NULL

Is this what should happen in r.hazard.flood?

Precisely so.

[madi]

I double checked the code and unless I can't see the obvious it looks alright to me. Therefore I'm closing this ticket as invalid. Please feel free to reopen it if something looks amiss. However, the expected result of this tool is indeed a binary map.