Hei,

Before investing time in getting r.terraflow to work on larger regions I actually tried r.fill.dir.

The problem is that the results are significantly different and those of r.terraflow and r.hydrodem (where no breaching is performed) are more suitable for my needs. Here, r.terraflow fills most, r.fill.dir least and r.hydrodem inbetween.

Here a little comparison based on NC data:

g.extension extension=r.hydrodem operation=add

g.region -p raster=elevation

r.fill.dir --overwrite --verbose input=elevation output=elevation_fill_dir_depressionless direction=elevation_fill_dir_direction areas=elevation_fill_dir_pas

r.hydrodem -a --overwrite input=elevation memory=5000 output=elevation_hydrodem_depressionless

r.terraflow --overwrite --verbose elevation=elevation filled=elevation_terraflow_depressionless memory=5000

for m in terraflow fill_dir hydrodem

do

r.mapcalc --o expression="${m}_effect=if((elevation_${m}_depressionless-elevation)>0,elevation_${m}_depressionless-elevation,null())"

done

r.univar map="terraflow_effect"

total null and non-null cells: 2025000

total null cells: 1901290

Of the non-null cells:

----------------------

n: 123710

minimum: 7.62939e-06

maximum: 12.5168

range: 12.5168

mean: 1.49711

mean of absolute values: 1.49711

standard deviation: 1.97871

variance: 3.91528

variation coefficient: 132.169 %

sum: 185206.976940155

r.univar map="fill_dir_effect"

total null and non-null cells: 2025000

total null cells: 1964852

Of the non-null cells:

----------------------

n: 60148

minimum: 7.62939e-06

maximum: 10.9003

range: 10.9003

mean: 0.499953

mean of absolute values: 0.499953

standard deviation: 0.939429

variance: 0.882526

variation coefficient: 187.903 %

sum: 30071.1971092224

r.univar map="hydrodem_effect"

total null and non-null cells: 2025000

total null cells: 1020396

Of the non-null cells:

----------------------

n: 1004604

minimum: 3.8147e-06

maximum: 4.74686

range: 4.74685

mean: 0.00587574

mean of absolute values: 0.00587574

standard deviation: 0.08715

variance: 0.00759513

variation coefficient: 1483.22 %

sum: 5902.79515457153

Cheers

Stefan

**Fra:** Markus Metz <[hidden email]>

**Sendt:** fredag 14. juni 2019 14.25

**Til:** Stefan Blumentrath

**Kopi:** [hidden email]

**Emne:** Re: [GRASS-dev] r.terraflow vs. r.hydrodem

On Fri, Jun 14, 2019 at 1:23 PM Stefan Blumentrath <

[hidden email]> wrote:

>

> Hi,

>

> While trying to make r.terraflow work with larger regions, I was wondering if it would be doable to add a flag to r.hydrodem that forces the module to perform only sink filling and no breaching / carving?

>

> Sink filling is the function I need from r.terraflow but if it would be an option to add this function to r.hydrodem, that would be fine as well of course...

what about r.fill.dir? It should work as is with larger regions.

Markus M

_______________________________________________

grass-dev mailing list

[hidden email]
https://lists.osgeo.org/mailman/listinfo/grass-dev