Thanks for your help!
At least i’ve got the solution. I was confused about the cost because a colleague of mine used it in another algorithm.
Now th max. Cost work as well.
Gesendet: Dienstag, 25. Oktober 2016 um 03:07 Uhr
Von: “Anna Petrášová” kratochanna@gmail.com
An: “Phil Burgdorf” P_Burgdorf@web.de, “GRASS user list” grass-user@lists.osgeo.org
Betreff: Re: Re: Re: Re: [GRASS-user] r. walk and sites which can be reached in a certain time
Please, keep the conversation on the mailing list.
On Mon, Oct 24, 2016 at 12:31 PM, Phil Burgdorf P_Burgdorf@web.de wrote:
I use Grass together with QGIS.
So i donÄt know how to give you the command. I’ll send you the r. info for
may input data and wrote down what I#ve done, I hope that’ll give yo the
information you need.
First i calculated the speed km/h with this formula (6e ^-3,5Islope + 0,05)
(layername:Test_Neo_Geschw)
r. info for that:
Map: tmp1477325189748 Date: Mon Oct 24 18:06:30 2016 |
| Mapset: PERMANENT Login of Creator: Phil |
| Location: temp_location |
| DataBase: C:\Users\Phil\AppData\Local\Temp\processing99ff3938206843eb8f58e
|
| Title: ( tmp1477325189748 ) |
| Timestamp: none |
|
| Type of Map: raster Number of Categories: 0 |
| Data Type: FCELL |
| Rows: 7832 |
| Columns: 9000 |
| Total Cells: 70488000 |
| Projection: unnamed |
| N: 5598800 S: 5403000 Res: 25 |
| E: 4585500 W: 4360500 Res: 25 |
| Range of data: min = 0.05126764 max = 0.1423827 |
After that the cost with c = 60 /v (layer name: Test_Neo_Kosten)
r. info for that:
Map: tmp14773254289710 Date: Mon Oct 24 18:10:29 2016 |
| Mapset: PERMANENT Login of Creator: Phil |
| Location: temp_location |
| DataBase: C:\Users\Phil\AppData\Local\Temp\processing99ff3938206843eb8f58e
|
| Title: ( tmp14773254289710 ) |
| Timestamp: none |
|
| Type of Map: raster Number of Categories: 0 |
| Data Type: FCELL |
| Rows: 7832 |
| Columns: 9000 |
| Total Cells: 70488000 |
| Projection: unnamed |
| N: 5598800 S: 5403000 Res: 25 |
| E: 4585500 W: 4360500 Res: 25 |
| Range of data: min = 421.3996 max = 1170.329 |
In r. walk I used the slope of my test region (layername: Test_Neo_Slope) as
elevation raster and the layer " Test_Neo_Kosten" as input raster for the
why do you use slope as elevation raster? It should be elevation,
slope is computed internally. Also, I don’t really understand how you
define the cost. You should define friction as additional time to
cross a cell depending on landcover for example. I suggest looking at
r.walk manual, also look at:
http://www.bioone.org/doi/full/10.1659/MRD-JOURNAL-D-13-00041.1
where r.walk is used.
friction cost. my starting ponit is a simple shape-point in this region. The
first result is fine. The algorithm creates a map in my test region. I
have’nt changed all the other values. As i told you the algorithm fails when
I change the Max. cost.
r.info for r.walk:
| Map: tmp14773265793514 Date: Mon Oct 24 18:29:43 2016 |
| Mapset: PERMANENT Login of Creator: Phil |
| Location: temp_location |
| DataBase: C:\Users\Phil\AppData\Local\Temp\processing99ff3938206843eb8f58e
|
| Title: ( tmp14773265793514 ) |
| Timestamp: none |
|
| Type of Map: raster Number of Categories: 0 |
| Data Type: DCELL |
| Rows: 7832 |
| Columns: 9000 |
| Total Cells: 70488000 |
| Projection: unnamed |
| N: 5598800 S: 5403000 Res: 25 |
| E: 4585500 W: 4360500 Res: 25 |
| Range of data: min = 0 max = 775143.701578344 |
I hope these informations are more helpfull.
Gesendet: Montag, 24. Oktober 2016 um 17:46 Uhr
Von: “Anna Petrášová” kratochanna@gmail.com
An: “Phil Burgdorf” P_Burgdorf@web.de
Betreff: Re: Re: Re: [GRASS-user] r. walk and sites which can be reached in
a certain time
On Mon, Oct 24, 2016 at 11:41 AM, Phil Burgdorf P_Burgdorf@web.de wrote:
Thank you for the formula. I replaced “time to walk” by my layer named
“acumulated_cost”.
So it’s now: “accumulated_cost_limited = if(acumulated_cost < 3600,
acumulated_cost,null())” Is that right?
After running the caclculator I didn’t get a new raster map althogh it
says
“algorithm finished”
You have to provide more information. What does r.info acumulated_cost
show? What’s the r.walk command you used and what are the input data?
Did you set the computational region to match your input data (see
g.region)?
Gesendet: Montag, 24. Oktober 2016 um 16:34 Uhr
Von: “Anna Petrášová” kratochanna@gmail.com
An: “Phil Burgdorf” P_Burgdorf@web.de, “GRASS user list”
grass-user@lists.osgeo.org
Betreff: Re: Re: [GRASS-user] r. walk and sites which can be reached in a
certain time
On Mon, Oct 24, 2016 at 10:22 AM, Phil Burgdorf P_Burgdorf@web.de wrote:
Hi Anna,
thanks for your answer. I’ve tried to use 3600 as max. Cost but the
algorithm failed.
That’s weird.
The values for min and max for the cummulative cost are “nan”. But I
don’t
know why!
How can I do this in r. mapcalc. I haven’t used it before
r.mapcalc “time_to_walk_limited = if(time_to_walk < 3600, time_to_walk,
null())”
Please keep the discussion on the mailing list.
Phil
Gesendet: Montag, 24. Oktober 2016 um 16:02 Uhr
Von: “Anna Petrášová” kratochanna@gmail.com
An: “Phil Burgdorf” P_Burgdorf@web.de
Cc: “GRASS user list” grass-user@lists.osgeo.org
Betreff: Re: [GRASS-user] r. walk and sites which can be reached in a
certain time
On Mon, Oct 24, 2016 at 7:52 AM, Phil Burgdorf P_Burgdorf@web.de wrote:
Hello there,
my name is Phil and I’m a PhD Student in Archaeology and I’m analiesing
a
small area in bavaria. I’m trying to locate archaeological sites round
different strating points. Therefor I created a cost map using r. walk.
The
result is fine but how can I adapted my values. Actualy I’m interrested
in
sites which can be reached in, let’s say, one hour. I’ve tried to change
the values for max costs but I didn’t get any results. Do i have to use
a
nother algorithm? here must be an easy way to define the max cost for
that
analysis.
I couldn’'t find any help in the mailing list’s archive and I#m totally
lost. Can you help me?
max_cost will do the trick, don’t forget that the time is in seconds.
You can also use raster algebra (r.mapcalc) to extract the area within
certain time.
Anna
Cheers
Phil
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