[GRASS-user] Newbie Q - how do I use addons?

Fri Jun 13 02:24:31 PDT 2014

Vaclav, thank you for your comprehensive answer.

You answered to my original question with ‘in the module tree under search modules’, thank you! A thought: is this explained anywhere in the GRASS documentation for addons? If not, how do I request that this information is included? Its rather fundamental and it would save this mailing list being hassled but such trivialities.

Probably I should have put the commands that I had tried previously so that it was clear that I’m not a total numpty. I understood how to use the manual, that I have to define the DEM (and what a DEM is), and that there are 4 other required parameter which have defaults (and what these parameters are, and that I need to experiment to find the most useful for my application but thank you for explaining). In fact I have even studied to quite some detail the published work pertaining to this addon.

What I couldn’t fathom was how to tell GRASS where to put the output, this is clearer now I understand that <name> specifically pertains to names of maps (although I still am not sure how I tell which are input maps and which are output maps). From your response I have used the additional parameter ‘forms=<name>’ and this worked. I even worked out that I need to add the new map layer to the layer tree to display it ;-) .

It took several tests to learn that ‘forms=name: Most common geomorphic forms’ does not mean that I have to give the name of one of the 10 popular land forms but rather than the output is called <name> and contains the 10 most popular land forms. I had a similar misunderstanding of the definitions for other parameters.

I hope I am now correct in understanding that this function also has a further required parameter which needs to be one of <forms, ternary, positive, negative, intensity, exposition, range, variance, elongation, azimuth, extend, width> and that the values for these are the name of the output raster. I believe this could be much clearer in the documentation.

Thank you also for your hint for getting the GUI using the command prompt – very useful!

Izzy

From: Vaclav Petras [mailto:wenzeslaus at gmail.com]
Sent: 12 June 2014 15:35
To: Isabel Sargent
Cc: Micha Silver; grass-user at lists.osgeo.org
Subject: Re: [GRASS-user] Newbie Q - how do I use addons?

On Thu, Jun 12, 2014 at 9:16 AM, Isabel Sargent <Isabel.Sargent at ordnancesurvey.co.uk<mailto:Isabel.Sargent at ordnancesurvey.co.uk>> wrote:
Thank you for such a prompt response. I had read through the manual pages online (though I couldn’t get the man command to work, perhaps because I’m using windows?). Those last 4 required fields have defaults, so in my question I was assuming that I didn’t need to explicitly set them. Even if I do set them I get the error requiring an output. I don’t think this in itself is a r.geomorphon issue, there is probably a standard way of defining an output (neither | or > work). I’m sure there must be examples on how to do this somewhere, I just can’t find them.

r.geomorphon should work on MS Windows.
In manual page (http://grass.osgeo.org/grass70/manuals/addons/r.geomorphon.html) I can see 5 required parameters (options):
dem=name [required]
Input dem
search=integer [required]
Outer search radius
Default: 3
skip=integer [required]
Inner search radius
Default: 0
flat=float [required]
Flatenss treshold (degrees)
Default: 1
dist=float [required]
Flatenss distance, zero for none
Default: 0
Four have default but dem does not. This is the elevation raster map, your input. You should also specify output, this is option forms, this will be the name of newly created raster map containing identified forms. This is what the message 'ERROR: At least one output is required' was telling you, it wanted you to specify one of the outputs. (The interface does not follow GRASS naming conventions, that's one of the reasons why it is an addon. This might be improved in the future.)

Note that to get really nice output from r.geomorphon you have to play with the parameters such as search, skip, flat and dist a little bit.
| and > are linux/unix command line features which allows you to direct standard input and output of the programs. This is applicable to some of the GRASS modules but most of them outputs "grass maps" (raster or vector) and there are specified by setting certain options to a name of the raster map. This is what manual page will tell you.

Am I right in expecting to be able to find installed addons use the GUI? If so, where will I find them? If not, how do I define an output at the command prompt?

Yes and no. They are not in menu (to keep it short) but installed addons are in the module tree in Search modules tab (3rd tab by default in layer manager). You have to restart GRASS (or just GUI if you use command line and know g.gui command) to get the updated list.
You can always type r.geomorphon to Command console in GUI and you will get the dialog to fill parameters (including inputs and outputs) for r.geomorphon. This works for every command, form addons or standard one.

Let us know if you have any further problems.
Vaclav

Izzy

From: Micha Silver [mailto:micha at arava.co.il<mailto:micha at arava.co.il>]
Sent: 12 June 2014 13:56
To: Isabel Sargent; grass-user at lists.osgeo.org<mailto:grass-user at lists.osgeo.org>
Subject: Re: [GRASS-user] Newbie Q - how do I use addons?

On 12/06/2014 15:20, Isabel Sargent wrote:

Sorry, the answer to my question must be somewhere but I have been searching for 90 minutes and have found nothing, please humour me.

I GRASS 7.0.0BETA2 installed on Windows 7. All looks fine. I have installed the r.geomorphon addon without any errors and have checked in the installed extensions manager that it appears to be installed. My problem is, what now?

I can't find r.geomorphon in any of the lists in the gui. If I use command line, I cannot work out how to tell GRASS where to put the output (do I have to pipe somewhere? How should I do this?). Command line is not happy with simply 'r.geomorphon dem=<name>' => 'ERROR: At least one output is required'
I'm not familiar with the addon, but typing "r.geomorphon help " in the command line gives a brief help message. And "man r.geomorphon" opens the whole manual page.
The required parameters are "dem" (input) and "search", "skip", "flat" and "dist" (numeric parameters).

Please just point me to some examples and I'll stop being so annoying!

Izzy

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