[R-sig-Geo] Slope and Aspect calculations in R

[Thomas Adams]

Tom,

Thanks! I have seen your posts and results of some of your work with 
SAGA and I am very interested. But, I have been to lazy to this point to 
try compiling SAGA for either MacOS X or Linux (is a Linux distribution 
available?).

Regards,
Tom

Tomislav Hengl wrote:
> Dear Josh, Thomas,
>
> I typically use R+SAGA (R on top!) for such type of analysis (and I do have access to all operating
> system/software). There must be some good reasons that I am using SAGA (speed, stability, rich
> geomorphometry module etc.)! So do not give up so easy on SAGA.
>
> I especially like that SAGA is fairly efficient in processing big grids, and the commands are rather
> compact. For example to reproject grids from one to another proj4string, you only need to set e.g.:
>
>   
>> rsaga.geoprocessor(lib="pj_proj4", 2, param=list(SOURCE_PROJ=paste('"', proj4string(dem25m), '"',
>>     
> sep=""), TARGET_PROJ="\"+proj=longlat +datum=WGS84\"", SOURCE="TWI.sgrd", TARGET="TWI_ll.sgrd",
> TARGET_TYPE=0, INTERPOLATION=0))
>
> *see http://www.geomorphometry.org/R.asp 
>
> I remember that somebody did manage to set-up SAGA also under Mac OS
> (http://www.saga-gis.uni-goettingen.de/html/index.php?module=pnForum&func=viewtopic&topic=458), but
> I also remember that most of students on our GEOSTAT course used Windows under Mac OS to run SAGA. I
> am sure that it should be possible to compile SAGA under Mac OS, but somebody needs to put some
> effort to bridge this gap (check also with Olaf Conrad).
>
> Here is more discussion about the same topic from few months ago:
> https://stat.ethz.ch/pipermail/r-sig-geo/2009-April/005418.html 
>
> cheers,
>
> Tom Hengl
>
>
>   
>> -----Original Message-----
>> From: r-sig-geo-bounces at stat.math.ethz.ch [mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf
>> Of Thomas Adams
>> Sent: Friday, July 10, 2009 3:12 PM
>> To: Josh London
>> Cc: r-sig-geo at stat.math.ethz.ch
>> Subject: Re: [R-sig-Geo] Slope and Aspect calculations in R
>>
>> Josh,
>>
>> I use R & GRASS together on both MacOS X and Linux without problems.
>> It's very direct to write a shell script that calls both R & GRASS
>> within a single script. Writing a R script that calls GRASS may be more
>> tedious to do what you want. Writing a shell script that calls both may
>> be the wat to go.
>>
>> Tom
>>
>> Josh London wrote:
>>     
>>> Thanks for the suggestions so far regarding the use of GRASS or SAGA.
>>>
>>> We have considered those options but SAGA doesn't appear available for
>>> MacOS. My understanding is that spgrass6 is more for accessing R
>>> code/functions from within GRASS vs accessing GRASS functions from
>>> within R. We have all our other analysis coded up in R, and just need
>>> these functions to do one part of a bigger process. Maybe I'm
>>> misunderstanding how to use R and GRASS together. I'll do some further
>>> research.
>>>
>>> Thanks again
>>> Josh
>>>
>>> Josh London wrote:
>>>       
>>>> Hello
>>>>
>>>> We are looking to mimic, in R, the slope (max magnitude difference
>>>> between a cell and its neighbors) and aspect (direction of maximum
>>>> magnitude difference) functions found in ESRI's Spatial Analyst
>>>> package. We were just about to code up the slope function but thought
>>>> I would make sure we weren't re-inventing any wheels already out there.
>>>>
>>>> Thanks
>>>> Josh
>>>>
>>>>         
>> --
>> Thomas E Adams
>> National Weather Service
>> Ohio River Forecast Center
>> 1901 South State Route 134
>> Wilmington, OH 45177
>>
>> EMAIL:	thomas.adams at noaa.gov
>>
>> VOICE:	937-383-0528
>> FAX:	937-383-0033
>>
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>>     
>
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-- 
Thomas E Adams
National Weather Service
Ohio River Forecast Center
1901 South State Route 134
Wilmington, OH 45177

EMAIL:	thomas.adams at noaa.gov

VOICE:	937-383-0528
FAX:	937-383-0033