[GRASS-user] Profile from a random path

[Michael Barton]

If you look at profile.tcl (in $GISBASE/etc/gm/) you can see how I used
r.profile to create the TclTk profiler. It draws continuous profiles of
multisegment transects.

BTW, the profiler is broken at the moment because r.univar has been renamed
to r.univar2 when it was enhanced.

If you rename r.univar2 back to r.univar it will be OK.

Michael


On 12/20/06 4:14 PM, "Dylan Beaudette" <dylan.beaudette at gmail.com> wrote:

> On Wednesday 20 December 2006 05:55, Hamish wrote:
>> Luca Casagrande wrote:
>>> I have got a path described by a vector line; i'd like to create the
>>> elevation profile for that line without using GUI.
>> 
>> maybe something with v.drape?
>> 
>>> 3) Use r.profile as described in the example 3 to create the profile
>>> for the ascii file.
>>> 
>>> I focused on the 3rd problem:
>>> 
>>> In the r.profile man page, in the example 3 section, it says this:
>>> [..]
>>> Example 3
>>> Extract a profile with coordinates provided from standard input or an
>>> external file: First create a points file with d.where
>>> d.where > saved.points
>>> Then pipe the points file into r.profile
>>> cat saved.points | r.profile input=elev.rast output=profile.pts
>>> [..]
>>> 
>>> The matter is that if i run the command line shown in the example, it
>>> doesn't work, cause it need -i flag or to set the profile= one with
>>> the coordinates of points.
>>> 
>>> Any idea?
>> 
>> The error message is wrong. That's been broken for ~6 years..
>> thanks for pointing it out. fixed in CVS + 6.2 branch.
>> 
>> 
>> Added this example to the help page:
>> 
>> #spearfish
>> r.profile elevation.dem res=1000 << EOF
>>   591243,4926344
>>   592509,4922156
>>   594100,4920793
>>   599910,4919365
>>   602929,4919235
>>   604844,4918391
>>   606468,4917190
>>   607766,4915664
>> EOF
>> 
>> 
>> this now works too:
>>  d.where | r.profile elevation.dem
>> 
>> 
>> Hamish
>> 
> 
> Luca:
> 
> did this solve your problem? I recall doing something like this a while back
> using v.drape.
> 
> If you like R here is the code I usually use for plotting distance along line
> (3d) vs elevation: (grass and R code):
> 
> # make new line
> v.digit -n map=t bgcmd="d.rast elev_meters"
> # convert to points
> v.to.points in=t out=tp type=line dmax=50 -i -v -t
> # set resolution
> g.region -pa res=4
> # make 3d
> v.drape in=tp out=tpz type=point rast=elev_4m method=cubic
> # export
> v.out.ascii tpz > tpz.txt
> 
> # start R
> R
> 
> # read in the data, note that there is no header, and the columns are pipe
> delimited
> x <- read.table('tpz.txt', header=F, sep="|",
> col.names=c('easting','northing','elev','f'))
> 
> # use attach for simple access to columns
> attach(x)
> 
> # compute the length minus 1 ; i.e. the number of points - 1
> # use for the lagged distance calculation
> s <- length(easting) - 1
> 
> # calculate the lagged distance along each component of the 3D vector
> dx <- easting[2:(s+1)] - easting[1:s]
> dy <- northing[2:(s+1)] - northing[1:s]
> dz <- elev[2:(s+1)] - elev[1:s]
> 
> # combine the vector components
> # 3D distance formula
> c <- sqrt( dx^2 + dy^2 + dz^2)
> 
> # create the cumulative distance along line:
> dist <- cumsum(c[1:s])
> 
> # plot the results
> plot(dist, elev[1:s], type='l', xlab='Distance from start (m)',
> ylab='Elevation (m)', main='Profile')
> 
> # cleanup
> detach(x)
> 
> 
> see attached figure for output
> 
> I can put this up on the R-wiki for later use. it might be fun to code this
> into something, so that there are fewer steps involved...
> 
> Cheers,
> 
> Dylan
> 

__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics and Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton