[GRASS-user] [GRASS-dev] how to sample a series at one location?

Fri Feb 22 13:13:00 PST 2013

Hi,
Am 22.02.2013 21:44 schrieb "Newcomb, Doug" <doug_newcomb at fws.gov>:
>
> t.create--> t.register--> t.vect.observer.strds   in GRASS7 ?   Looks
really nifty, could be useful with the Landsat Cube data sets
http://landsat.usgs.gov/documents/Oct27_29_2009_huang_LST_boston.ppt

Yes, thats the idea. I totally forgot, I made I short presentation and
tutorial at the geostat in 2012:
http://www.geostat-course.org/Topic_Gebbert

The presentation and the scripts are available there. The
t.vect.observe.strds example is in part three of the presentation. The cool
thing is that t.vect.observe.strds uses time stamped attribute tables to
store the values.

Best regards
Soeren
>
>
>
> Doug
>
>
> On Fri, Feb 22, 2013 at 2:53 PM, Michael Barton <Michael.Barton at asu.edu>
wrote:
>>
>> Thanks Doug,
>>
>> I knew I could do it with a script and v.what.rast.
>>
>> What I was hoping was that there is a shortcut already usable in GRASS
modules. Looks like the new temporal GIS tools may be able to do it.
>>
>> Michael
>> ______________________________
>> C. Michael Barton
>> Director, Center for Social Dynamics & Complexity
>> Professor of Anthropology, School of Human Evolution & Social Change
>> Arizona State University
>> Tempe, AZ  85287-2402
>> USA
>>
>> voice:  480-965-6262 (SHESC), 480-727-9746 (CSDC)
>> fax:          480-965-7671(SHESC), 480-727-0709 (CSDC)
>> www:  http://csdc.asu.edu, http://shesc.asu.edu
>> http://www.public.asu.edu/~cmbarton
>>
>> On Feb 22, 2013, at 12:31 PM, "Newcomb, Doug" <doug_newcomb at fws.gov>
>>  wrote:
>>
>>> Michael,
>>> You could use v.what.rast  in a python script , iterating the raster
layers with an sqlite database back end.  I think that would go up to 2000
columns for each point you have.
>>>
>>> Alternatively, you could use a bit of python with gdal.  I was trying
to do something similar in GRASS, to change the Z value of each point in a
text LiDAR file, from absolute above sea level to relative the elevation of
the ground.  For 25.5 billion text points and a Statewide 20 ft elevation
grid (6.5 ? billion cells) , it was a bit slow using r.what.  So I
converted the LiDAR data to (7)  3.3 billion point  LAS format files and
exported the GRASS layer to an Erdas imagine format file and wrote the
following ugly python script:
>>>
>>> #!/usr/bin/python
>>> import os,string,glob,re,gdal
>>> from liblas import file
>>> from liblas import header
>>> from liblas import point
>>> from gdalconst import *
>>> h=header.Header()
>>> #enter the LAS point file name
>>> infile=raw_input("Enter the input lidar data points file: ")
>>> #Hardcoded edras imagine file, you will have to use an array for the
different data layer names
>>> imgfile="/gisdata2/raster/allnc_20ft_el.img"
>>> #print "suggest /gisdata2/raster for output dir\n"
>>> inarr=infile.split('.')
>>> #This sets the LAS output file, substitute your output text file instead
>>> outfil=inarr[0]+"_norm.las"
>>> #outfil=raw_input("Enter output text file name: ")
>>> #This part reads the LAS file, if you
>>> l=file.File(infile,mode='r')
>>> #Outputs the LAS file
>>> lout=file.File(outfil,mode='w',header=h)
>>> # register all of the drivers, hopefully your gdal speaks GRASS
>>> gdal.AllRegister()
>>> #opening and closing the image layers might take some time if you are
reading thousands of images
>>> ds=gdal.Open(imgfile,GA_ReadOnly)
>>> if ds is None:
>>>     print 'Could not open image'
>>>     sys.exit(1)
>>> # get image size
>>> rows = ds.RasterYSize
>>> cols = ds.RasterXSize
>>> bands = ds.RasterCount
>>> # get georeference info, not sure how this would work for GRASS data
layers
>>> transform = ds.GetGeoTransform()
>>> xOrigin = transform[0]
>>> yOrigin = transformAsArray(xOffset, yOffset, 1, 1)
>>> pixelWidth = transform[1]
>>> pixelHeight = transform[5]
>>> for p in l:
>>>     x=float(p.x)
>>>     y=float(p.y)
>>>     z=float(p.z)
>>>     # compute pixel offset
>>>     xOffset = int((x - xOrigin) / pixelWidth)
>>>     yOffset = int((y - yOrigin) / pixelHeight)
>>>     band = ds.GetRasterBand(1) # 1-based index 0? 1?
>>>     data = band.Readr(value) :continue
>>>     value = data[0,0]
>>>     #print value,"11","\n"
>>>     if "nan" in st[3]
>>>     znorm = z-value
>>>     #print znorm,"\n"
>>>     pt=point.Point()
>>>     pt.x=p.x
>>>     pt.y=p.y
>>>     pt.z=znorm
>>>     lout.write(pt)
>>>
>>> l.close()
>>> lout.close()
>>> #25561312019 points in allreturns
>>>
>>> This managed to process everything over a weekend( in 7 parallel
threads), which was fast enough for me at the time.  Approaching your
problem , if your data layers are all n GRASS and your version of gdal can
read GRASS data layers,  I would grab the list of GRASS layers via glob and
iterate the layers , writing the name of the raster layer and the value of
the raster layer at the point coordinates out to a text file as you state
below.
>>>
>>> Hope this helps,
>>> Doug
>>>
>>>
>>> On Fri, Feb 22, 2013 at 1:23 PM, Michael Barton <Michael.Barton at asu.edu>
wrote:
>>>>
>>>> But I want to do it with a time series of hundreds or thousands of
maps.
>>>>
>>>> Michael
>>>> ______________________________
>>>> C. Michael Barton
>>>> Director, Center for Social Dynamics & Complexity
>>>> Professor of Anthropology, School of Human Evolution & Social Change
>>>> Arizona State University
>>>> Tempe, AZ  85287-2402
>>>> USA
>>>>
>>>> voice:  480-965-6262 (SHESC), 480-727-9746 (CSDC)
>>>> fax:          480-965-7671(SHESC), 480-727-0709 (CSDC)
>>>> www:    http://csdc.asu.edu, http://shesc.asu.edu
>>>>                 http://www.public.asu.edu/~cmbarton
>>>>
>>>> On Feb 22, 2013, at 10:53 AM, Markus Neteler <neteler at osgeo.org>
>>>>  wrote:
>>>>
>>>> > On Fri, Feb 22, 2013 at 6:41 PM, Michael Barton <
Michael.Barton at asu.edu> wrote:
>>>> >> Is there tool somewhere, including in the new temporal GIS modules,
to
>>>> >> sample the value of a raster series at one cell location? I'd like
to get
>>>> >> text something like this for a cell that I specify with xy
coordinates or a
>>>> >> cat:
>>>> >>
>>>> >> map1, value 1
>>>> >> map2, value 2
>>>> >> map3, value 3
>>>> >> map4, value 4
>>>> >> map5, value 5
>>>> >> …
>>>> >>
>>>> >
>>>> > I do such queries with r.what which accepts multiple input:
>>>> >
>>>> > http://grass.osgeo.org/grass64/manuals/r.what.html
>>>> >
>>>> > Markus
>>>>
>>>> _______________________________________________
>>>> grass-dev mailing list
>>>> grass-dev at lists.osgeo.org
>>>> http://lists.osgeo.org/mailman/listinfo/grass-dev
>>>
>>>
>>>
>>>
>>> --
>>> Doug Newcomb
>>> USFWS
>>> Raleigh, NC
>>> 919-856-4520 ext. 14 doug_newcomb at fws.gov
>>>
---------------------------------------------------------------------------------------------------------
>>> The opinions I express are my own and are not representative of the
official policy of the U.S.Fish and Wildlife Service or Dept. of the
Interior.   Life is too short for undocumented, proprietary data formats.
>>
>>
>
>
>
> --
> Doug Newcomb
> USFWS
> Raleigh, NC
> 919-856-4520 ext. 14 doug_newcomb at fws.gov
>
---------------------------------------------------------------------------------------------------------
> The opinions I express are my own and are not representative of the
official policy of the U.S.Fish and Wildlife Service or Dept. of the
Interior.   Life is too short for undocumented, proprietary data formats.
>
> _______________________________________________
> grass-dev mailing list
> grass-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-dev
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