I have setup GRASS 5.0 and all seems to be working perectly. I have determined how to create a new project and import vector (dxf) and raster (8bit tiled TIFFs) layers. Now I am trying to determine how I might be able to draw a polygon and import one dxf (known) then use that polygon as a mask or cropping line then in turn right out the area still visible of the TIFF. I am also curious about rotation and transformation (2d) of the rasters.
Can anyone direct me to a good tutorial on this. I have been searching for awhile but can not seem to find anything specific. I have tinkered with creating masks but I am not sure if I am doing it correctly nor how I would use one once I have it created.
Also I have not looked into this much as of yet but does anyone have a suggestion on a good 3D tutorial? ie: Drapping Orthorectified imagery over a point surface (dem/dtm)?
Thanks,
Jason Nielsen
PS. I am a total newbie to GRASS and GIS is not my field of expertise.
Now I am trying to determine how I might be able to draw a polygon and
import one dxf (known) then use that polygon as a mask or cropping
line then in turn right out the area still visible of the TIFF.
read the man page for r.in.poly. I think making a poly file and importing it, then using r.mask and r.mapcalc croppedTIFF=importedTIFF would do the trick.
I have setup GRASS 5.0 and all seems to be working perectly. I have
determined how to create a new project and import vector (dxf) and
raster (8bit tiled TIFFs) layers. Now I am trying to determine how I
might be able to draw a polygon and import one dxf (known) then use that
polygon as a mask or cropping line then in turn right out the area still
visible of the TIFF.
First, either:
a) use r.in.poly to import a polygon definition directly as a raster
map, or
b) use one of the v.in.* programs to import a file as a vector map
then convert it to a raster map with v.to.rast.
Then, to use the raster map as a mask, copy it (or rename it) to
"MASK", e.g. "g.copy rast=mapname,MASK".
Finally, to create a masked version of an existing raster map, use
r.resample.
I am also curious about rotation and transformation
(2d) of the rasters.
r.proj will transform rasters between coordinate systems, while
i.rectify performs image rectification.
This is not quite a GRASS question, but perhaps some of the GRASSLIST participants have suggestions.
I would like to do some do-it-yourself mapping of sites, lines, and areas in a region for which I already have good vector and raster maps. I thought that I would use a handheld GPS (Global Positioning System) device (1) to take location readings at the sites (waypoints in GPS terminology), and then (2) upload the sites data to the computer for import to GRASS with s.in.ascii. (I suppose that I can then use s.to.vect and v.digit to create areas, lines, etc. or I can directly edit dig_ascii, dig_att, and dig_cats files according to ascii_formats.html.)
My question is about GRASS users' experience with low-budget GPS hardware (e.g., Garmin eTrex Venture) and about interfaces between GPS devices and the PC (linux or Windows). Please let me know if you have any suggestions or advice
Michael Ash writes:
> My question is about GRASS users' experience with low-budget GPS
> hardware (e.g., Garmin eTrex Venture) and about interfaces between
> GPS devices and the PC (linux or Windows). Please let me know if
> you have any suggestions or advice
I'm running pygps over gpsd to have access to my Linux iPAQ's Navman
sleeve. pygps keeps a log of every location reported by the gps
receiver (every two seconds). That log is stored in an ASCII file,
one location per line. A very simple awk script could separate it out
into whatever file format grass needed.
--
-russ nelson http://russnelson.com |
Crynwr sells support for free software | PGPok | it's better to be free
521 Pleasant Valley Rd. | +1 315 268 1925 voice | than to be correct.
Potsdam, NY 13676-3213 | +1 315 268 9201 FAX |