demgeotiff-tiffgrass
I have a DTM file, txt format, I would like to convert it into GeoTIFF, how can I do with the software grass?
ncols 1329
nrows 1152
xllcorner 1693884
yllcorner 5080341
cellsize 5
NODATA_value -9999
1120.142 1119.698 1119.085 1118.423 1117.761 1117.164 1116.76 1116.354 1115.948 1115.546 1115.151 1114.757 1114.265 1113.767 1113.534 1113.508 1113.482 1113.955 1114.433 1114.91 1115.124
A DTM raster can be represented by triangle meshes by finding a set of non-overlapping triangles that covers the entire mesh and approximates the elevation field. There are two different types of triangle meshes that can be used for this purpose:
In most applications, if you need to deal with elevation meshes, you'd go with a TIN since throwing out redundant or nearly redundant information allows for more efficient computations. However, creating TINs from rasters isn't straightforward, since there are many different triangulations that approximate a grid with the same error, but using different vertex sets.
Software for creating TINs
Raster to TIN function from the 3D Analyst toolbox.Grid to TIN (Surface Specific Points) function, followed by Export TIN to Stereo Lithography File (STL) function to export the TIN to a mesh format readable by Meshlab.Software for creating TRNs
Grid to TIN function.Roll your own solution: Implementing it isn't particularly hard. Here's a Python script that uses the GDAL library to read a raster DTM, and then writes out a binary PLY mesh.
Save the script as gdal_rastertotrn.py, then call it using python gdal_rastertotrn.py <inputraster> <outputply>.
Here's an example. Converting a raster DTM of Crater Lake called crater_lake.tif...
... by calling python gdal_rastertotrn.py crater_lake.tif crater_lake.ply, and opening the resulting crater_lake.ply in Meshlab:
Here's the (unpolished) script. Since it uses the GDAL library, it can convert all raster types supported by GDAL. It only writes PLY files.
#!/usr/bin/python
import sys
import numpy as np
from osgeo import gdal
def write_ply(filename, coordinates, triangles, binary=True):
template = "ply\n"
if binary:
template += "format binary_" + sys.byteorder + "_endian 1.0\n"
else:
template += "format ascii 1.0\n"
template += """element vertex {nvertices:n}
property float x
property float y
property float z
element face {nfaces:n}
property list int int vertex_index
end_header
"""
context = {
"nvertices": len(coordinates),
"nfaces": len(triangles)
}
if binary:
with open(filename,'wb') as outfile:
outfile.write(template.format(**context))
coordinates = np.array(coordinates, dtype="float32")
coordinates.tofile(outfile)
triangles = np.hstack((np.ones([len(triangles),1], dtype="int") * 3,
triangles))
triangles = np.array(triangles, dtype="int32")
triangles.tofile(outfile)
else:
with open(filename,'w') as outfile:
outfile.write(template.format(**context))
np.savetxt(outfile, coordinates, fmt="%.3f")
np.savetxt(outfile, triangles, fmt="3 %i %i %i")
def readraster(filename):
raster = gdal.Open(filename)
return raster
def createvertexarray(raster):
transform = raster.GetGeoTransform()
width = raster.RasterXSize
height = raster.RasterYSize
x = np.arange(0, width) * transform[1] + transform[0]
y = np.arange(0, height) * transform[5] + transform[3]
xx, yy = np.meshgrid(x, y)
zz = raster.ReadAsArray()
vertices = np.vstack((xx,yy,zz)).reshape([3, -1]).transpose()
return vertices
def createindexarray(raster):
width = raster.RasterXSize
height = raster.RasterYSize
ai = np.arange(0, width - 1)
aj = np.arange(0, height - 1)
aii, ajj = np.meshgrid(ai, aj)
a = aii + ajj * width
a = a.flatten()
tria = np.vstack((a, a + width, a + width + 1, a, a + width + 1, a + 1))
tria = np.transpose(tria).reshape([-1, 3])
return tria
def main(argv):
inputfile = argv[0]
outputfile = argv[1]
raster = readraster(inputfile)
vertices = createvertexarray(raster)
triangles = createindexarray(raster)
write_ply(outputfile, vertices, triangles, binary=True)
if __name__ == "__main__":
main(sys.argv[1:])
I image you want to capture vector data from your raster image. You can do it with GDAL however, I like PKTOOLS http://pktools.nongnu.org/html/pkpolygonize.html THEN convert the Shape file to SVG with Arc MAP or sho to AI or EPS then to SVG.
Best Answer
In GRASS GIS, use r.in.arc for the import or simply r.in.gdal (Menu: File -> Import raster data -> Common formats import). This should read the file right away.