Write Latitude and Longitude to Geotiff file
Question:
I am basically trying to achieve the opposite of this question.
I have a set of latitude and longitude coordinates (with values) in the WGS84 coordinate system, that I would like to write to a geotiff (or just add to a gdal dataset) via the gdal python bindings.
For example, my starting data might be:
lat = np.array([45.345,56.267,23.425])
lon = np.array([134.689,128.774,111.956])
value = np.array([3.0,6.2,2.5])
How might one do this? Thanks!
Answers:
Although it is not in your question, it appears you need to project the lat/long data from the WGS84 datum to a UTM projection. This can be using the ogr2ogr command line from GDAL using the two options -a_srs 4326 -t_srs ???? (the target SRID). It can also be done internally with Python using the OGR module of GDAL. Here is an example of use.
There are two independent ways to get a raster from point data. The first is to interpolate the values in data, so that the values flood the region (or sometimes only the convex hull). There are many methods and tools to interpolate values in 2D. With GDAL, a comand-line tool gdal_grid is useful for this purpose, although I don’t think it is possible to use from Python. Probably the simplest would be to use scipy.interpolate. Once you have a 2D NumPy array, it is simple to create a raster file with GDAL/Python.
The second method of converting the points to a raster is to burn the point locations to pixels on a raster. Unlike the first method, only the locations where the points are have values, while the values are not interpolated anywhere else in the raster. Rasterising or burning vectors into a raster can be done from a GDAL command line tool gdal_rasterize. It can also be done internally with GDAL/Python, here is an example.
It is possible to use gdal_grid from Python. I am using it.
All you need to do is construct the command as if you were using it from the command line and put it inside a subprocess.call(com, shell=True). You need to import subprocess module first.
This is actually how I am using it:
pcall= "gdal_grid --config 'NUM_THREADS=ALL_CPUS GDAL_CACHEMAX=2000'
-overwrite -a invdist_power=2.0:smoothing=2.0:radius1=360.0:radius2=360.0
-ot UInt16 -of GTiff -outsize %d %d -l %s -zfield 'Z' %s %s "%(npx, npy,
lname,ptshapefile,interprasterfile)
subprocess.call(pcall, shell= True)
NUM_THREADS option is available from gdal 1.10+
I am basically trying to achieve the opposite of this question.
I have a set of latitude and longitude coordinates (with values) in the WGS84 coordinate system, that I would like to write to a geotiff (or just add to a gdal dataset) via the gdal python bindings.
For example, my starting data might be:
lat = np.array([45.345,56.267,23.425])
lon = np.array([134.689,128.774,111.956])
value = np.array([3.0,6.2,2.5])
How might one do this? Thanks!
Although it is not in your question, it appears you need to project the lat/long data from the WGS84 datum to a UTM projection. This can be using the ogr2ogr command line from GDAL using the two options -a_srs 4326 -t_srs ???? (the target SRID). It can also be done internally with Python using the OGR module of GDAL. Here is an example of use.
There are two independent ways to get a raster from point data. The first is to interpolate the values in data, so that the values flood the region (or sometimes only the convex hull). There are many methods and tools to interpolate values in 2D. With GDAL, a comand-line tool gdal_grid is useful for this purpose, although I don’t think it is possible to use from Python. Probably the simplest would be to use scipy.interpolate. Once you have a 2D NumPy array, it is simple to create a raster file with GDAL/Python.
The second method of converting the points to a raster is to burn the point locations to pixels on a raster. Unlike the first method, only the locations where the points are have values, while the values are not interpolated anywhere else in the raster. Rasterising or burning vectors into a raster can be done from a GDAL command line tool gdal_rasterize. It can also be done internally with GDAL/Python, here is an example.
It is possible to use gdal_grid from Python. I am using it.
All you need to do is construct the command as if you were using it from the command line and put it inside a subprocess.call(com, shell=True). You need to import subprocess module first.
This is actually how I am using it:
pcall= "gdal_grid --config 'NUM_THREADS=ALL_CPUS GDAL_CACHEMAX=2000'
-overwrite -a invdist_power=2.0:smoothing=2.0:radius1=360.0:radius2=360.0
-ot UInt16 -of GTiff -outsize %d %d -l %s -zfield 'Z' %s %s "%(npx, npy,
lname,ptshapefile,interprasterfile)
subprocess.call(pcall, shell= True)
NUM_THREADS option is available from gdal 1.10+