Gdal_value = struct.unpack('f', band.ReadRaster(x, y, 1, 1, buf_type=band. # Read band 1 at the middle of the raster ( x = 500, y = 1000) We will open the file in Python, and have a look at finding a particular location.
PYTHON GDAL OPEN HOW TO
The upper left corner of the upper left pixel isĪt position (padfTransform,padfTransform). The first part of the unit will provide a short demonstration of how to open a remote sensing raster dataset using GDAL and read the geo-information contained within the file. GDAL provides a very handy way of dealing with raster data in many. In a north up image, padfTransform is the pixel width, and padfTransform Yp = padfTransform + P*padfTransform + L*padfTransform
PYTHON GDAL OPEN DRIVERS
Once the drivers are registered, the application should call the free standing GDALOpen() function to open a dataset, passing the name of the dataset and the access desired (GAReadOnly or GAUpdate). The order it tries to open them is the same order as listed in ogrinfo -formats. It will loop over all the drivers until it finds a driver with that it can open your file. If you don't specify it, OGR will try to open your file with all the drivers. Xp = padfTransform + P*padfTransform + L*padfTransform Python automatically calls GDALAllRegister() when the gdal module is imported. If you specify a driver, OGR will only try to open your file with the specified driver. # Read the cell with this raster coordinatesįetches the coefficients for transforming between pixel/line (P,L) raster space,Īnd projection coordinates (Xp,Yp) space. # You need this to convert raw values readings from GDAL This tutorial explains how to read raster data as an array and save arrays as a GeoTiff file using the GDAL library in Python. Another great source of examples is OGR’s autotest directory. We heavily relied on Chris Garrard’s excellent Geoprocessing with Python using Open Source GIS and the official GDAL/OGR Python documentation. # First layer in QGIS project is a DTM 2 bands raster For a detailed description of the whole Python GDAL/OGR API, see the useful API docs. The example raster layer is a DTM with 1000 cells width and 2000 cells height, we want to read the value at the cell with coordinates x = 500 and y = 1000. Here is a short example about how to do it with the two different approaches, we assume that you are working inside the QGIS python console and the project has a raster file loaded, but with just a few modifications, the example can also be run from a standard python console. Google+QGIS and GDAL both have Python bindings, you can use both libraries to read a value from a raster cell, since QGIS uses GDAL libraries under the hood, we can expect to read the exact same value with both systems.