Python, creating layers and rasterizing polygons in GDAL

Question

Trying to figure out how to rasterize in GDAL.

I have two problems (see example code below):

1) Even creating the raster layer with the gdal.GDT_Float32 type option, the resulting layer ('s bands) all end up being integer

2) In spite all efforts regarding noData setting, cells outside the polyons end up being set to zero.

# Create the destination data source
tempSource = rasterDriver.Create(tempRasterPath + tileName + "_Building.tif", tileHdl.RasterXSize, tileHdl.RasterYSize, gdal.GDT_Float32)
tempSource.SetGeoTransform(tileGeoTransformationParams)
tempTile = tempSource.GetRasterBand(1)
tempTile.SetNoDataValue(-999)
tempTile.Fill(-999)

# Rasterize
gdal.RasterizeLayer(tempSource, [1], buildingPolys.layer, options=["ATTRIBUTE=%s" % meanZAttributeName])
tempSource = None

Answer 1

Your issues are because you missed band parameter in created raster. So, I tried following code out:

from osgeo import gdal, ogr

tileHdl = "/home/zeito/pyqgis_data/aleatorio.tif"
tempRasterPath = "/home/zeito/pyqgis_data/"
tileName = "aleatorio"

vector_layer = "/home/zeito/pyqgis_data/buildingPolys.shp"

# open the raster layer and get its relevant properties
tileHdl = gdal.Open(raster_layer, gdal.GA_ReadOnly)

tileGeoTransformationParams = tileHdl.GetGeoTransform()
projection = tileHdl.GetProjection()

rasterDriver = gdal.GetDriverByName('GTiff')

buildingPolys_ds = ogr.Open(vector_layer)
buildingPolys = buildingPolys_ds.GetLayer()

# Create the destination data source
tempSource = rasterDriver.Create(tempRasterPath + tileName + "_Building.tif", 
                                 tileHdl.RasterXSize, 
                                 tileHdl.RasterYSize,
                                 1, #missed parameter (band)
                                 gdal.GDT_Float32)

tempSource.SetGeoTransform(tileGeoTransformationParams)
tempSource.SetProjection(projection)
tempTile = tempSource.GetRasterBand(1)
tempTile.Fill(-999)
tempTile.SetNoDataValue(-999)

gdal.RasterizeLayer(tempSource, [1], buildingPolys, options=["ATTRIBUTE=value"])
tempSource = None

with following layers:

and after running it, I got rasterized vector layer as expected.

As it can be observed at Metadata Layer Properties, nodata values were adequately set as -999 (it is also Float32 data type) .