Hi,
I am new to pygrass, I got the landsat processing script from osgeo pygrass wiki page. I am stuck here at looping through landsat directories that I have already created through unzipping lansat .gz archives. Kindly assist, code is a shown below, the error being raised is for L7Dir in L7Dirs:
TypeError: ‘NoneType’ object is not iterable
#!/usr/bin/env python
PURPOSE
This script processes LANDSAT 7 ETM+ images
1 - unzip *.gz files
2 - import files in GRASS GIS Location of your choice (r.in.gdal)
3 - DN to Top of Atmosphere reflectance (i.landsat.toar)
4 - TOA reflectance to Surface reflectance (i.atcorr)
5 - NDVI (i.vi), Albedo (i.albedo), Emissivity (i.emissivit
USER HAS TO SET THOSE
QUIET REPORTS
QIET = True
OVERWRITE EXISTING FILES
OVR = False
Define Landsat 7 sensor for i.landsat.toar
LSENSOR = “tm7”
Setup the path to the Landsat 7 Directories
rsdatapath = “~/rawData/L7Dir”
set L7 Metadata wildcards
wldc_mtl = “*_MTL.txt”
Visibility distance [Km]
vis = 18
DEM input to atmospheric correction
inDEM = rsdatapath + “/dem_30m/Kenya_SRTM30meters.tif”
import glob
import os
import subprocess
import sys
path to the GRASS GIS launch script
MS Windows
grass7bin_win = r’C:\OSGeo4W\bin\grass72svn.bat’
uncomment when using standalone WinGRASS installer
grass7bin_win = r’C:\Program Files (x86)\GRASS GIS 7.2.0\grass72.bat’
Linux
grass7bin_lin = ‘grass72’
Mac OS X
grass7bin_mac = ‘/Applications/GRASS/GRASS-7.2.app/’
DATA
define GRASS DATABASE
add your path to grassdata (GRASS GIS database) directory
gisdb = os.path.join(os.path.expanduser(“~”), “rawData”)
the following path is the default path on MS Windows
gisdb = os.path.join(os.path.expanduser(“~”), “Documents/grassdata”)
specify (existing) location and mapset
location = “L7_Kenya”
mapset = “hempire”
SOFTWARE
if sys.platform.startswith(‘linux’):
we assume that the GRASS GIS start script is available and in the PATH
query GRASS 7 itself for its GISBASE
grass7bin = grass7bin_lin
else:
raise OSError(‘Platform not configured.’)
query GRASS 7 itself for its GISBASE
startcmd = [grass7bin, ‘–config’, ‘path’]
p = subprocess.Popen(startcmd, shell=False,
stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = p.communicate()
if p.returncode != 0:
print >> sys.stderr, “ERROR: Cannot find GRASS GIS 7 start script (%s)” % startcmd
sys.exit(-1)
gisbase = out.strip(‘\n\r’)
Set GISBASE environment variable
os.environ[‘GISBASE’] = gisbase
the following not needed with trunk
os.environ[‘PATH’] += os.pathsep + os.path.join(gisbase, ‘extrabin’)
add path to GRASS addons
home = os.path.expanduser(“~”)
os.environ[‘PATH’] += os.pathsep + os.path.join(home, ‘.grass7’, ‘addons’, ‘scripts’)
define GRASS-Python environment
gpydir = os.path.join(gisbase, “etc”, “python”)
sys.path.append(gpydir)
DATA
Set GISDBASE environment variable
os.environ[‘GISDBASE’] = gisdb
import GRASS Python bindings (see also pygrass)
import grass.script.setup as gsetup
gsetup.init(gisbase, gisdb, location, mapset)
from grass.pygrass.modules.shortcuts import raster as r
Needed for floor()
env = os.environ.copy()
env[‘GRASS_MESSAGE_FORMAT’] = ‘gui’
Function to get a list of L7 Directories in the rsdatapath
def fn(path):
for top, dirs, files in os.walk(path):
return [os.path.join(top, dir) for dir in dirs]
START PROCESS
PART 0: PRE-PROCESSING STUFF
import DEM for atmospheric correction
r.in.gdal(input=inDEM,output=“dem”,overwrite=OVR)
r.mapcalc(expression=“dem=25”,overwrite=OVR)
create a visibility map
r.mapcalc(expression=“vis=18”, overwrite=OVR)
Find the central location of the Landsat file from metadata
metadata =
fileList =
L7Dirs = fn(rsdatapath)
for L7Dir in L7Dirs:
Ungzip all of your Landsat7 images in all your directories
print “Ungzip Landsat files in\t”,L7Dir
p=os.system(“gzip -d -q “+L7Dir+”/*.gz”)
Using pthreads on multi-core machines
p=os.system(“pigz -d “+L7Dir+”/*.gz”)
Wait ten seconds for gzip to create the tif images
time.sleep(10)
print “Import in GRASS GIS”
···
Kind Regards,
Joseph Kariuki
Geospatial Engineer | GIS / Web Developer