Calculate NDVI using Python

python arcpy
user2278713 picture user2278713 · May 7, 2013 · Viewed 7.8k times · Source

I know that the NDVI equation is 

NDVI = (NIR — VIS)/(NIR + VIS)

I'm trying to calculate it using python. I've got this so far:

inRaster = ('Landsat.tif')
out_NDVI_file = ('NDVI.tif')

red = arcpy.Describe(inRaster+'/Band_3')
NIR = arcpy.Describe(inRaster+'/Band_4')

num = arcpy.sa.Float(NIR-red)
denom = arcpy.sa.Foat(NIR+red)
NDVI = arcpy.sa.Divide(num, denom)

NDVI.Save(out_NDVI_file)

but i get this error message,

Traceback (most recent call last):
  File "F:\abc\def.py", line 32, in <module>
    num = arcpy.sa.Float(NIR-red)
TypeError: unsupported operand type(s) for -: 'geoprocessing describe data object' and 'geoprocessing describe data object'

Any ideas on what I am doing wrong?

Answer

Jon Snow picture Jon Snow · Aug 27, 2013

If you replace 

red = arcpy.Describe(inRaster+'/Band_3')
NIR = arcpy.Describe(inRaster+'/Band_4')

with

red = arcpy.sa.Raster(inRaster+'/Band_3')
NIR = arcpy.sa.Raster(inRaster+'/Band_4')

your script should work as expected.

Related questions

python dict to numpy structured array

I have a dictionary that I need to convert to a NumPy structured array. I'm using the arcpy function NumPyArraytoTable, so a NumPy structured array is the only data format that will work. Based on this thread: Writing to numpy …

Read More
Unzip all zipped files in a folder to that same folder using Python 2.7.5

I would like to write a simple script to iterate through all the files in a folder and unzip those that are zipped (.zip) to that same folder. For this project, I have a folder with nearly 100 zipped .las files …

Read More
Python extract data from xml and save it to excel

I would like to extract some data from an XML file and save it in a table format, such as XLS or DBF. Here is XML file i have: <?xml version="1.0" encoding="utf-8"?> <SOAP-ENV:Envelope xmlns:SOAP-ENV="…

Read More