Extracting rasters from NetCDF files based on time dimension

09-11-2016 10:18 PM
Occasional Contributor III

I have single netCDF file which contain monthly data for different year. (Format of date e.g 2001-1-1, 2001-2-1, 2001-3-1…….2002-12-1...............2015-0-1......2015-12-1). 

Here-with i have attached a snapshot of data format from Arc GIS multidimension tool 

I trying to extract each month raster for selected year (e.g only 2002). Save it as 01-2002, 02-2002, 03-2002…..12-2002.

I appreciate any help you can provide on the crucial bottom code.

Here is what I have so far:


# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

outLoc = r"D:\MODIS_NPP_02_15"
inNetCDF = r"D:\MODIS_NPP_02_15\NPP_2001_15.nc"

variable = "npp"
x_dimension = "lon"
y_dimension = "lat"
band_dimension = ""
dimension = "time"
valueSelectionMethod = "BY_VALUE"

nc_FP = arcpy.NetCDFFileProperties(inNetCDF)
nc_Dim = nc_FP.getDimensions()

for dimension in nc_Dim:
        if dimension == "time":
            top = nc_FP.getDimensionSize(dimension)
            for i in range(0, top):

                dimension_values = nc_FP.getDimensionValue(dimension, i)
                nowFile = str(dimension_values)
                nowFile = nowFile.translate(None, '/')
                # I needed only the years 2002
                if int(nowFile[-12]) > 6:

                    dv1 = ["time", dimension_values]
                    dimension_values = [dv1]

                    arcpy.MakeNetCDFRasterLayer_md(inNetCDF, variable, x_dimension, y_dimension, nowFile, band_dimension, dimension_values, valueSelectionMethod)
                    print "success"
                    outname = outLoc + nowFile

                   arcpy.CopyRaster_management(nowFile, outname, +".tif","", "", "", "NONE", "NONE", "")

                else: print "DATA OUT OF RANGE"‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍
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13 Replies
MVP Frequent Contributor

So, what happens at the moment?

What errors are you getting or are you asking to validate this code prior to actually trying it?

I can see one problem with this :

arcpy.CopyRaster_management(nowFile, outname, +".tif","", "", "", "NONE", "NONE", "")

Shouldn't you add the "*.tif" to outname in the line above. Here the "*.tif" is the 3rd parameter. Which I am sure will not work.

Occasional Contributor III

Thank you. Output raster i am trying to save in tif format. I am getting following error massage. 

Message File Name Line Position 
 <module> D:\Arc-GIS-Python-Script\NetCDF_RASTER_TIME_SERIES.py 30 
IndexError: string index out of range 
MVP Esteemed Contributor

you had better throw a print statement in there to ensure that the negative slice doe indeed return the proper formatted year prior to testing.  you might want to split on "/" and return the last slice instead to get the year itself, rather than relying on a position count.

MVP Frequent Contributor

Never dealt with this sort of data before, but that error is obviously your indexing of the value in Nowfile.

>>> n = "dngthrysdfg"
>>> n[-12]
Traceback (most recent call last):
 File "<pyshell#5>", line 1, in <module>
IndexError: string index out of range

So, as Dan says, perhaps have a look at that variable before this step.

MVP Frequent Contributor

And, not sure what that [-12] is doing.

>>> n = "fkghthsyfgtrekh"
>>> n[-12]
>>> n[:-12]
MVP Esteemed Contributor
>>> a ='abcdefghijklmnopqrstuvwxyz'
>>> a[:-12]        # doubt it
>>> a[-12:]        # this one perhaps???????????
>>> a[-12]         # nope
MVP Esteemed Contributor

Any more info? or is this closed?

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Occasional Contributor III

Dan , Neil, i extremely sorry for the late reply, here holiday was going on . Problem still persist. by this command i am trying to extract selected time spam images. 

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MVP Esteemed Contributor

so you did see my example and you definitely want the first 12 characters of the string (line 4 in my example) and not the last 12 (ie line 4 in my example).  You need to print the string prior to extracting it so we know what is it is