topic Loop conditional in raster calculator in Python Questions

Loop conditional in raster calculator

BennyIstanto — Thu, 05 Dec 2019 03:23:46 GMT

Hello,

I have daily rainfall data in milimeters in GeoTIFF format with naming convention chirps_YYYYMMDD.tif (example chirps_20100101.tif), and I also have 1 raster of dry-spell with name dslr_chirps_20091231.tif and both raster have same spatial resolution and extent.

Then I would like to calculate dry-spell for 1 Jan 2010, IF(rainfall>1,dslr=0,dslr+1). Using raster calculator I can use this formula: Con("chirps_20100101.tif" > 1, "dslr_chirps_20091231.tif" == 0, "dslr_chirps_20101231.tif" + 1)

The raster output will be dslr_chirps_20180101.tif

Problem:
I have 10 years daily rainfall data and would like to calculate daily dry-spell for all the available data period.

How to loop the above calculation using model builder, when the output for each calculation will use as input for the next calculation?

Re: Loop conditional in raster calculator

JohannesBierer — Fri, 10 Dec 2021 23:39:19 GMT

I don't know how to do this in the model builder - but with python maybe you could define your input data and output with the following code?

It's from: datetime - Iterating through a range of dates in Python - Stack Overflow

from datetime import timedelta, date

def daterange(start_date, end_date):
    for n in range(int ((end_date - start_date).days)):
        yield start_date + timedelta(n)

start_date = date(2009, 12, 31)
end_date = date(2010, 12, 31)
for single_date in daterange(start_date, end_date):
    
    d = single_date.strftime("%Y%m%d")
    
    d1 = single_date+timedelta(days=1)
    d2 = d1.strftime("%Y%m%d")
    
    input1 = "DSLR_CHIRPS_{}.tif".format(d)
    input2 = "CHIRPS_{}.tif".format(d2)
    output = "DSLR_CHIRPS_{}.tif".format(d2)

    print("{} - {} - {}".format(input1, input2, output))‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: Loop conditional in raster calculator

BennyIstanto — Thu, 05 Dec 2019 10:45:38 GMT

Thank you for your reply, I will try it.