topic Re: Areal precipitation using IDW in Mapping Questions

Areal precipitation using IDW

PV1 — Mon, 09 Sep 2013 06:03:10 GMT

I have got the following problem. I have a catchment and several gauging stations measuring daily precipitation amounts. I would like to interpolate the precipitation amounts from these stations (points) to the whole catchment. In the next step I would like to calculate average precipitation value for the catchment. I can do it for one day (1 value for each station).
The problem is that I have 30 years of daily precipitation measurements in each station and so I need to do this process thousands of times. I have created a simple model in model builder which could do this process once, but I am not able to force it to do it repeatedly.

I need help how to automate this process.

Thanks

IDW automation

PV1 — Mon, 09 Sep 2013 06:04:04 GMT

Re: Areal precipitation using IDW

CPoynter — Mon, 09 Sep 2013 22:06:15 GMT

You will need to create a loop or iteration process to go through each or of your daily records. There are iteration tools in ModelBuilder or maybe export to python and code the iteration/loop process.

Regards,

Craig

Re: Areal precipitation using IDW

KundanDhakal — Fri, 20 Sep 2013 18:18:15 GMT

You will need to create a loop or iteration process to go through each or of your daily records. There are iteration tools in ModelBuilder or maybe export to python and code the iteration/loop process.

Regards,

Craig

Any example Craig that you would like to provide here?

I am also stuck in same condition. Iteration in model builder does not clearly mention using fields within the same shapefile/ table (each field is a measurement for a day in my case). I think examples are not clear too. If I need to use IDW and iterate across multiple fields how would I set up the model builder? Attached is the screenshot of the attribute table of the shapefile I plant to iterate.

[ATTACH=CONFIG]27643[/ATTACH]

Re: Areal precipitation using IDW

CPoynter — Sat, 11 Dec 2021 17:57:26 GMT

The critical part you need to manipulate is the field names. Access to these can be achieved using:

import arcpy
tbl= arcpy.ListFields(r'D:\Temp\Test.mdb\Test')
for fld_names in tbl:
     print fld_names.name

import arcpy
tbl = r'D:\Temp\Test.mdb\Test'
fld_names = [f.name for f in arcpy.ListFields(tbl)]
print fld_names

Second method many by more ideal for iterating in a script, as field names are stored in a python list/table.

Regards,

Craig

Re: Areal precipitation using IDW

KundanDhakal — Sat, 11 Dec 2021 17:57:28 GMT

Thanks Craig for your quick response. I figured out that I need to use ListField. I am struggling figuring out the correct syntax. I found a python script to iterate IDW on ESRI Forum but that script was written for ArcGIS 9.3. I've recently upgraded to 10.2 and I think the scripts are now not compatible.

I would be really grateful if you could provide further help.

--kundan

The critical part you need to manipulate is the field names. Access to these can be achieved using:
import arcpy
tbl= arcpy.ListFields(r'D:\Temp\Test.mdb\Test')
for fld_names in tbl:
     print fld_names.name
or
import arcpy
tbl = r'D:\Temp\Test.mdb\Test'
fld_names = [f.name for f in arcpy.ListFields(tbl)]
print fld_names
Second method many by more ideal for iterating in a script, as field names are stored in a python list/table.

Regards,

Craig

Re: Areal precipitation using IDW

CPoynter — Sat, 11 Dec 2021 17:57:31 GMT

Without testing it myself, try:

import arcpy
from arcpy import env
from arcpy.sa import *

arcpy.CheckOutExtension("Spatial")

env.workspace = 
srcFC =
cellSize =
power =
searchRadius = 

tbl= arcpy.ListFields(srcFC, 'r*')
for zField in tbl:
    print 'Processing: ' + zField

    outIDW = Idw(srcFC, zField, cellSize, power, searchRadius)
    outIDW.save(env.workspace + '\\' + zField + '_IDW')

del srcFC, cellSize, power, searchRadius, tbl, zField

You will need to set your input workspace, source featureclass, cellsize, power, radius.

You will need to have a look at the 10.2 Help reference to IDW, so you can identify which Radius method you wish to utilise.

What I have given here is a basis for development, which needs to be polished and finished to run for your application.

If it doesn't run in IDLE, run from within Python GUI in ArcGIS or ArcCatalog.

Regards,

Craig