nav[aria-label="Primary Navigation"] { padding: 0; & ul { list-style: none; width: 100%; display: flex; flex-direction: row; justify-content: start; align-items: start; gap: 30px; padding: 0; & li { margin: 0; } & ul li { list-style: none; } } }

Calculate average values from observations within a distance weighted by the square of the inverse distance

ZHIZUO

I have a shape file for U.S. county centroid, and another shape file for temperature point observations across the U.S.

I'd like to calculate the average temperature for each of the county centroid, from the temperature observations within a certain distance of the centroid, weighted by the square of the inverse distance. Could anyone let me know which tool(s) should I use to get this outcome? Thanks very much in advance.

Alec

Find more posts tagged with

Accepted answers

AbdullahAnter

I updated the model as row 03 in Dan reply.

I think that what you want, isn't that?

you can download it in attachments.

TempartureModel.tbx.zip

All comments

NeilAyres

"weighted by the square of the inverse distance", distance to / from what?

Wouldn't just a simple IDW interpolation of the temperature points, then get the average for each county be good enough?

DanPatterson_Retired

besides the math issue trying to obtain county level information from country level data is a very poor mix of data source scale. Have you explored the possibility that data may be available at the county level, or at worse, the state level?

AbdullahAnter

You can do that with model builder,

Just add two fields in U.S. county centroid Feature class, the first field you will calculate a certain distance (weighted by the square of the inverse distance).the second field for average temperature values but you will let that field Null

then run buffer tool using the distance field.

select by location for all temperature point observations within each polygon

use summary statistics tool to get average

get this value and make field calculate in the second field that you created

you will use iteration selection, to do that for each polygon buffer.

thanks

ZHIZUO

Hi Neil, it is distance from a county centroid to any temperature point that is within a certain distance of the centroid, say 100 kilometres. I think IDW interpolation creates a raster layer. Then zonal statistics could get an average value for a county. But this is still different from what I intend to do. Thank you for your reply.

ZHIZUO

Hi Dan, thank you for your reply. I am using temperature as an example. I also need to get many other variables. But there is no available county level data.

ZHIZUO

Hi, Abdullah, your suggestion is very good. I am new to GIS so need to explore a bit how to use model builder to get this done.

But for the first distance field, what should be entered at first? I am not sure what a certain distance means. I will need all the temperature points within 100kms of a county centroid. Does it mean the first field needs to be 1/10000?

Thanks again for your reply.

AbdullahAnter

Is the distance 100 km for all centroid county or it is varies ?

ZHIZUO

It is fixed at 100km radius for every county centroid.

AbdullahAnter

The model is ready.

Just you should add field for average temperature to county centroid shape file before use the model.

you can download the model in attachment

and the picture below for model design

Export Graphic.png

TempartureModel.tbx.zip

ZHIZUO

Hi Abdullah, thank you so much for this. I will try this next Monday. Will let you know how it goes.

AbdullahAnter

You will find two model

First for none weighted Just( mean temperature)

Second for weighted by the square of the inverse distance with the following equation:

Sqr (1 / Distance ) * temperature value

ZHIZUO

I think the model is working. It has been a few hours and it is still running. I have over 4000 temperature points and over 3000 county centroids. This is probably why it takes so long.

And just to make sure, the second is weighted by the inverse of distance squared -- (1/distance*distance), not the inverse of square root of distance -- 1/sqrt(distance), right? I saw you had them both above.

AbdullahAnter

I updated the model as row 03 in Dan reply.

I think that what you want, isn't that?

you can download it in attachments.

TempartureModel.tbx.zip

ZHIZUO

Thank you so much! Yes, this is what I want.

ZHIZUO

Hi Abdullah, the computer finally completed the calculations. But it seems that only the not_weighted tool worked while the weighted tool didn't work. After the calculations, the added field (the average temperature field in the tool) is still all zero. I tried the tool in a sub-sample of my data and it still did't work. Would you mind trying it as well and let me know where I went wrong? I have attached my working files here. The log file is for the weighted tool that didn't work. Thought it might help too?

tem90.7z.zip

arizona_centroid.7z.zip

log.txt.zip

AbdullahAnter

No Zhi Zuo , this is the weighted according to your Expression:

Do it manual and you will see that the zero is logical number according to previous Expression

First select by location for temp90 that with in a distance 100 km for any Arizona centroid as the following picture:

Then, calculate a distance for a round points using Near tool as the following picture:

Now, add field (Double) and calculate the square of the inverse distance as you and Dan agree

1 /( distance * distance )

and it will be so small number close to zero , so ArcGIS write it in the field as zero

look for the picture:

so it is so logical that if you multiply Zero for Temperature value will equal zero too.

Join the Conversation

Signed in members can post, follow updates, and more. New here? Register a free account.

Quick Links

Community Help
Find useful guides, FAQs, and documents to help you navigate and make the most of Esri Community.