topic Creating a Raster from Centroid Point Data in Geoprocessing Questions

Creating a Raster from Centroid Point Data

OnaStrikas — Wed, 11 Sep 2013 15:25:56 GMT

Hi all,

I have WRF climate model output data that I am trying to rasterize in Arc. The WRF cells are 3km x 3km in this scenario, and WRF gives me the latitude and longitude of the centroid of each cell. Upon trying to rasterize this point data set, I cannot manage to create the same grid WRF is using because it appears ArcGIS auto populates the cell with no manual override.

This grid also has to be not running North-South by angled at about 330 degrees. This second capability I have not been able to find in Arc. I have tried using Point to Raster as well as creating my own raster with the known bounds of the grid, but I run into one or bothe of the problems described. You can see what I am talking about in the image below. [ATTACH=CONFIG]27354[/ATTACH]

Has anyone here created a raster with an angled (non North-South) orientation? How is it done?

I am using ArcInfo 10.0.3 build 2414, and have all possible extension rights.

Thanks for any help!

Ona Strikas
PhD Student
Dept of Geology
UNC- Chapel Hill

Re: Creating a Raster from Centroid Point Data

curtvprice — Thu, 12 Sep 2013 05:11:44 GMT

I have WRF climate model output data that I am trying to rasterize in Arc. The WRF cells are 3km x 3km in this scenario, and WRF gives me the latitude and longitude of the centroid of each cell. Upon trying to rasterize this point data set, I cannot manage to create the same grid WRF is using because it appears ArcGIS auto populates the cell with no manual override.

If you want a grid to line up with the WRF grid, you will need to work in a coordinate system that lines up with the WRF grid coordinate system. Your decimal degree locations in your screen shot are being plotted in some other coordinate system (maybe UTM?).

Has anyone here created a raster with an angled (non North-South) orientation? How is it done?

Raster cells are aligned with xy directions of the raster's coordinate system-- normally with square cells. There's no such thing as an "angled" grid, though you can project data on the fly to display it that way (with on the fly resampling). I think that's what is being done in your screenshot with the "angled cells" that are displayed.

I'd read this:

Desktop 10.0 help: What is raster data?

Re: Creating a Raster from Centroid Point Data

markdenil — Thu, 12 Sep 2013 14:06:07 GMT

In my experiance, modelers often have no idea what coordinate system their models use.
I have had to create points from their raster cells (in an 'unknown' coordinate system)
preserving not only the lat and long data the cells provide, but also the x and y position of the cell in the original raster.

Withe the lat and long positions, I can plot the points in geographic space
(and project it to projected space) and use it as I wish. I assume that this is what you do, too.

But, because I have also preserved the original x and y locations
(lower left = 1,1 and upper right = max x, max y)
I can go back in the other direction (known projected or geographic space to model space)
by using an insert cursor to build new points (with the new attributes I have added)
using the original x and y locations.
This gets the points back in the proper places in unknown space to make an orthogonal raster from them.

It is a bit roundabout, but if one don't know the model coordinate space
or if the model coordinate space is one not supported in Arc,
it works.