Spatial referencing netCDF to Raster images

2022
5
01-10-2013 05:23 AM
JoelDavis
New Contributor
Hello,

I'm fairly new to arcGIS and am trying to create some raster images from datasets of the ocean floor, showing how their depth has changed throughout time. I downloaded a series of text files from the earthbyte.org website and converted them to grid format (NetCDF files) using GMT using instructions on the readme. I then used used the "Make NetCDF raster layer" tool in Arcmap (10) to create a series of individual raster images, which worked fine.

The issue I'm having is how to spatial reference them. As far as I can tell from the website, the data should be projected in WSG1984, however the rasters I have just display as having an unknown projection. Additionally, I've tried to re-project the images to WSG1984 using advice from other forums, however, this hasn't worked.

I'd be grateful if anyone could give me some tips or point out where I'm going wrong.

Thanks,

Joel
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5 Replies
JulieEkstrom
New Contributor II
I had the same problem!
Here's the note that someone posted on my plea for help last week:

"I was having a similar problem. I used the Make NetCDF Raster Layer tool to create a couple of rasters (SST data), and it imports and projects fine, but no spatial reference. I tried using the "Define Projection" tool in ArcToooolbox within ArcMap and from within Catledog, all works fine, big green flashing tick, but still no spatial reference!? But get this, if you right click the raster in Catalog and then edit the Spatial reference, and choose appropriate projection, it works... go figure... another Arc-mystery."

His post is at this: http://forums.arcgis.com/threads/74063-netCDF-to-feature-raster-problems?p=265033&posted=1#post26503...

hope that helps.

julie
JUSTINEFEDERICI
New Contributor

This post from years ago has saved me tonight! Thanks!

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markdenil
Regular Contributor II
If there is no georeference at all, you have to georegister the data.
I have a image I output from a netCDF that has the useful coordinates of:
<Extent>
Top>   0.5
Left>-0.5
Right>8240.5
Bottom>-2996.5
clearly just a cell center pixel count.

The simplest ploy is to figure out the coordinates for the corners and use these easy-to-identify features to do the georegistering.
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louise_acou
New Contributor II

I have this same problem as you. I can set the projection, but that doesn't help. The lat/lon of my data in the netcdf are in UTM, and I'm guessing this is part of the problem. I could easily find the coordinates for the corners but how would I apply these to do the "georegistering"?

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DavidAskov1
Occasional Contributor

Did anyone ever solve this? If so, please post a solution!

I used this process: 

- Make NetCDF Raster Layer tool

- Copy Raster tool to GeoTIFF

- gdal_translate -co PROFILE=BASELINE in.tif out.tif       (strips all tags)

- created a TFW file and dropped it in the same folder

- manually defined the coord sys in ArcCatalog

As if this wasn't a bad enough workflow, as mentioned above, the define projection tool seems to have no effect. That means I have to do the last step manually in Catalog, and I'm trying to automate this. 

Any ideas? thanks.  

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