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I am having trouble getting SNODAS data, downloaded from the ftp, to display properly in ArcGIS Pro.

I've tried following NSIDC instructions from How do I import SNODAS data into ArcGIS? to create a proper header file. After creating the header file, it can add that .dat file to the map, and in the Contents pane it looks like it's loaded correctly (displays a color ramp with appropriate values), but nothing actually shows up on the map.

Any suggestions?

EDIT: Ok I think I've found at least part of the problem

If I do a "zoom to layer" on the SNODAS data, it brings me to the rendered data. However, it appears as if something is wrong with how its being projected...

I'm new to ArcGIS so apologies if this doesn't make any sense. When I zoom to the SNODAS layer and move the mouse around, there is a little display at the bottom that shows the location of the mouse. The units are displayed as meters, but they should be degrees lat/lon. For example, if i move my mouse to the left-most extent of the raster, it tells me I am about 125 meters West, but it should be 125 degrees West, i.e. the western extent of the continental USA

2 Answers 2

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Firstly, a useful way of examining a study area is to zoom to a layer's extent in the display. This method is a quick and easy way of zooming in to the area of concern.

So, if the layer is not showing up on the map first step is to check by zooming in to the layer.

Now, coming to the primary concern that the data is in meters and you want them to be displayed in degree decimals, and for that, you need to understand the concept of Coordinate systems, projections, and transformations

  1. Use the project Raster tool in ArcGIS Pro to Transforms a raster dataset from one coordinate system to another

  2. In the tool set the Output Coordinate system to a desired Geographic Coordinate System

  3. Add the output and observe that the coordinate values are in the Geographic Coordinate system

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  • Thank you! I am still having issues though. When I try to use the project raster tool, it needs me to define an input coordinate system. The raster is unprojected as is, but digging around the internet I think I should use WGS84 here. Specifically, I chose "WGS_1984_ARC_System_Zone_13", since I'm doing analysis in Colorado For output coordinate system, I chose NAD 1983. It then needs me to choose a "geographic transformation", and "WGS_1984_(ITRF00)_To_NAD_1983" seemed like the best choice. After all of this, the output raster does change, but still just a speck in the middle of the ocean
    – hm8
    Dec 11, 2020 at 17:58
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So, as it turns out, the provided SNODAS raster has an undefined coordinate system. I was able to solve this problem by using the Define Projection tool to define the corodinate system as GCS NAD 1983

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