The USGS Seamless data (now part of The National Map) come in many different types of formats (e.g. ArcGrid, ERDAS IMG, or GridFloat), which you can use just like a regular Surfer .GRD grid file.
For example, you can download ArcGrid files. Extract all the files to your hard drive, and you can make contour maps directly from the ADF file. The steps are:
- Click Home| New Map | Contour.
- In the Open Grid dialog, select one of the ADF files and click Open.
- The contour map is created, just like it would be from any other grid file.
Note: Selecting any one of the ADF files in a USGS seamless data download folder will result in the same contour map. For example, selecting hdr.adf will result in the same map as selecting W001001.adf from the extracted USGS folder.
Updated October 25, 2018
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