Grid from Server
Click the Grids | New Grid | Grid from Server command or the 
button to download data from an online web mapping server and create a new grid file. Clicking the Grid from Server command opens the Download Online Grids dialog.
The Download Online Grids dialog can also be accessed from the Open Grid dialog by clicking Download. The downloaded grid will be used to create a grid-based map layer or in the following grid command dialog, depending on which command was used to open the Open Grid dialog.
When using the Download Online Grids dialog, a server with appropriate data must be selected. Surfer currently supports four types of servers, web mapping server (WMS), Open Street Map server (OSM), web coverage server (WCS), and web feature server (WFS). WMS, OSM, WCS, and WFS servers provide different types data. WMS and OSM servers are generally used to create base maps with the Home | New Map | Base | Base from Server command.
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When selecting a WMS or OSM server, an image is downloaded to be used as a grid file.
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If there are no Z values associated with the image, when the image is used as a grid file, a value between 0 and 1 is assigned to each pixel in the image based on the color of that pixel, this color-based gridding approach may not produce meaningful results for all image types.
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A few WMS servers do contain elevation data that can be converted for use in a grid. Examples of these include:
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Worldwide | Physical and Topographic Maps WW | E-Atlas
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Worldwide | Physical and Topographic Maps WW | USGS Worldwide Shaded Relief
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North and Central America | Physical and Topographic Maps NA | USGS 3DEP Elevation
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WCS servers download data values that are directly used as a grid file.
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WFS servers download vector data (points, polylines, and/or polygons). Because of this, they cannot be used with the Grid from Server command.