Solutions to: "The entire grid was assigned NoData" error when Assigning NoData to a grid in Surfer

There are a few possible reasons for getting an error that the entire grid was assigned NoData.

Reason 1: The vector base layer contains a polyline instead of a polygon.

Check to be sure that the vector base layer contains a polygon. To check this:

1. Click Home | New  Map | Base.
2. Select the vector file and click Open.
3. In the Contents window, expand the Base(vector) layer. Does it contain a polyline or polygon?

If it contains a single polygon, then this is not the problem. If it shows a single polyline, even a “closed” polyline, then this is the problem. If it shows a single polyline, then you can follow these steps if you are using a BLN file:

1. Click File | Open in Worksheet, select the BLN file and click Open. It opens in the worksheet.
2. Select row 2 and click Home | Clipboard  | Copy.
3. Scroll to the bottom of the file, and select the first blank row and click Home | Clipboard | Paste.
4. Increase the number in cell A1 by 1 (it is the number of points).
5. Click File | Save and File | Close.

Now assign NoData to the grid with this BLN file.

Reason 2: The vector file contains multiple polygons.

It could be that there is still more than one polygon in the vector file. To check this:

1. Click Home | New  Map | Base.
2. Select the vector file and click Open.
3. In the Contents window, expand the Base(vector) layer. There should just be one polygon in the base layer. Is that the case? 

If you are using a BLN file where there are multiple polygons (and you are blanking outside each of them), then you can follow the steps in the knowledge base article: I want to blank outside several polygons on a map in Surfer, but the entire map gets blanked, resulting in a horizontal planar grid.

If you are using another type of vector file for the vector base layer, you can select all of the polygons in the vector base layer and combine them into a single, complex polygon by clicking Features | New Features | Combine.

Reason 3: The grid and the vector file use different coordinates.

If the grid file and the vector file are in different coordinate systems, then this could cause the error. To check this:

1. Click Home | New  Map | Color Relief.
2. Select the grid file and click Open.
3. Click Home | New  Map | Base.
4. Select the vector file and click Open.
5. Separate the maps on the screen slightly by clicking on one map and dragging it away from the other map. Verify that the coordinates on the axes of the base map are fully within the coordinates on the axes of the contour map.

If the vector file is located outside the extents of the grid file, you could get this error, as expected. The grid file and the vector file need to be in the same coordinate system for the blanking to work successfully.

Reason 4: The polygon in the vector file is completely within the grid nodes of the grid file.

This is not very common, but in some cases the grid file resolution is so coarse, there are simply no grid nodes within the polygon boundary in the BLN file. Therefore, when blanking outside the boundar, all the grid nodes are blanked. To check this:

1. Click Grids | Edit | Convert, select the grid file and click Open.
2. In the Save Grid As dialog, choose to save the grid as a DAT XYZ (*.dat) data file, give the file a name and click Save.
3. Click Home | New Map | Post, select the data file you just saved and click Open.  A symbol is posted at each grid node.
4. Select the Post layer in the Contents window.
5. In the Properties window on the Symbol page, set the Symbol size to something smaller, like 0.020, so you can see the individual symbols (which represent grid nodes).
6. Click Home | Add to Map | Layer | Base, select the vector file and click Open. That overlays the polygon on top of the post layer.
7. Verify that at least one grid node (one symbol on the post layer) is within the polygon boundary. If not, then this is the problem.

If that does not help, please email the grid file and the vector file to surfersupport@goldensoftware.com.

Updated December 2021