For example, to label the vector map with magnitude data, follow these steps:

1. Calculate the magnitude data and save to a data file format. 
   1. Click Grids | Calculate | Calculus.
   2. Click Browse in the Input Grid field, select your grid file, and click Open.
   3. Choose the Terrain Modeling | Terrain Slope command.
   4. Click the Change Filename folder icon in the Output Grid File field, and change the Save as type to DAT XYZ (*.dat).
   5. Click Save and OK.
2. Select the Vectors layer and click Home | Add to Map | Layer | Post.
3. Select the DAT file and click Open.
4. In the Properties window, make sure X=Column A and Y=Column B. Click the Symbol tab and choose an invisible symbol (if desired). Click the Label tab and and turn on the labels for Column C (the Z gradient data).

This method will label every grid node, which often produces too many labels to display. You can set the post map symbol frequency, but it may not be possible to get the data points and labels to coincide with the specified vector frequency, since the vector frequency is set separately for the X and Y directions.

There is not an easy way to post the labels only at each vector symbol when the X frequency and Y frequency are not set to 1. If you run into this problem where the labels and the vectors do not align due to the frequency, then you can use Grid Extract to extract data from the grid so that the frequency can be set to 1. 

For example, in the process outlined above, in step 1, save the results to a grid file instead of a DAT file. Then use Grids | Resize | Extract on both the original grid (used to create the vectors, saving the results to a grid file) and the magnitude grid (used to create the labels, saving the results to a data file). Then create the vector map from grid file (frequency = 1) and add a post layer from the data file.

This also works if you want to label the vectors with data from another grid. For example, if you created a vector map from one grid, and wanted to label the vectors with a grid file of slope % values (provided the slope % grid has the same grid geometry as the vector grid: XY extents and # of nodes), follow these steps: 

1. Select the existing vector layer in the Contents window and in the Properties window, on the Symbol page, note the X frequency and Yfrequency values.
2. Then click Grids | Resize | Extract and select the grid file used to create the vector map in the Input Grid field.
3. Set the desired frequency values under the Read Every column for the X and Y directions.
4. Click OK to save the extracted grid. Use this grid to create a new vector map (Home | New Map | Specialty | 1-Grid Vector Map). Make sure the X frequency and Y frequency values are set to 1 for the vector layer on the Symbol page in the Properties window.
5. Now that the vector map uses a frequency of 1 for the symbols, it is much easier to label them using Z values from another grid. To label the vectors with the Z from another grid, click Grids | Resize | Extract and select the grid file to be used as labels in the Input Grid field.
6. Set the same frequency value under the Read Every column for the X and Y directions.
7. Click on the Change filename folder icon in the Output Grid File field, and change the Save as type to DAT XYZ (*.dat).
8. Click Save and OK. This is the data file for the labels.
9. Select the vector map and click Map | Add to Map | Layer | Post.
10. Select the DAT file and click Open
11. In the Properties window, make sure X=Column A and Y=Column B. Click the Symbol tab and choose an invisible symbol (if desired). Click the Label tab and and turn on the labels for Column C (the slope % value). The labels are located at the vector origin.

There are a few other methods you could use to try and match up the labels to the vectors when the frequency of the vectors is not set to 1.

1. Another method is to work with the entire data set as above, and delete points that you don't want to post. You can delete the points from the source data file either manually or in a script. It is easy to manually pick points in a post map and delete the corresponding data points from a data file using the Map Tools | Layer Tools | Track Cursor command. Once the unwanted points are removed from the DAT file, you can reload the data file for the post map and the deleted points are removed from the map.
2. Another method is to create points at each vector manually with the Map Tools | Layer Tools | Digitize command or with a script. You can then save the XY coordinates of these points to a file. Then use Grids | Calculate | Calculus to create the gradient GRD file (as above), followed by Grids | Calculate | Residuals to calculate the Z value of those XY points. Once you have the desired X, Y and Z data, you can create the labeled post map.

Updated October 30, 2018