1. Click Home | New Map | 3D Surface | 3D Surface, select the grid file and click Open. The surface map is created.
2. Click the 3D Surface layer in the Contents window to select it.
3. In the Properties window, click the Mesh tab.
4. Check the check boxes in the Draw lines fields under Lines of Constant X and Lines of Constant Y.
5. Adjust the Frequency so you can see as many wire mesh lines as you wish.
6. If you do not want to see the colors on the surface,
   1. Click the General tab.
   2. In the Upper field in the Material Color section, click the Custom colormap (...) button.
   3. Enter 0 in the Opacity field and click OK.

One advantage of the surface map over the wireframe map is that you can choose the frequency of the mesh lines (every line, every other, every 5th, etc.). Another advantage is that you can set the map limits for a surface map, which you cannot do for a wireframe map. Additionally, surface maps don't show blanked areas, where wireframe maps do. On the other hand, wireframe maps are vector images (not bitmap images), so the resolution may be better than for surfaces maps. 

 3D Surface map v. 3D Wireframe map of a blanked version of the Diablo.grd sample file.

Updated December, 2021