Gridding high numbers of data points in Surfer, especially when those data points lie along lines (like digitized contour lines), can sometimes cause irregular contour lines.
You can try one of these methods to smooth the map and remove artifacts:
- Thinning out the data so there aren’t quite as many data points along the lines. If you are digitizing the data points from an original contour map that you are trying to recreate, please see some hints on point spacing in the attached newsletter article, Issue37Didger.pdf, and also the online article Recreating Hand Drawn Contour Maps using Didger and Surfer.
- Changing the gridding method and/or options (e.g. including the Anisotropy value).
- Reducing the number of grid nodes in the grid file.
- Using Grids | Edit | Spline Smooth after the grid has been created to smooth the grid and remove some of the artifacts.
- Using Grids | Edit | Filter with a low-pass filter to remove background noise from the grid.
- If there are just a few areas, you can click File | Open and open the grid in the Grid Editor and modify the Z values of certain grid nodes. Save the grid and recreate the contour map.
Updated January 19, 2017