Surfer 6 used a different algorithm to smooth the contour lines in a contour map, so opening any SRF file that was saved in Surfer 6 with this smoothing option enabled into Surfer 7 or higher will be smoothed differently. This difference is expected.
If you want to retain the contours shown in Surfer 6, there are a couple things you could do:
- You could export the map from Surfer 6 as a raster image (TIF, BMP, JPG, etc.) or a vector DXF file and import it into the newer version of Surfer as a base map.
- You could smooth the grid file itself, not just the contour lines. This will make any map created from this grid file in any version of Surfer look the same. Smooth the grid file by clicking Grids | Edit | Spline Smooth or Grid | Matrix Smooth (Surfer 6) prior to creating the contour map.
Updated October 15, 2017