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- Windows Version
- Windows 10 64-bit (64.0 GB RAM - Intel Xeon W-2133 CPU @ 3.60GHz)
- Global Mapper Version
You can smooth the contours after they have been generated.
- Select them with the Digitizer Tool
- Right-click > Move/Reshape Feature(s) > Resample/Split Selected Features(s) at Specified Spacing
- Choose Sample Features at Fixed Distance Interval
- Enter the Spacing Distance e.g. 5 or 10 meters
- With the contours still selected Right-click > Move/Reshape Feature(s) > Smooth
By the way if you want to clip the SRTM to your boundary you can select the boundary be fore you select the online data source and choose the option at the bottom to Download Within the Currently Selected Polygon(s).
You can add 3D distance attributes to selected lines using Analysis/Measurement > Calculate Elevation/Slope Stats for Selected Feature(s) and choosing NO - Sample Terrain Along Path to get the 3D distance data from your terrain . Once added you can use the Feature Info Tool to get 3D distances or view the data via the Attribute Editor.
It may help to visualize what GM is trying to deliver when generating your contours. The image below is from your data where I have created a 0m user contour and compared it to your gridded surface when clamped out to a maximum elevation of 0m. What GM does is generate a reasonable contour along fragmented pixel data as shown. Therefore I assume that when you confine the process to a different area the second time around, that each contour might start at different points and therefore take slightly different routes than before. Note that your pixels are 10m and that you are generating 0.5m contours with it.