grdcontour -Q: specify length instead of number of points
It looks like grdcontour does a contour length calculation and compares it to a minimum value under the hood (from grdcontour.c);
#define GRDCONTOUR_MIN_LENGTH 0.01 /* Contours shorter than this are skipped */
Contours shorter than a minimum length are not plotted. Would it be reasonable to also let the user specify a minimum length, in addition to the current -Q 'number-of-points' cut off?
I find that if you have the same grid, but different resolution, the -Q 'number of points' may have a big impact.
Pragmatic constructed example:
Plotting and extraction of the -2000 contour from a grid with three different resolutions (see contour_length.pdf)
- gebco_8m.nc - x/y increment 0.13333
number of points: N = 121
Length: 820 km
- gebco_8m_sampled.nc 1 - x/y increment 0.5
Number of points: N = 30
Length: 738 km
- gebco_8m_sampled.nc 2 - x/y increment 0.05
Number of points: N = 324
Length: 822 km
The number of points may be very different, but the length will roughly be the same (at least comparable). Wouldn't length be a nice additional way of specifying contour cut?