FindNearestCpoint

Find nearest C-point

Introduction

GETM curvilinear bathymetries include information on both corner points and central (C-) points. The C-points of the bathymetry coinside in the horizontal with the pressurepoints (T-points) of GETM.
For pre- and post-processing it is often advantageous to find the point in the bathymetry, which is closest to a particular position. For curvilinear coordinates, this is not a straight-forward process. The present python script (find_nearest_cpoint.py).

This can be convenient for instance to find locations for the scatter utility, or processing to nesting.

Usage/example

bjb@swell$ python find_nearest_cpoint.py --latval=52.20 --lonval=1.66 --latname=latc --lonname=lonc topo.nc
Looking for target point as (lon,lat)
Reading input nc-file topo.nc
Creating geoide to compute distances
Making great circle computations (inverse geod lookups)
Nearest point found at index (0-based/C-style):
(i,j) = (186,117)
(lat,lon) = (52.199957,1.660139)
Note that the distance to point is 11 m
ncks should confirm with e.g.
ncks -H -d xic,117 -d etac,186 -v lonc,latc topo.nc
All done OK