overlap, we will have to read a set of three shapefiles, extremum,
outermost_contour and max_speed_contour, containing several
snapshots. We do not want to re-read field indices for each snapshot.

Rename u, v to ugos, vgos in NetCDF files.

vgos, lon to longitude, lat to latitude.

Add a test for successive_overlap with periodic grid.

Add snapshot for region 4 at a different date, in input files, for a
new test of successive_overlap.

read_snapshot and successive_overlap instead of a named constant of
module successive_overlap_m.

Bug fix in main programs test_read_snapshot and
test_successive_overlap: take into account that step is in degrees.

0ce6b1b4.

Write extr_map in test_read_snapshot since extr_map has been
defined. So create a procedure write_extr_map because now we want to
write extr_map both in test_local_extrema and in test_read_snapshot.

Preparing to take into account periodicity in successive_overlap: add
argument periodic to read_snapshot and extend s%extr_map in longitude
if periodic.

In program extraction_eddies, constraint on max_radius(1) is necessary
only if periodic.

Make read_snapshot more general: add argument step.

In procedure get_snapshot, remove definition of s%number_eddies
because this is already done in read_snapshot.

Promote dist_lim from local constant of successive_overlap to constant
of module successive_overlap_m because we need it in read_snapshot
(and test_successive_overlap and test_read_snapshot).

(instead of date_index = 1). This is the value read from the NetCDF
files. We have to increase the width of field date_index to 5 digits
(4 digits would only allow approximately 30 years since 1950).

In procedure read_snapshot, check that all input eddies have the same
date index, and return it as an additional argument.

Assume that the input NetCDF files contain a single date.

In program test_set_all_outerm, do not write file
"isolated_nodes_1.csv". Since s is defined by set_all_outerm only, all
the eddies are necessarily isolated.

hard-coding them.

Remove component twice of type eddy, no longer needed.

>= 0 everywhere outside of procedure local_extrema.

In test Nearby_extr, use output from Get_snapshot_region_1_noise since
we now use suff_amp in extremum shapefile.

GPC_F and GPC must be used.

read_snapshot, assert that there is no duplicate tuple in
s%ind_extr. Since we are not sure of that, we must use a do construct
and not a forall in order to define s%extr_map.

Bug fix in program test_local_extrema: support missing values. Add
corresponding test.

Output s%ind_extr in program test_read_snapshot.

be useful for testing successive_overlap.