tides-compare v3.2.3¶

Mercurial revision 5770:c90c3015e72d | 2026-05-22

Description¶

tides-compare is a tool for statistically comparing the barotropic tidal harmonics of a reference file against one or more additional files. It specifically looks for the Ha (amplitude) and Hg (phase) variables in each file.

The comparisons are computed for:

The entire domain.
Regions deeper than 500 meters.

Usage¶

tides-compare [OPTIONS] file1 [file2 ...]

Options¶

Option	Description
`-h`, `--help`	Display this help message and exit.
`-o <file>`	Specify the output file for the comparison results. If not provided, a default name (`vector-difference.nc` or `<wave>.vector-difference.nc`) is used.
`-b <file>`	Specify the bathymetry file (must contain a `z` variable). If not provided, the default file `/home/softs/genesis/data/topography/data/gridone.grd` is used.
`-w <wave>`	Specify the tidal wave to compare (only one wave is supported at a time).
`-c <file>`	Path to a tide gauges MGR file to compute statistics at specific points.
`-p <file>`	Path to a polygon file defining the working area for the comparison.
`-z <zone>`	Deprecated. Name of a pre-set zone (no longer supported).

Examples¶

Basic Comparison¶

Compare tidal harmonics between two files:

tides-compare file1.nc file2.nc

Compare with Custom Output File¶

Save the comparison results to a custom output file:

tides-compare -o my_comparison.nc file1.nc file2.nc

Compare for a Specific Tidal Wave¶

Compare the M2 tidal wave between two files:

tides-compare -w M2 file1.nc file2.nc

Compare Using a Custom Bathymetry File¶

Use a custom bathymetry file for depth-based filtering:

tides-compare -b my_bathymetry.grd file1.nc file2.nc

Compare at Tide Gauge Locations¶

Compute statistics at specific tide gauge locations:

tides-compare -c tide_gauges.mgr file1.nc file2.nc

Compare Within a Polygon Area¶

Restrict the comparison to a specific polygon-defined area:

tides-compare -p my_polygon.txt file1.nc file2.nc

Full Example with All Options¶

tides-compare -o M2_comparison.nc -b custom_bathy.grd -w M2 -c gauges.mgr -p area.poly file1.nc file2.nc

Environment Variables¶

tides-compare does not rely on specific environment variables. However, ensure that:

Input files (NetCDF, bathymetry, MGR, polygon) are accessible.
Output directories have write permissions.

Notes¶

Input Files:

Must contain Ha (amplitude) and Hg (phase) variables for tidal harmonics.
The first file is used as the reference for comparison.

Bathymetry:

If -b is not specified, the tool uses the default bathymetry file: /home/softs/genesis/data/topography/data/gridone.grd.
Depth-based comparisons (e.g., h > 500m) are computed using the bathymetry data.

Output:

The output file contains:
- Norm of the complex difference (a).
- Amplitude difference (G).
- Phase lag difference (in degrees).
- Complex error statistics.
Statistics are computed for:
- The entire domain.
- Regions deeper than 500 meters.
- Regions deeper than 1000 meters.
- Tide gauge locations (if -c is used).

Tide Gauges:

The MGR file must be in a format compatible with the tool (e.g., lon lat pairs).

Polygon:

The polygon file defines the spatial area for the comparison. Points outside the polygon are excluded.

Deprecated Options:

The -z option (pre-set zones) is no longer supported.