Visualisation¶

bathy provides a range of visualisation functions for bathymetric data. All plot_* functions return (fig, ax) so you can annotate, save, or compose figures.

Elevation maps¶

Basic bathymetry¶

bathy.plot_bathy(data)

Uses the cmocean deep colormap (light = shallow, dark = deep).

With contours¶

# Specific contour depths
bathy.plot_bathy(data, contours=[-200, -1000, -2000, -4000])

# Number of contours
bathy.plot_bathy(data, contours=10)

Custom colormap¶

bathy.plot_bathy(data, cmap="viridis")

Bathymetric analysis¶

Hillshade¶

bathy.plot_hillshade(data, azimuth=315, altitude=45)

Slope¶

bathy.plot_slope(data)

# Clip extreme values
bathy.plot_slope(data, vmax=20)  # Cap at 20 degrees

Curvature¶

bathy.plot_curvature(data)

Positive values indicate convex features (ridges), negative indicate concave features (valleys).

Bathymetric Position Index (BPI)¶

bathy.plot_bpi(data, radius_km=2.0)

BPI identifies ridges (positive) and valleys (negative) relative to the surrounding terrain. The radius_km parameter controls the neighbourhood size.

Aspect¶

bathy.plot_aspect(data)

Aspect is the downslope direction a surface faces (0° = north, 90° = east, 180° = south, 270° = west), following the standard GIS convention. Uses a circular colormap so north is consistent at both ends of the scale. Flat areas are shown as NaN.

Rugosity¶

bathy.plot_rugosity(data, radius_km=1.0)

# Clip extreme values
bathy.plot_rugosity(data, vmax=0.05)

Rugosity (Vector Ruggedness Measure) quantifies terrain complexity. Values range from 0 (flat) to 1 (maximally rough). Higher values indicate structurally complex seabed — useful for identifying hard substrate and reef habitat. The radius_km parameter controls the neighbourhood size.

Geomorphons¶

bathy.plot_geomorphons(data, lookup_km=2.0)

# Finer scale with tighter flatness threshold
bathy.plot_geomorphons(data, lookup_km=1.0, flatness_threshold=0.5)

Geomorphons classify topography into 10 morphological forms (flat, peak, ridge, shoulder, spur, slope, hollow, footslope, valley, pit) by comparing each cell to eight neighbours at the lookup distance. Colours follow a warm (elevated) → grey (neutral) → cool (depressed) scheme. The lookup_km parameter controls the scale of analysis; larger values capture broader landscape forms.

Overview (all maps)¶

# All eight bathymetric analyses in one figure
bathy.plot_overview(data)

# Custom neighbourhood scales
bathy.plot_overview(data, bpi_radius_km=2.0, rugosity_radius_km=2.0, geomorphons_lookup_km=5.0)

Displays bathymetry, hillshade, slope, aspect, curvature, BPI, rugosity, and geomorphons in a single 4 × 2 figure. Useful for a quick scan of all key bathymetric characteristics.

Depth zones¶

Classify bathymetry into depth zones:

# Default zones: shelf, slope, abyss, deep
bathy.plot_depth_zones(data)

# Custom zones
bathy.plot_depth_zones(
    data,
    zones=[0, -200, -2000, -6000],
    labels=["Shelf", "Slope", "Abyss", "Hadal"],
)

Statistical plots¶

Histogram¶

bathy.plot_histogram(data, bins=100)

Hypsometric curve¶

bathy.plot_hypsometric_curve(data)

3D surface¶

bathy.plot_surface3d(
    data,
    stride=10,                 # Downsample factor
    vertical_exaggeration=50,  # Z-axis scaling
    smooth=5,                  # Optional smoothing
    elev=30,                   # View elevation
    azim=-60,                  # View azimuth
)

Contours on any plot¶

All plot functions support the contours parameter:

bathy.plot_hillshade(data, contours=[-200, -4000])
bathy.plot_slope(data, contours=5)
bathy.plot_depth_zones(data, contours=[-200, -1000])

Saving figures¶

fig, ax = bathy.plot_bathy(data)
fig.savefig("bathymetry.png", dpi=300, bbox_inches="tight")