[OC] A Topobathymetric Map of the Hawaiian Islands Visualization

What This Visualization Shows

This data visualization displays "[OC] A Topobathymetric Map of the Hawaiian Islands" and provides a clear visual representation of the underlying data patterns and trends. The visualization focuses on Hey everyone, I recently graduated from the GIS: Cartography and Geovisualization program at COGS. I thought I'd post one of the thematic projects I was most proud of: a topobathymetric map of the main Hawaiian Islands.

If you're interested, you can read more about the project and see higher-resolution imagery here:

https://www.alexhordal.ca/portfolio/hawaii-seafloor-to-summit

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The topobathymetric surface used in this map was derived from a mosaic of multiple DEM sources, including the NOAA NCEI Coastal Relief Model (CRM) (\~30 m) and ETOPO2022 (\~450 m), as well as multibeam bathymetry from SOEST’s Hawaiʻi Mapping Research Group (\~50 m). The CRM provides nearshore coverage, ETOPO2022 provides global bathymetry, and the multibeam data contribute higher-resolution detail where available.

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Due to differences in spatial resolution and coverage, all datasets were resampled to a common 90 m grid to balance detail, continuity, and visual consistency across the surface. Source datasets reference differing vertical datums, resulting in minor elevation offsets; however, these differences are negligible at the 90 m resolution used in this map and do not affect overall terrain representation.

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A key design consideration was the symbolization of the merged DEM using a custom, continuous, diverging colour ramp that seamlessly blended topography and bathymetry at mean sea level. This involved extensive experimentation with colour stops, positioning, transparencies, and manual classification intervals. Hillshading and slope highlights were applied to accentuate geomorphology and improve terrain interpretation, particularly below the ocean surface.

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Bathymetric and terrestrial features were identified and labelled, including points of interest, population centres, summits, volcanoes, seamounts, and underwater landslides. Subtle typographic hierarchy and placement were also used as visual depth cues to accentuate the pseudo-3D terrain effect.

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The map also includes several small contextual snippets highlighting major features and important historical events, an 8.5× vertically exaggerated elevation profile of Mauna Kea to reinforce the seafloor-to-summit narrative, and an inset map of the Hawaiian Archipelago for location context.

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​, which allows us to understand complex relationships and insights within the data through visual storytelling.

Deep Dive into the Topic

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