Modelling subsurface lake bathymetry raster data using polygons in 3D

July 10, 2024

Ray Caron

In 2D, a raster is the best choice for visualizing lake bathymetric data when compared to the same features shown using contours, point clouds or polygons. But what type of feature works best in 3D?

Lake bathymetry data is typically gathered as point measurements, which are then interpolated into a raster or shown as contours for data visualization. When we want to port this data into an ArcGIS Pro 3D local scene, we’re faced with a question: how do we model lake bathymetry in 3D? Do we use rasters, points, lines or polygons?

If lake bathymetry were modelled using a DTM with bathymetry, where this DTM is added as a ground surface in 3D, then the lake bottom is the DTM surface (Figure A). We can use bathymetry data as a raster layer to add symbolization, but the visualization of the water surface is lost unless it’s recreated as a polygon feature.

A series of 3D lake bathymetry models, each modelling the same lake in a different way. The lake’s depth is represented using a spectrum of bright colours, with the deepest points in the lake being represented in purple, and red representing the shallowest areas. There are four models labelled “A”, “B”, “C” and “D”. Each model is described in more detail in the caption to this image.

From top to bottom: Figure A: Lake bathymetry modelled in 3D using a DTM with bathymetry raster added as 3D ground surface with a bathymetric layer raster for depth symbology. Figure B: Lake bathymetry modelled using point features and extruded in 3D. Figure C: Lake bathymetry modelled using contour lines and extruded in 3D, with a 2D raster. Figure D: Lake bathymetry modelled using polygons and extruded in 3D.

If lake bathymetry were modelled using points in 3D (Figure B), you’ll likely see slower map drawing times when changing your map perspective, as all of these dots need to be plotted individually. The result would be a dappled bathymetric surface.

If lake bathymetry were modelled using 3D extruded lines (Figure C), there would be a large improvement in drawing performance, as there would be many fewer features to draw compared to a point feature class. Visualization can be further improved by adding a 2D bathymetric raster. Aboveground, the model is easy to interpret and appealing, while bathymetry is shown as 3D contour lines in the subsurface.

If lake bathymetry were modelled using polygons extruded into 3D (Figure D), there would be a large improvement in drawing performance compared to a point feature class. Polygons also have the benefit of presenting a classified raster-like symbology as the polygons are adjacent to each other. Such a feature is easy to interpret and query. When viewing the bathymetry from the subsurface, the depth is accurately represented.

How to do it

The trick for converting a raster into a polygon lies in the contour tool. Run the tool using the raster as the input dataset, pick your contour interval and then choose contour polygons as the contour option. After you run the tool, add the resulting polygon layer to a 3D local scene. Then extrude the layer using the extrusion tool in the feature class menu. Don't forget to activate underground navigation in the ground layer setting for the 3D scene!

Where can I learn more?

As Esri-certified GIS instructors familiar with geoscience datasets, mining and exploration, we guide you through learning the essential geoscience workflows customized for the mining and exploration industry. Our Geospatial and Mining Geoscience using ArcGIS Pro course covers a wide range of ArcGIS Pro functionality including:

Creating a 3D subsurface geology model of sediment and bedrock;
3D interpolation of subsurface data and analysis;
Mining infrastructure suitability analysis;
Advanced geodatabase and feature class management using subtypes, domains and topologies;
Raster reclassification and analysis;
Sharing maps using ArcGIS Online; and
Creating map layouts and map series layouts.

Our Imagery Analysis in ArcGIS Pro course also covers a wide range of raster processing and 3D raster visualization.

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