Satellite-Derived Bathymetry: Making Waves in GIS

Satellite-derived bathymetry, also referred to as SDB, is a method used to study the depth of a body of water from aerial imagery. While multi-beam sonar and airborne lidar are reliable techniques, collecting this data can be costly depending on the size and scale of the survey. On Episode 12 of the GEOTalks Podcast, we spoke with Amy Anfinrud from TCarta about their free global marine basemap and premium SDB data offerings in Global Mapper®.

What is Satellite Imagery?

Satellite imagery is a type of raster data, meaning it’s composed of pixels. Geospatial professionals rely on satellite imagery to make informed decisions about their work. GIS software, such as Global Mapper, is known for its ability to connect to online data sources, including free and premium satellite imagery, along with other datasets derived from aerial imagery.

If you’re focused on hydrography or coastal mapping, TCarta’s satellite-derived bathymetry product—known as the Global Marine Basemap—is free to use.

Types of Bathymetry Data

Whether you plan to stream data from an online source or perform a hydrographic survey, it can be helpful to understand the differences between bathymetric data types. Each type provides specific benefits to users:

• Satellite-Derived Bathymetry (SDB): A bathymetric product that provides depth information of near-shore waters from aerial imagery.
• Multibeam Sonar (MBES): This data is commonly collected from an AUV and can be used to provide a high-resolution visualization of underwater terrain.
• Airborne Laser Bathymetry (ALB): This bathymetric lidar product provides an efficient method for collecting data, though it has its limitations.

Satellite-Derived Bathymetry & GIS Software

In this episode of the GEOTalks Podcast, we discussed the value of TCarta’s Global Marine Basemap, in addition to their premium bathymetry products for GIS professionals. One of the most accessible ways to visualize satellite-derived bathymetry with GIS software is to create a topobathy map.

Create a Topobathymetric Map with Global Mapper

What is a topobathymetric (or topobathy) map? This technique enables users to create a continuous map representing both land elevation (topography) and underwater terrain depth (bathymetry). Global Mapper users can create a topobathy map using ALB, MBES, or SDB. For this scenario, let’s make a one from a DSM and TCarta’s Global Marine Basemap.

1. Load the Onshore Elevation Data & Marine Basemap

To start your topobathy map, head to Configuration in Global Mapper to set the projection to UTM. Then, load the onshore elevation data of your choice. For this example, I chose an elevation data source from the Popular tab of the Connect to Online Data tool—SRTM Worldwide Elevation Data and the World Topo Map.

Next, we’re returning to the Online Data tool to load the TCarta Global Marine Basemap.

2. Style Your Topobathy Map

Once your data is in the workspace, it’s time to style your topobathy map. If you’re planning to use the World Topo Map, you won’t have to configure much for the style. Instead, let’s check out the SRTM Worldwide Elevation Data.

When you select the SRTM layer in the Control Center, you will see options for Lidar/Terrain Display Controls. Here, you can set the shader—I chose the Global Shader—to fit your project and visualization needs. There are a number of built-in shaders to choose from; however, you can also customize them.

This visualization looks great; however, let’s say I also want a version with the World Topo Map, since it adds labels. It’s as simple as turning off the SRTM layer in the Control Center and turning on the World Topo Map layer!

What Bathymetry Data Should I Use?

The data you choose will depend on how you plan to utilize it. Multibeam sonar and airborne laser bathymetry are commonly used during hydrographic surveys and can result in high-resolution visualizations of your coverage area. For users who rely on both accuracy and precision in their data, MBES and ALB are a great option. However, depending on the overall scale of your survey, this data can come with a hefty price tag.

Satellite-derived bathymetry is a valuable alternative for visualizing nearshore bathymetry. Since SDB is produced from aerial imagery rather than a survey, users can access it without additional cost.

The International Hydrographic Organization wrote the Satellite-Derived Bathymetry Best Practice Guide to advise the hydrographic community on how to utilize this data best. In the foreword of this comprehensive guide, Mathias Jonas states, “[SDB] represents a potentially cost-efficient solution for covering very shallow waters. While SDB will not replace accurate acoustic or lidar survey(s) due to its known limitations, it can be used with great effect if those uncertainty constraints are well understood and managed.” It’s reassuring to know that there are alternatives to map depth without breaking the bank.

Listen to the GEOTalks Podcast & Get Involved

The GEOTalks Podcast highlights the work of GIS professionals and enthusiasts worldwide. Want to learn more about mapping the coast and other unique places? Check out more from the GEOTalks Podcast:

• Join our GEOTalks Podcast community on LinkedIn
• Subscribe on your preferred listening platform to listen to episodes on the go: Spotify, Apple, and YouTube
• Get involved with GEOTalks by emailing us at marketing@bluemarblegeo.com
• Connect with Amy Anfinrud at: amy@tcarta.com

References

B-13 Edition 1.0.0 International Hydrographic Organization…, International Hydrographic Organization, iho.int/uploads/user/pubs/bathy/B_13_Ed100_032024.pdf. Accessed 6 Nov. 2025.