Underwater Topographic Survey of a German Lake with the Apache 4 Pro USV
2026-07-30
In the forest around Bartenstein in Germany, a survey team needed an underwater topographic map of a small freshwater lake, without moving a large crewed boat into a protected natural site. Working from the shore, they mapped the lakebed with the CHC Navigation Apache 4 Pro unmanned surface vessel carrying an HQ-400 multibeam echosounder, and produced the finished map the same day. This is how the survey came together.
The site: a freshwater lake in the forest
The survey site is a freshwater lake set in the woodland around Bartenstein. The water body is about 180 metres long and 90 metres wide, with a maximum depth of roughly 6 metres. The work was part of a water resource investigation, so the team needed an accurate record of the lakebed shape across the whole basin.
The survey site is a freshwater lake in the forest near Bartenstein, Germany, where the team prepares the Apache 4 Pro USV on the shore.
The challenge: mapping the lakebed without a large boat
The goal was a clear deliverable, an underwater topographic map of the lake, but the setting made a traditional survey difficult:
A large survey vessel is awkward to transport to a forest lake and hard to launch into the water.
Chartering a boat and crewing it adds significant cost to a small survey.
The site sits in a protected natural area, so the team needed low-impact equipment that would not disturb the environment.
What the team wanted was a compact, lightweight platform that two or three people could carry and operate, paired with a data workflow fast enough to turn the field survey into a finished map quickly.
The solution: the Apache 4 Pro USV with the HQ-400 multibeam
The team paired the Apache 4 Pro, a compact unmanned surface vessel, with the HQ-400, a compact multibeam echosounder built for shallow-water bathymetry. The USV is small enough to carry to the water and launch by hand, so no trailer, ramp or crewed boat is needed, and its low-impact operation suits a protected site. Field acquisition ran in the on-board survey software, which drives the vessel and logs the multibeam soundings live as it covers the lake.
Live acquisition on the lake: the HQ-400 builds a dense multibeam swath of the lakebed, shown over the satellite base map with real-time depth, attitude and position readouts.
In the field: on the water in 8 minutes
On site, the team assembled and checked the equipment on the shore in about 8 minutes, completing the pre-launch installation and setup before the vessel entered the water. From there the Apache 4 Pro ran its survey lines across the lake while the HQ-400 recorded a dense swath of depth soundings, building full coverage of the lakebed rather than a set of single-point measurements.
From data to map: processing in 20 minutes
The field data was processed in the CMS software, with post-processing completed in about 20 minutes. The team exported the result as a LAS point cloud, then brought it into Global Mapper and overlaid it on a satellite base map to produce the finished underwater topographic map of the lake. The result gave the water resource investigation an accurate, full-coverage picture of the basin.
The Apache 4 Pro covered the lake on planned survey lines in autonomous mode, recording continuous depth across the basin before the data was processed into the finished map.
The value: lighter, faster, lower cost surveys
Running the survey from a compact unmanned platform removed the cost of chartering and crewing a boat, kept the footprint on a protected site to a minimum, and still delivered the full-coverage underwater topographic map the project needed. For repeat work on lakes, reservoirs and other inland water bodies, that mix of easy transport, fast setup and quick processing is the core benefit of a USV based bathymetric workflow.
Crewed boat vs Apache 4 Pro USV at a glance
Consideration
Large crewed boat
Apache 4 Pro USV with HQ-400
Transport and launch
Trailer and ramp, hard to reach a forest lake
Carried in by hand, launched from the shore
Cost
Boat charter plus crew
No boat charter
Team and handling
Larger crew
Two to three people
Site impact
Higher footprint on a protected area
Compact, low-impact operation
Setup time
Longer mobilisation
About 8 minutes on the shore
Processing
Longer office turnaround
About 20 minutes to a finished map
For teams planning inland bathymetric surveys, the wider range of CHC Navigation marine surveying solutions covers USV platforms and multibeam payloads for hydrographic and bathymetric work.
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About CHC Navigation
CHC Navigation (CHCNAV) develops advanced mapping, navigation, and positioning solutions designed to increase productivity and efficiency. Serving industries such as geospatial, agriculture, machine control and autonomy, CHCNAV delivers innovative technologies that empower professionals and drive industry advancement. With a global presence spanning over 140 countries and a team of more than 2,200 professionals, CHC Navigation is recognized as a leader in the geospatial industry and beyond. For more information about CHC Navigation [Huace:300627.SZ], please visit: https://geospatial.chcnav.com/about/overview
