What do you do when your topo survey meets water?
If you’ve ever needed to study water depths in a lake, river, or stream, then hydrographic surveys are they way to go. Seafloor Systems modern, survey-grade, sonar equipment for your on-water data collection needs.
As Trimble and Seafloor Systems experts, CSDS provides solutions that are:
- Compatible with Land Surveying equipment,
- Follow familiar Land Surveying workflows, and
- Easily produce powerful deliverables in common surveying file formats
Whether the deliverable you need is a topo (topography) map of water depths at certain intervals or a 3D point cloud of underwater surfaces, the Seafloor Systems range of hydrography solutions combined with Trimble Geospatial technology cover the range of precision positioning needed for your hydrographic or bathymetric applications.
Potential applications include:
- wildlife conservation projects (i.e. salmon habitat)
- water infrastructure inspections (canals, reservoirs, dams and piers)
- environmental studies
- water quality testing
- transportation projects
- detention pond volume
For example, accurate hydrographic data is used by hydraulic modeling software for flood risk management and hydrological risk assessment criteria. These models cover a wide range of activities including the planning, strategy and flood risk mapping for rivers, streams and channels. Seafloor’s products work by using sonar technology that calculates water depth at a 1% error tolerance, so that your relative error at 100 feet is about 1 foot.
Seafloor Systems Models
The HydroLite-TM echosounder is a single-beam sonar device that attaches to a manned boat or unmanned (either remote-controlled or autonomous) vessel. It sends and receives sound signals to mark the water depth at specific time intervals, while correlating the depth with a horizontal position from your synchronized/paired land surveying instrumentation.
The HydroLite is a combination of the Ohmex SonarMite portable echo sounder with a rugged clamp mounting and detail pole. The detachable frame provides support for the echo sounder, detail pole and either a robotic EDM prism or a GPS antenna (depending on the required configuration).
An important feature of the system is that the same positioning equipment and software are used throughout, enabling seamless integration of both hydrographic and conventional land survey data of the surrounding catchment area.
The HyDrone solution is an unmanned vessel with both remote-controlled and autonomous capabilities, which takes depth measurements using an attached HydroLite. The HyDrone system is a remote radio controlled survey platform suitable for hydrographic surveys when combined with the HydroLite portable echo sounder and a positioning system. Ruggedly constructed, the HyDrone and frame are made from high-quality marine components offering a lightweight, stable platform based on its twin-hull catamaran design.
The DFX echosounder is a multi-frequency echosounder. Similar to the HydroLite in form factor, it produces depth measurements using multiple frequencies – which can enhance hydrographic surveying in murkier water, shallower areas and when measuring seafloors that are composed of softer material.
Single-beam vs. Multi-beam
If you need georeferenced bathymetry points (basically topo on water), then you’ll have to choose between single-beam or multi-beam. Multi-beam packages are much more advanced and time-consuming. They also require hydrographic software packages instead of the standard Trimble land survey software commonly used for single-beam.
Most jobs done for private companies will only need single-beam work done. If you’ve done topo work before, then you won’t have any difficulty adding an echosounder to your setup.
Single-frequency vs. Dual-frequency
Single-beam echosounders come in two main categories:
Single-frequency systems such as our 200 khz Hydrolite-TM will give you “top-layer bathymetry.” If there’s heavy debris or vegetation underwater that’s resting on the floor of your lake or stream, then this system will identify the top of this material as your “depth.”
Our dual-frequency system has a 33 khz transducer along with the 200 khz transducer. Lower frequencies create more powerful sound waves from the system, allowing the 33 khz transducer to penetrate the “soft” top layer of your environment (typically 1-2 feet). This is NOT to be used to determine sediment thickness/volume.
It CAN be used to reach deeper locations (150 m range, instead of the 75 m range of the 200 khz transducer). It can also to determine (generally speaking) which areas are softer and which areas are harder.
You MUST be careful here, as many manufactures will claim that their low-frequency systems can determine the sediment thickness and the true hard-bottom of your body of water. The truth is, you need previously taken topo data of the hard-bottom or as-builts to compare with your current survey data in order to determine the thickness of the built-up material.
Once you have a system chosen and all of your planning in place, completing a hydro survey will take no more time than standard topo.
Data Capture Challenges and Solutions
Shallow water hydrographic surveys on inland waterways present unique challenges for data capture with overhanging tree canopies, bridges, siltation and vegetation presenting obstacles to gathering accurate data in a dynamically changing environment.
Conventional positioning technology using GPS is well-suited to open water situations such as estuaries, lakes and reservoirs, whereas robotic total stations present a practical solution to surveying in narrow rivers and streams. When used along with 3D scanners, hydrographic data can be combined in a point cloud of scanned topography including river banks and structures.
If specific steps aren’t followed, then communication errors are much more likely to occur between the Seafloor Systems equipment and the Trimble survey software. See the picture guide below for an example of a basic bathymetry survey setup. We have specific pairing documents for each type of software and in-depth manuals for our hydro equipment.
Contact Us Today!
If you think that hydrographic survey might be right for you, we can show you how to use your topo capabilities on the water.
Call CSDS at 800-243-1414 to ask a question, request a quote, or receive a product demonstration. One of our Surveying specialists will be in touch to share their expert opinion on which solutions will work best for your needs.
For more information on the topics mentioned above, send an email to firstname.lastname@example.org.