Networking 3rd Party GPS/GNSS into Lowrance

Ray Valley

Aquatic Biologist and BioBase Product Expert

I frequently get inquiries from current and prospective BioBase users about the accuracy of consumer-grade Lowrance GPS and whether survey-grade 3rd party receivers capable of differential correction (DGPS) or receiving positions from multiple satellite constellations (Global Navigation Satellite System – GNSS) could be used with Lowrance and processed with BioBase.

The first question about accuracy prompted a test in March of 2013 with a Lowrance HDS tested side-by-side with a Trimble GeoXH.  I was pleased to find less than 1m deviation on average from post-processed Trimble DGPS positions.  One meter accuracy and precision is typically sufficient for most boat-based mapping applications. Still, prerequisites for some projects require DGPS, and there are a number of BioBase users who have and still would prefer to have DGPS generated positions to use when logging trips. Thus, I was interested in exploring the capabilities of networking positions from a third-party receiver into a Lowrance HDS.

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Mapping Hidden Channels with Genesis Live

River channel thalwegs (the line of lowest elevation within a valley or watercourse) are often dynamic, and sometimes hidden features of large river systems.  Especially low slope or impounded systems.  The thalweg is a critical geomorphological feature of river and reservoir systems and affects everything from sediment transport, to fisheries habitat, to algae or invasive plant control.

Thus a good bathymetric contour map is a necessary pre-requisite for effective river and reservoir management.  Here, we walk you through how to use new real time technologies (C-MAP’s Genesis Live) to produce smooth, precise, and accurate maps of hidden river thalwegs all within one trip to the site and with automated post-processing with BioBase’s EcoSound.  We’ll use an annotated image gallery to take you through this process.

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Guest Blog: Correlations between EcoSound Biovolume and Aquatic Plant Biomass

Andrew W. Howell and Dr. Robert J. Richardson
 
North Carolina State University; Dept. Crop and Soil Sciences
 
Why do we want to sample submersed vegetation biomass using sonar?

Invasive aquatic plants, such as non-native hydrilla (Hydrilla verticillata), negatively impact waterway systems in the southeastern United States and on a global scale. Often, these aquatic weed species impede recreational activities, power generation, and disrupt native ecological systems. Costs associated with aquatic weed management include expenses accompanied with monitoring, mapping, and implementing control measures. Prompt detection and accurate mapping of submersed aquatic vegetation (SAV) are critical components when formulating management decisions and practices. Therefore, SAV management protocols are often reliant upon the perceived extent of invasion. Traditional biomass sampling techniques have been widely utilized, but often require significant labor inputs, which limits repeatability, the scale of sampling, and the rapidness of processing. Advances in consumer available hydroacoustic technology (sonar) and data post-processing offer the opportunity to estimate SAV biomass at scale with reduced labor and economic requirements.

The objectives of this research were to document the use of an off-the-shelf consumer sonar/gps chartplotter to: 1) describe and characterize a relationship between hydroacoustic biovolume signature to measured hydrilla biomass; 2) develop algorithm for on-the-fly assessment of hydrilla biomass from interpolated biovolume records; 3) define seasonal hydrilla growth patterns at two NC piedmont reservoirs; and 4) create a visual representation of SAV development over time. From these objectives, the expected outcome was to describe a protocol for passive data collection while reducing the economic inputs associated with labor efforts involved in biomass sampling and post-processing evaluations. In our research, a Lowrance HDS-7 Gen2 was utilized to correlate biomass from monospecific stands of hydrilla within two different North Carolina piedmont reservoirs using BioBase 5.2 (now marketed as EcoSound – www.biobasemaps.com), cloud-based algorithm to aid in post-processing.

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Interpreting bottom hardness in shallow lakes and ponds: digging deeper into the data

BioBase’s EcoSound bottom composition (hardness) algorithm has become quite popular for researchers and lake/pond managers to determine where sedimentation from the watershed may be occurring.  However, interpreting sonar returns in shallow environments (e.g., less than 7 ft or 2 m) with off-the-shelf sonar is challenging, especially if aquatic vegetation is present.  Each situation is different and the objective of this blog is to inform you of how to interpret your EcoSound map in situations when you encounter counter intuitive bottom hardness results.

Here are some high level points to remember.

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FAQ of the year: Does BioBase EcoSound Map Sediment Depth?

Thanks to advances in physical, chemical and biological technologies and funding that are focused on reducing sedimentation or muck depth in waterways, many water resource practitioners are eager to determine how much sediment is in a waterway of interest and how much could be removed. As such, we frequently are asked: “Will BioBase tell you how deep the sediment is?”

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BioBase EcoSound does Seagrass, Kelp, and Tides Too!

Although BioBase EcoSound was originally developed for aquatic vegetation mapping in inland lakes, users along both US Coasts have helped us diversify its toolbox to now be a powerful coastal habitat mapping tool as well!

One of the biggest challenges of mapping coastal habitats is their tidal influence with depths changing harmonically based on the moon phase and other factors.  Fortunately, however, widespread tide stations and large public databases of tide predictions allow for accurate and precise offsets to georeferenced and time-stamped sonar logs from Lowrance HDS or Elite units uploaded to BioBase EcoSound.  BioBase EcoSound immediately queries the nearest tide station to your upload (up to 75 km) and adjusts your depth and seagrass or kelp biovolume to the Mean Lower Low Water (MLLW) datum every 5 minutes.  Tidal statistics (Avg., start, stop, high, low,) are archived in your account for each trip.

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How BioBase is Helping Fish Conservation

BioBase EcoSound is helping State Fisheries Departments and Research Institutions across the US and UK to better manage Fisheries by providing important information about fish habitat.  See below for a short description of these ongoing investigations.Precision bathymetric mapping to estimate concentrations of a fish toxin (rotenone) to kill invasive fish in a Nebraska backwater lake. … Continue reading “How BioBase is Helping Fish Conservation”

BioBase EcoSound is helping State Fisheries Departments and Research Institutions across the US and UK to better manage Fisheries by providing important information about fish habitat.  See below for a short description of these ongoing investigations.

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Helpful Lowrance Hints: Depth Tracking

We promote BioBase as an automated “easy-button” solution for creating aquatic maps, but unfortunately, mobile acoustic data collection is not something you can push a button and forget about and expect perfect results.  Like using most other sophisticated instrumentation, users need to monitor that the instruments are performing as expected and sometimes make adjustments if they aren’t.

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Using Insight Map Creator to view Photos and BioBase maps on your Lowrance Chart

Few may know about a powerful GIS conversion tool that will convert virtually any spatial file into a format (.AT5) viewable on your Lowrance Chartplotter.  And best of all, it’s free!  Insight Map Creator is one of several of Navico’s GoFree products available at www.gofreemarine.com. Here you can register for a free GoFree account and download the IMC software.  There are lots of examples and tutorials about how to convert vector and raster GIS data to .AT5 digital charts that are covered in the documentation folder that won’t be repeated here.  Rather, we’ll walk you through two applications that many BioBase users will find extremely valuable.

Display HD ArcMap Aerial Imagery GeoTiffs on your Lowrance HDS chart

Add Basemap Imagery and zoom into a high resolution (in this case 1:15,000) area of interest so that shoreline detail can be seen (e.g., think about the zoom level you want when using the chart on the water).  Project Dataframe into WGS84 World Coordinates.
In the Data View, export (File – Export) a high res (≥ 300 dpi) image as .TIF and write a .TFW world file.  Pan the map and export slightly overlapping snapshots (same zoomlevel and resolution) so that IMC can stitch together a mosaic.  Small ponds and lakes will probably require only one aerial shot, large systems like the Guntersville example shown will require many.

Simple User Interface of GoFree’s Insight Map Creator (IMC).  Run the x64 .exe program after downloading and unzipping. Select Raster Mode from the View menu.  Use a fine resolution (at least 1 meter per pixel) to get shoreline detail. If your source data only covers one resolution and you want your final map to represent this specific resolution, you have to set Min and Max resolution to the same value. If your source data covers more than one resolution, you set the Min Resolution to the resolutions of your most detailed images and the Max Resolution to your least detailed image. Make sure that your source images match the resolution steps as close as possible to minimize the loss of quality due to the re-sampling process.  Add the folder where the source files can be found, specify where the created AT5 files should go, then click “Build.”  A successful build should show a folder containing “Bound AT5s.” Consult the documentation with your download for more specific details about the process and other advanced settings.
Get your HDS Chartplotter ready to import AT5 imagery
  1. Make sure your Chart has “Shaded Relief” selected (Chart Options on Lowrance HDS)
     2.   Insert a MicroSD card with all .AT5 files saved to the card.  Select Photo Overlay (Full) in the Chart Options

Screen capture of a successfully loaded HD aerial image overlain with other navigational aids included in HDS basemaps.  Use aerial images as navigational aids, and to target fishing or sampling areas (e.g., partially submerged timber, or in the top example “Guntersville Grass”)

Create a HD image of vegetation biovolume coupled with an aerial photo.


The process we describe can be used to create any spatial image for your HDS.  So, if you wish to reproduce the HD map you see on your PC in BioBase as a chart in your Lowrance, just follow the steps outlined in your Support & Resources in your BioBase account (Creating Publication Quality Imagery) and the steps outlined above.

EcoSound Aquatic Vegetation heat map (% aquatic plant biovolume) as seen in BioBase.
Aquatic vegetation heatmap data exported from BioBase, imported into ArcMap and converted to a raster .TIF following “Creating Publishable Quality Imagery” BioBase tutorial and then converting the exported .TIF to .AT5 using GoFree’s free Insight Map Creator (see directions above).  Researchers or anglers can use these vegetation maps to strategically target sampling or fishing areas.

BioBase Helps Manage Honeoye Lake Macrophyte Harvesting Program

Guest Blog By Terry R. Gronwall, Chairman of the Honeoye Lake Watershed Task Force (Honeoye, NY)
Honeoye Lake is one of the smaller (~1,800 acres) Finger Lakes in Upstate New York.  We have been managing our macrophyte population by using a harvester for about 25 years.  The objective of our harvesting program is to both provide relief for the recreational lake users and to remove biomass containing phosphorus from the lake every summer.  We average around 800 wet tons of biomass removed per season.

When we learned about ciBiobase we saw this service as a way to make our macrophyte harvesting operation more efficient by concentrating our efforts on areas in the lake that have macrophytes growing through most of the water column.  This is shown as the red zone on our macrophyte maps.  We plan to monitor our actual harvesting rates relative to our macrophyte maps over the summer harvesting season to see if we achieve our goal of increased productivity.

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