One of the most frequently asked questions by BioBase EcoSound users is, “how far apart should I space my transects for creating maps?” Although as always, the most appropriate response is: “it depends,” we still offer solutions below that cover the most common use case scenarios. We thank our partners at NC State University Department of Crop Science for contributing useful data from Waccamaw Lake in North Carolina USA.
Full Bay/Lake Map on a Large Lake
|Transects can be designed in ArcMap using the Fishnet Tool in the ArcToolbox (see BioBase Support & Resources). In this case, 200 m transects perpendicular to the longest shore with one nearshore loop was created. The total length of transects in this instance equaled 189 km (117 mi) and would take 23 field hrs to map driving 8 km/h (5 mph). ESRI Shapefiles or Google Earth .kml path files can be converted to .gpx for your Lowrance Chartplotter. Convert the Trail to a Route and let out Outboard Autopilot do the mapping for you!|
Follow up, intensive surveys in areas of interest
|Zoomed in area near boat launch where an invasive aquatic plant species was located during initial BioBase mapping surveys. Follow-up intensive surveys were carried out to more precisely map infestations.|
Mapping small bays and fingers? Try concentric circles
Situational awareness – mapping vegetation edges
|Get the smoothest bathymetry with a concentric circle transect design|
Situational awareness – dealing with extremely steep slopes
Situational awareness – mapping small patches
|Patch of hard bottom (brick red on map) in an otherwise soft-bottom lake (light tan). Surveyor noticed double echo on sonar chart while mapping and diverted course to methodically cover hard patch and thus more precisely map its extent.|
We hope this gallery of images and explanations can help BioBase users make the most efficient use of their time on the water mapping and produce the best possible aquatic habitat map! For more information search this blog, aquatic resource mapping user forum, or contact us at firstname.lastname@example.org.