Equipped with a tape measure, an ice auger, a jug of water, a Lowrance HDS-5, and their best thermal ice-fishing garb, they set out to test the mapping capabilities of Lowrance and ciBioBase through 11.5" of ice on an stormwater detention pond in Blaine, Minnesota.
|Lance Hoff of Momentum Environmental prepares one of five sites for ground truth measurements of sonar through ice, sonar through a drilled hole, and hand measured depth|
|Water was poured onto the ice prior to logging .sl2 sonar data in order to achieve bottom acquisition through the ice|
After about an hour of data collection in this manner, the SD card with the logged pond data were uploaded to ciBioBase. Approximately 10 minutes later contour, vegetation biovolume, and bottom hardness maps were processed, complete with water volume summary statistics. The data were ready for export and comparison with the other test datasets!
|One foot bottom contours produced with ciBioBase processing of Lowrance .sl2 data collected through the ice. An ice thickness and water elevation offset was applied to the data.|
|Vegetation biovolume (% water column filled with vegetation) and bottom hardness maps (red = hard, tan=soft)were simultaneously created along with bottom contours|
The table below shows some interesting results. First, depths from the Lowrance HDS-5 were remarkably accurate and precise compared with actual depth measurements taken with the tape measure. The largest difference found was approximately 3" (which may have been due to the tape measure sinking that far into the muck). These findings are consistent with other verification research published in this blog showing Lowrance HDS producing highly accurate and precise depth measures in a variety of environments.
|Results from 5 verification sites where holes were drilled and depth was compared with a tape measure (hand measure), sonar through open water, and sonar through the ice. Differences between the measures (subtraction) are also presented|
These findings demonstrate the power and flexibility of the ciBioBase system for rapid inventorying and monitoring of stormwater retention basins.