TDOT 3 GREENTDOT 3 NIR
Use in ALB alternative method
Airborne Laser Bathymetry (ALB) is a manned aircraft technique that uses a green laser to survey the topography under water. However, ALB is difficult to implement quickly and inexpensively, and because it measures from a ground elevation of 400m or more, it can only provide a low-density laser point cloud of about 8 points/m2 over land and about 1 point/m2 underwater.
The accuracy of the elevation values is also limited.
On the other hand, TDOT 3 GREEN enables surveying from lower altitudes of 150m or less, so that the geometry of onshore river banks and the topography of the riverbed and the shape of trees in the river channel can be accurately reproduced with a high-density point cloud of more than 100 points/m2.
Photographs of conditions at time of survey
Both ALB and drone green laser survey data visualize the riverbed and riparian forest.
However, drone green laser surveying can reproduce trees precisely enough to be able to identify tree species from their shapes.
Enlarged view of cross section
With TDOT 3 GREEN, the surface and bottom of the water tend to be clearly defined.
Cross-sectional view
Bird’s-eye view
Example of surveying an area of 2 km in extension.
Bird’s-eye view
Density
TDOT 3 GREEN allows surveying at higher densities than ALB.
*The time taken for surveying is different.
TDOT 3
ALB
Noise
The generated noise data are equal.
*The time taken for surveying is different.
TDOT 3
ALB