Abstract
The NASA Ames Stereo Pipeline (ASP) is an open source software of
automated geodesy and photogrammetry tools to process satellite, aerial
camera, and historical imagery with and without accurate camera pose
information using a structure-from-motion (SfM) methodology. ASP is
designed to generate topographic digital surface models (DSM). We added
to the ASP topographic module a bathymetric module to derive near shore
bathymetry using satellite panchromatic bands (PAN), and multispectral
bands. The process is semiautomatic and can generate either topographic,
bathymetric or topo-bathymetric (TB) seamless 3D point clouds and DSM in
the same vertical and horizontal coordinate systems. The bathymetric
results depend heavily on the water surface elevation and while previous
methods considered the water surface horizontal, our bathymetric module
takes into consideration the earth curvature for the considered
satellite imagery. A land / water mask can be automatically derived
using NIR bands or can be user defined. The new ASP bathymetry module
was tested using WorldView-2 panchromatic and green band stereo imagery
in Florida Keys (Key West) FL from May 2015. The nearshore PAN and GRN
bathymetric results around Key West, FL were validated against
bathymetric lidar collected in 2017. The validation errors improve with
adding camera calibration and finally alignment to prior topographic
lidar data (no bathymetry data used) from 1.0778 m root mean square
error (RMSE) to 0.4052 m RMSE to 0.2480 m RMSE, respectively. For PAN
bands the depth penetration around Key West was around 4 m with a TB DSM
resolution of 1 m. For the same area, using the green (GRN) band the
bathymetric validation RMSE in absence of camera adjustment or alignment
was 1.1040 m, with camera adjustment RMSE improves to 0.6846 m, and with
topographic alignment RMSE is 0.5854. For the green bands the depth
penetration in Key West was approximately 7 m with a TB DSM resolution
of 2 m.