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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
BATHYMETRIC EXTRACTION USING WORLDVIEW-2 HIGH RESOLUTION IMAGES 
M. Deidda “, G. Sanna “ 
? DICAAR, Dept. of Civil and Environmental Engineering and Architecture. — University of Cagliari, 09123 Cagliari, 
Italy - (mdeidda, topoca)@unica.it 
Commission VIII, WG VIIL/4 
KEY WORDS: Bathymetry, Underwater, Satellite, WorldView2, High resolution, Imagery, Stereoscopic, Accuracy 
ABSTRACT: 
The fundamental principle underlying the methods used to extract bathymetric information from remote-sensed imagery is that 
different wavelengths of the solar light penetrate the water body to different depths. In order to extract bathymetric values from 
multispectral satellite imagery we implemented the Jupp method (Jupp, 1988), in IDL language and integrated it in the ENVI menu 
structure. In this experiment we apply this method to two images of the Poetto beach in Cagliari (Sardinia, Italy) acquired from the 
new-generation WorldView-2 sensor. Launched in October 2009, the WorldView-2 sensor provides, among others, one (named 
Coastal) that was designed specifically for this kind of analysis; we chose to use the Coastal band in place of the Blue one when 
applying the model. The images (a stereoscopic pair) were acquired on June 17, 2011. The 5419 scene was pre-processed in order to 
separate the sea bottom classes. This class was then georeferenced to overlap on the 5318 scene. A traditional bathymetric survey 
was performed, up to 1,50 m, planned and carried out in order to calibrate the model. For each scene, 10 calibration areas were 
selected, and for each of them a digital model of the sea bottom was generated. Precision and accuracy of the method were evaluated 
by analyzing the results extracted from the stereo-pairs and by examining the correlation between the surveyed depth values and the 
calculated ones, between the different models calculated from the same scene using different calibration areas, and between the 
models obtained from the two images. 
1. INTRODUCTION 
Since 1984, launch date of the Landsat 5 satellite, whose 
imagery was used for the first bathymetric mapping from 
satellite images, the technology has advanced in strides. In the 
last decade, the construction of high resolution sensors such as 
Ikonos and Quickbird allowed for ever more accurate analysis. 
Still, to date it's not yet possible to evaluate the precision of the 
model, but only to estimate the achieved accuracy by comparing 
the digital models extracted from the imagery with actual 
bathymetric surveys. 
The technique for extracting bathymetric information from 
satellite imagery is becoming widespread, to the point that the 
WorldView 2 satellite sensor was designed with a dedicated 
band named “Coastal”. One method for obtaining the precision 
of the procedure is comparing the results from independed 
images acquired at the same time. The fact that WorldView2 
can produce stereo pairs where the component scenes are 
acquired in a short time interval thus makes possible to evaluate 
the precision of the results. 
For the purposes of this research it was chosen as a test area the 
Poetto littoral. Located on the southern coast of the island of Figure 1. Distribution of the Areas of calibration in the 5318 
Sardinia (Italy), the Poetto is the beach of the city of Cagliari, Scene 
Whose urban area surrounds it. Its geographic position has 
determined its history: it was always subject to erosion 
phenomena, mostly of anthropic origin, and for this reason in 
2002 it underwent a beach nourishment intervention with sand 
collected from the sea. 
The evaluation of accuracy was performed by comparing the 
depth values extracted from each scene, between the different 
scenes and with the bathymetric survey. 
In each scene, 10 different deep water areas of 50x50 pixels 
were selected and used to calibrate the model. The distribution 
of the calibration areas in the two scenes is shown in Figure 1 
and Figure 2.