DTM GENERATION OF THE OCEAN TIDAL TERRAIN 
USING PHOTOGRAMMETRIC TECHNIQUES, GIS AND GPS 
Christos Adamos Prof. Wolfgang Faig 
Photogrammetry & R. S. specialist Dean of Engineering 
Ypodomi Consulting Engineers Ltd University of New Brunswick 
Athens, Greece Fredericton, N.B, Canada 
Commission IV, Working Group 4 
KEY WORDS: Underwater Surface Mapping, Ocean Tidal Terrain, DEM/DTM, Non-metric, GIS, Relative Kinematic GPS. 
ABSTRACT 
Hydrographic Ground Truthing (HY-GRO) was a project currently carried out by the Ocean Mapping Group (OMG) at the 
University of New Brunswick. One of the purposes of this project was the investigation of the relationship between acoustic 
mapping data and the actual ocean seabed bathymetry. In order to facilitate the comparison, ground truthing information was 
generated in the form of DTM using stereo aerial photography of tidal areas at low tide. 
In this paper all aspects of the photogrammetric part of HY-GRO are discussed and generally the photogrammetric mapping of the 
tidal areas with the use of both metric and non-metric cameras is investigated. Small-format non-metric cameras were proven to be 
inadequate for tidal terrain mapping. Kinematic GPS was used for the establishment of ground control and it is found to be suitable 
for the tidal terrain both in terms of accuracy and speed. The DTM of a tidal area of Saint John Harbour was generated based on 
photogrammetrically collected data using the CARIS GIS. Perspective views, contour maps, colour-coded classifications of heights, 
slopes and aspects were produced from the DTM. Finally the accuracy of the DTM was also investigated and it is found to be in the 
magnitude of 16 centimetres. 
1. INTRODUCTION <> Bottom samples from cores and grabs. 
<> Physical samples. 
In November 1991, the Ocean Mapping Group (OMG) of the <> Terrestrial survey of the surficial geology. 
University of New Brunswick (UNB), Canada started a project <> Placement at known locations, of specially designed objects 
entitled Hydrographic Ground Truthing (HY-GRO). The of known shape, composition and acoustic properties. 
project was funded by a three year NSERC strategic grant and This paper deals with the determination of the sea-bed 
incorporates 23 organizations in Canada and U.S.A including topography by photogrammetric means. The required final 
universities, federal and provincial departments, and the U.S product was a Digital Terrain Model (DTM) of selected tidal 
Navy. The main objective was to investigate the relationship areas with an accuracy of 25 cm to be used as ground truthing 
between actual sea-bed characteristics (topography, information for testing the performance of the acoustic ocean 
composition and texture) and those obtained from acoustic mapping systems. 
measurements and to test the performance of various The tidal terrain is a special type of terrain that differs 
bathymetric systems. The Bay of Fundy was selected for this significantly from that of the mainland. Therefore the 
investigation because of its tidal ranges of up to 16 m, which topographic survey of the tidal areas poses some special 
allow sea-bed acoustic mapping from vessels at high water and difficulties. In this paper the use of photogrammetry for tidal 
physical and remote sensing sea-bed observations at low water terrain mapping is investigated by using both metric and non- 
levels. In particular, the three Canadian sites chosen were the metric cameras. It was decided to include a non-metric, small 
Saint John Harbor, Passamaquoddy Bay and Parrsboro format camera to investigate its suitability for tidal terrain 
Approaches. mapping and to ascertain whether economic gains can be 
Acoustic mapping data have been collected by the following realized by its use instead of an aerial metric camera. The use of 
acoustic ocean mapping systems installed aboard four vessels: relative kinematic GPS for the establishment of ground control 
<> Navitronics Seading sweep system. on a tidal terrain is also investigated. Finally the accuracy of a 
<> Simrad EM-1000 multibeam system with sidescan sonars. photogrammetrically generated DTM over tidal areas is 
<> Chirp Sonar subbottom profiler. established. Perspective views, contour maps, shaded relief 
<> SEISTEC high resolution subbottom profiler. representations, colour-coded representations of height, aspect 
<> Mesotech and Klein sidescan sonars. and slope classes were also produced based on the DTM. 
<> RoxAnn acoustic sediment classification instrument. 
<> Vertical beam echo sounder. 
<> Acoustic altimeter on BROWSER. 2. OCEAN TIDES 
Ground reference information has been collected using a variety 
of sensors. The actual sea-bed characteristics were determined Ocean tide is the response of the ocean to the periodic 
using: fluctuations in the tide-raising forces of the moon and the sun 
<> Stereo aerial photography. (Forester, 1983). It is a periodic phenomenon where the period 
<> Airborne remote sensing (Compact Airborne Spectrometer (T) is the time interval between successive low waters (LW) or 
Instrument) and Satellite remote sensing. high waters (HW). The range (R) of the tide is the height of the 
<> Underwater photography (BROWSER camera). high water above the low water (see Figure 2.1). 
18 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996 
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