REMOTE SENSING OF POLAR REGIONS USING LASER ALTIMETRY 
Beata M. Csatho and Toni A. Schenk 
Byrd Polar Research Center and Department of Geodetic Sciences and Surveying 
The Ohio State University 
Columbus, OH 43210 
email: csatho @ohglas.mps.ohio-state.edu 
Robert H. Thomas 
Code YS, NASA HQ 
Washington, DC 20546 
William B. Krabill 
Laboratory of Hydrospheric Processes 
NASA/Goddard Space Flight Center 
Wallops Island, VA 23337 
Commission I, Working Group 3 
KEY WORDS: Mapping, DEM/DTM, Data Integration, Laser Altimetry System, Change_Detection 
ABSTRACT 
The vast ice sheets of Antarctica and Greenland cover almost 10% of the Earth's land surface. Together with sea ice they have a sig- 
nificant influence on local and global climate. Moreover, the mass balance of the polar ice is a sensitive indicator of global climate 
changes. There is a growing concern that some ice fluctuation may occur at a rapid rate with an associated effect on the global sea 
level. Thus it is imperative to monitor the ice sheets on a global scale, assess their mass balance, and predict their future behavior. 
This paper reports about studies that have been carried out to derive DEMs and topographic maps from airborne laser altimetry data. 
NASA's laser scanning system covers a 130 to 200 m wide swath with a set of overlapping spirals. The densily distributd data, to- 
gether with an accuracy of 10 to 20 cm, lends itself into deriving accurate DEMs and into generating topographic maps that contain 
interesting morphological details necessary to analyze the surface characteristic as well as changes. The position of the system is 
determined by kinematic GPS. A ring-laser gyro inertial navigation system provides attitude information. Independent attitude in- 
formation is obtained from three widely separated GPS antennas on the airplane, suitable to control the INS drift. 
For the experiments described in this paper, five parallel flight strips have been bridged together to form a 4 km wide and 400 km 
long DEM. In order to check the accuracy, an independent DEM was derived by photogrammetric methods. A detailed analys con- 
firmed a strong agreement between the two DEMs. Also the topography depicted by the two approaches is very similar. 
1. INTRODUCTION Program the Airborne Topographic Mapper (ATM) - an air- 
borne scanning system - has been used on several missions in 
The vast ice sheets of Antarctica and Greenland cover almost Greenland and the Canadian Arctic. The program can be con- 
10% of the Earth's land surface. Together with sea ice they have sidered as a predecessor of a satellite laser altimetry program. 
a significant influence on local and global climate. Moreover, The Geoscience Laser Altimetry System (GLAS), currently 
the mass balance of polar ice masses is a sensitive indicator of under development, will be launched in the Earth Observation 
global climate changes. There is a growing concern that some System Land Ice Altimetry (EOS ALT-L) mission in 2002. 
ice fluctuation may occur at a rapid rate with an associated ef- 
fect on the global sea level. Thus it is imperative to monitor the The ATM laser scanning system covers a 130-200 m wide 
ice sheets on a global scale, assess their mass balance, and pre- swath with a set of overlapping spirals, providing a dense data 
dict their future behavior. set along the flight lines suitable for mapping ice sheet topogra- 
phy to unprecedented accuracy and detail. This continuous and 
This task can not be accomplished by using traditional, well- accurate mapping capability has major potential for mass bal- 
known and proven technologies. Ice sheets exhibit a dynamic ance studies. Although this high accuracy is achieved only 
behavior with some ice streams moving as much as 1 km per along the aircraft flight lines, the resulting elevation profiles can 
year. Their surface elevation changes throughout the year and also be used for mapping surface features, such as wind gener- 
the effect of global climate changes is superimposed on this ated ripples (sastrugi), lakes, and surface undulations. 
annual cycle. Clearly, detection of long term changes requires 
repeat measurements for several years. Another factor to con- This paper reports about the studies that have been carried out 
sider is the size - the area to be monitored is huge. Taking the to derive Digital Elevation Models (DEMs) and topographic 
required accuracy into account, the hostility of the area maps from airborne laser altimetry data. After a brief descrip- 
(remoteness, accessibility, weather), the picture of an enormous tion of the laser altimetry system the processing of raw data 
challenge emerges. including calibration aspects and error analysis follows. The 
last section deals with the derivation of a DEM in the Jakob- 
Laser altimetry provides a solution for precise mapping and shavns drainage basin from laser altimetry data and its compari- 
monitoring of polar regions. In NASA’s Arctic Ice Mapping son with a photogrammetrically derived DEM. 
42 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B1. Vienna 1996 
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