Roman Arbiol 
  
MAP PRODUCTION IN VENEZUELA USING AIRBORNE INSAR 
Roman ARBIOL*, Gloria GONZÄLEZ** 
*Institut Cartografic de Catalunya, Spain 
arbiol@icc.es 
**Servicio Autonomo de Geografia y Cartografia Nacional de Venezuela, Venezuela 
gloriag@telcet.net.ve 
KEY WORDS: Interferometry, Airborne SAR, Rain Forest Cartography, Radar images, DEM 
ABSTRACT 
This paper is a final report of a project to map a cloudy tropical region of 266,616 km” in southern Venezuela using 
single pass airborne interferometric synthetic aperture radar (InSAR). The paper summarizes the main activities 
involved, the practical experiences and the final conclusions. It does not attempt to describe the radar processing in 
depth: only the detail needed to make it understandable is given. The report demonstrates that airborne radar 
interferometry is an operational tool for mapping projects in cloudy areas. 
1 INTRODUCTION 
The Servicio Autónomo de Geografia y Cartografia Nacional de Venezuela (the National Mapping Agency of 
Venezuela) has undertaken the mapping of the vast region between the Orinoco River and the Brazilian border. This 
remote region of Venezuela has a warm and humid climate, with almost permanent cloud cover. The topography is hilly, 
with few flat areas and very abrupt elevations emerging from the plain. The land is mostly covered by rainforest, with 
trees reaching 40 meters in height. The project consisted in producing 5 meter pixel digital orthoimages and orthoimage 
maps at 1:50,000 scale, with 40 meter contours derived from a digital elevation model over a region of 266,616 km’. 
The total number of map sheets covering the area is 536. 
The Institut Cartografic de Catalunya (Cartographic Institute of Catalonia) submitted a technical proposal based on 
interferometric SAR technology to ensure that products would be obtained and delivered in a predictable period of time, 
regardless of the weather conditions and abundant cloud cover. The accuracy and pixel size specifications excluded the 
use of satellite radar, and therefore the AeS-1 single pass airborne interferometric radar from AeroSensing 
Radarsysteme, GmbH (Wessling, Germany) was proposed and selected for the project. 
After a preliminary ground survey campaign and the preparation of the logistics, the flight mission begun on October 20, 
1998 and it ended successfully on February 5, 1999. During the whole year 1999 the radar data set has been processed 
and all the maps have been produced. 
2 THE AES-1 RADAR 
The AeS-1 interferometric SAR of AeroSensing Radarsysteme (Moreira, 1996) is an advanced radar operating in the X- 
band that is capable of delivering radar images with pixel sizes ranging from 0.5 to 5.0 m. and elevation data with 
nominal accuracy of 5 to 50 cm. The radar emits and receives the signals using two antennas that are rigidly mounted on 
one side of the airplane and 0.59 meters apart, so as to form the baseline of the interferometric geometry. The radar 
illuminates the terrain laterally at an angle ranging from 20° (near range) to 67° (far range). Due to the separation of the 
antennas, the range to a point is slightly different as measured by each antenna; this range difference corresponds to a 
phase difference from which the elevation is determined. 
The motion of the airplane affects the phase of a point, so this motion has to be recorded and compensated. The current 
configuration uses GPS and INS data from an Applanix system to determine the effects induced by the motion of the 
aircraft and to obtain the orientation of the sensor. In addition, the aircraft had to follow the flight lines with almost no 
deviations (less than 20 m). Therefore, the flight navigation system makes use of DGPS data transmitted from a 
reference station. The transmitter’s maximum range is 300 km and its location was carefully chosen so as to always have 
  
24 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B1. Amsterdam 2000. 
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