The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
standard map products. The geoid undulation model used to 
transform the data to orthometric height can become a dominant 
error source in many areas where there is little or no gravity 
data. Thus an accurate geoid is required for a sea level 
referenced DEM. 
For this purpose, Intermap has developed a new airborne 
inertial gravity system (AIGS) and airborne geoid mapping 
system (STARGRAV), as described in the above section. It is 
based on the navigation components of STAR system: 
differential GPS (DGPS), the strapdown inertial navigational 
system (INS), and the STAR acquisition system. Using the new 
technique, the orthometric height can be determined to the 
accuracy of the ellipsoidal height measurements provided by 
Intermap IFSAR system. As a sub-system to the entire IFSAR 
data process the AIGS and STARGRAV are integrated into the 
STAR system and also can be implemented separately for 
airborne gravimetry applications. 
Combining two technologies: IFSAR technology and airborne 
gravimetry technology, the Intermap STAR system can provide 
all required mapping information (thematic, topographic and 
geoid undulations) with high accuracy in a single pass. This 
provides an efficient way to determine orthometric heights 
without ground gravity and geoid data. Figure 11 shows the 
concept of the integrated airborne IFSAR mapping system. As 
shown in Figure 11, other benefit of the integrated mapping 
system is that the interferometric DTE can be used for the 
terrain correction of geoid determination when no terrain model 
is available for the areas of interest. 
Figure 11: Diagram of integrated airborne IFSAR mapping 
system 
4. CONCLUSIONS 
In this article, an integrated airborne IFSAR mapping system is 
introduced. The major advantage of the integrated IFSAR 
mapping system is that all required mapping information 
(thematic, topographic information and geoid undulation) can 
be obtained in a single pass by one mapping system. It provides 
a great potential for mapping in mountainous or tropical regions 
where accurate topographic and gravimetric information is not 
available and/or the traditional mapping techniques can not 
provide such information. 
STAR based technology has proven to be a robust, fast, 
accurate and cost-effective technology for large area 3-D 
mapping. Based on the navigation components of STAR system, 
Intermap has developed airborne gravity and geoid mapping 
system for precise airborne gravity and geoid determination. 
Many experiments have demonstrated that the accuracy of the 
airborne gravity anomaly from STAR AIGS is 1-3 mGal (la) 
when using a 120 second filtering. Extremely robust results are 
obtained, even during aircraft turns and turbulence events. The 
airborne gravity-derived geoid can be directly used as a precise 
vertical reference for orthometric heights. The resulting 
accuracy of the geoid model determined using the airborne 
gravity measurements is 5~ 10 cm (la) when compared with an 
independent geoid reference. 
The integrated STAR mapping system provides a new 
generation of determining geoid referenced digital elevation 
models and ortho-rectified images without external ground 
measurements. 
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ACKNOWLEDGEMENTS 
The authors would like to acknowledge their many colleagues 
at Intermap for sharing information and results.