2-4-7 
Statistic 
Easting [m] 
Northing [m] 
Height [m] 
Mean 
0.015 
0.014 
0.044 
Median 
0.013 
0.011 
0.045 
Maximum 
0.050 
0.034 
0.130 
RMS 
0.020 
0.018 
0.052 
Table 3. Ground coordinate difference for 15 control 
points measured on stereo pairs from different 
passes. 
The ultimate accuracy test for the direct orientation 
derived from GPS/INS after the boresight was applied, 
is the comparison of the ground coordinates obtained by 
the photogrammetric methods based on the directly 
oriented imagery, and the ground coordinates of the 
GPS-determined control points. The control points used 
in this test were determined with accuracy of ~1.5 cm 
per coordinate. They were located 18 m from the 
perspective center of the camera, when the directly 
oriented imagery was collected. The comparison 
performed on 4 control points is presented in Table 4. 
Point 
Easting [m] 
Northing [m] 
Height [m] 
1 
0.002 
0.029 
0.008 
2 
0.009 
0.015 
0.000 
3 
-0.019 
0.029 
0.010 
4 
-0.059 
0.018 
0.009 
Table 4. Coordinate difference between control points 
measured on the imagery and the ground truth. 
5. SUMMARY 
Several practical aspects of the direct platform 
orientation in airborne and land-based applications were 
discussed. The integrated system based on medium to 
high quality strapdown INS and dual frequency 
differential GPS offers a capability for automatic and 
direct imaging sensor orientation with high accuracy. 
The crucial factors limiting the direct orientation quality 
are the multisensor system calibration and rigidity of the 
common mount. Boresight and lever arm are the two 
most important calibration components that have to be 
preformed with great caution. GPS/INS, although very 
attractive and commercially available at a competitive 
price cannot always replace the aerotriangulation - for 
example areas of high-level radio interference cannot be 
surveyed with high accuracy by GPS/INS systems due 
to the excessive losses of GPS lock. Furthermore, the 
high-accuracy aerotriangulation has to be performed for 
the boresight calibration and direct orientation quality 
control when working with optical or frame digital 
sensors. 
REFERENCES 
Abdullah, Q., (1997): Evaluation of GPS-Inertial Navigation 
System for Airborne Photogrammetry, presented at 1997 
ACSM/ASPRS Annual Convention and Exposition, April 
7-10, Seattle, WA. 
Da, R. (1997): Analysis and Test Results of AIMS GPS/INS 
System, Proc. ION GPS, pp. 771-780. 
Divis A. (1999): WAAS: Beleaguered, Bolstered, GPS World, 
March 1999, pp. 12-17. 
Grejner-Brzezinska, D. A. (1997): Airborne Integrated 
Mapping System: Positioning Component, Proc. 53rd 
ION Annual Meeting, Albuquerque, NM, pp. 225-235. 
Grejner-Brzezinska, D. A. (1998): Direct Platform 
Orientation with Tightly Integrated GPS/INS in Airborne 
Applications, Proceedings of ION GPS, Nashville TN, 
September 16-18. 
Grejner-Brzezinska D. A., Da, R., Toth C., (1998): GPS Error 
Modeling and OTF Ambiguity Resolution for High- 
Accuracy GPS/INS Integrated System, Journal of 
Geodesy, 72(11), pp. 628-638 
Grejner-Brzezinska, D. A. and Wang, J. (1998): Gravity 
Modeling for High-Accuracy GPS/INS Integration, 
Navigation, Vol. 45, No. 3, pp.209-220. 
Kerr III, T. (1994): Use of GPS/INS in the Design of 
Airborne Multisensor Data Collection Mission (for 
Tuning NN-based ATR Algorithms), Proc. ION GPS, Salt 
Lake City, Utah, pp. 1173-1188. 
Krafcik J. and Guevara A. (1999): GPS for Air and Space 
Power, No. 133, January 18, 1999. 
Lithopoulos, E., Reid, B., Scherzinger, B., 1996. The Position 
and Orientation System (POS) for Survey Applications, 
International Archives of Photogrammetry and Remote 
Sensing, ISPRS Comm. Ill, Vol. XXXI, part B3, pp. 467- 
471. 
Skaloud, J., Cramer, M., Schwarz, K.P., (1996): Exterior 
Orientation by Direct Measurement of Camera Position 
and Attitude, International Archives of Photogrammetry 
and Remote Sensing, Vol. XXXI, Part B3, pp. 125-130. 
Schwarz, K. P. (1995): INS/GPS as a Georeferencing Tool for 
Multi-Sensor Systems, presented at the Mobile Mapping 
Symposium, May 24-26, Columbus, OH. 
Schwarz, K. P., Wei, M. (1994): Aided Versus Embeded A 
Comparison of Two Approaches to GPS/INS Integration, 
Proc. IEEE Position Location and Navigation 
Symposium, April 11-15, Las Vegas, NE, pp. 314-321. 
Toth, C. (1997): Direct Sensor Platform Orientation: Airborne 
Integrated Mapping System (AIMS), ISPRS Comm. Ill, 
Vol. XXXII, part 3-2W3, pp. 148-155. 
Toth C., Grejner-Brzezinska, D. A. (1998): Performance 
Analysis of the Airborne Integrated Mapping System 
(AIMS™), ISPRS Commission II Symposium on Data 
Integration: Systems and Techniques, July 13-17, 
Cambridge, England, pp.320-326.