Full text: Proceedings International Workshop on Mobile Mapping Technology

7B-5-1 
OFF Method and Its Practice on Airborne GPS Data 
Processing for Photogrammetry 
Chen Xiaoming Liu Jiyu Li Deren 
Wuhan Technical University of Surveying and Mapping 
P. R. CHINA 
KEY WORDS: GPS, OTF, Ambiguity, Kalman Filter 
ABSTRACT 
1 his paper proposes a new 01F (Ambiguity Resolution On the Flv) method based on double difference 
Pseudorange/ carrier phase Kalman filter. With this method, the author has succeeded in processing the 
airborne GPS kinematic data of the Beijing GPS aided photogrammetry project. Results show that this 
method is capable of rapid and efficient resolving for carrier phase ambiguities for the case of long 
distance as 50 km and height difference of 2400 meters. After complete fixing ambiguity, differential 
positioning accuracy better than one decimeter can be obtained. In addition, this paper also executes 
three evaluations for the reliability of OTF solution 
1 INTRODUCTION 
Ambiguity resolution On The Fly (OTF) is a 
technique resolving integer ambiguity while the 
receiver is in moving. Using OTF technique, 
there is no need to perform static initialization, 
which is necessary in conventional precise 
kinematic positioning. Cycle slip, which is the 
most troublesome problem in precise kinematic 
positioning, is also easy to handle while using 
OTF technique In case of cycle slip, integer 
ambiguities can be resolved again on the fly. 
Therefore, the flexibility and reliability of 
kinematic positioning is improved. 
In last decade, GPS kinematic positioning 
technology has been used in photogrammetry 
successfully. 3D photostation coordinates can be 
determined at each exposure instant by 
differential kinematic positioning which use one 
airborne GPS receiver and one (or more) GPS 
receiver set up on ground reference station to 
receive GPS signals simultaneously. These data 
are introduced as additional observations into a 
combined block adjustment, resulting in densely 
controlled blocks with highly uniform accuracy 
distribution Introduction of these additional 
observations allows for a significant reduction 
for ground control required for photogrammetric 
blocks and increases the efficiency of 
photogrammetric mapping. 
If using conventional kinematic positioning 
technique in GPS photogrammetry, static 
initialization is necessary before aircraft take off 
This will not only extent observation time, but 
also prolong the aircraft waiting time. 
Additionally, a small swerve slope angle is 
needed to avoid cycle slip and lost of lock. This 
will cause a more fly distance and a longer time 
interval between tlightstrips than that of
	        
Waiting...

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