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ogrammetric 
ON THE USE OF MODERN GPS RECEIVER AND SOFTWARE TECHNOLOGY FOR PHOTOGRAMMETRIC 
APPLICATIONS 
Holger Schade 
Product Manager 
Leica AG 
AVS 
CH-9435 Heerbrugg 
Switzerland 
Commission Ill, Working Group 1 
KEY WORDS: GPS, Navigation, Integration 
ABSTRACT: 
In the last years, photogrammetric equipment in an aircraft can not be restricted to an aerial camera alone. The use of 
the Global Positioning System (GPS) for photo flight navigation and automatic control of aerial cameras is already 
widely spread. Also, the concept of GPS based aerial triangulation by using post processed GPS raw data in 
combination with photogrammetric image data can be considered as operational. The cost benefits for the user, by the 
reduction of flying time and ground control have lead to a fast acceptance of this new technology. It is the aim of this 
paper to give an overview of the performance of ,state of the art‘ GPS hard- and software and to discuss requirements 
and solutions posed by photogrammetric applications. Two points which have caused uncertainty amongst 
photogrammetrists will be specifically addressed: the performance of new GPS receivers and the question if dual 
frequency receivers are needed in photogrammetric applications. 
KURZFASSUNG: 
In den letzten Jahren wurde zunehmend deutlich, daß man die photogrammetrische Ausrüstung in einem Flugzeug 
nicht allein auf die Luftbildkamera beschränken kann. Mittlerweile, wird GPS für die Flugnavigation und das 
automatische Auslösen der Kamera an vordefinierten Positionen bereits häufig in der Praxis eingesetzt. Auch die GPS 
gestützte Aerotriangulation kann heute als operationell betrachtet werden. Die Kostenreduktion durch die kürzeren 
Flugzeiten und die deutliche Reduzierung der erforderlichen Paßpunkte haben zu einer schnellen Akzeptanz dieses 
Verfahrens geführt. Es ist das Ziel dieses Aufsatzes die Qualität und Leistung der aktuellen Hard- und Software 
aufzuzeigen und darüber hinaus die Anforderungen und Lösungsansätze für photogrammetrische Anwendungen 
aufzuzeigen. Speziell werden zwei Punkte vertieft diskutiert, die in der nahen Vergangenheit einige Unsicherheiten bei 
Photogrammetrie Anwendern hervorgerufen haben: die Güte der neuen Empfängergenerationen und die Frage ob 
Zweifrequenzempfänger in photogrammetrischen Anwendungen notwendig sind. 
1. INTRODUCTION 
GPS for photogrammetric applications has become 
extremely popular in the last decade, due to the 
advantages of accuracy, speed, versatility and economy. 
Generally, there are three major areas where GPS plays 
a key role in photogrammetry: 
* high precision photo flight navigation for a 
reduction of flying time 
* automatic camera release at predefined 
positions, for a perfect image overlap and less 
camera operator stress 
* combined block adjustment of GPS and image 
data, for a significant reduction of ground 
control points 
Flight navigation and automatic camera release is 
already standard for technologically advanced aerial 
camera users. Also, the financial benefits of the 
combined block adjustment (CBA) has been accepted 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
widely. Products, such as the LEICA ASCOT system 
(Merminond [1994]), already provide a continuous and 
comfortable data flow from the flight planning to the 
block adjustment. However, the rapid changes in GPS 
receiver technology and processing algorithms, require a 
constant evaluation of the currently available methods 
and products. It is the aim of this paper to give an 
overview on the current GPS technology (hard- and 
software) and to discuss the impact of this new 
technology on the specific photogrammetric applications. 
2. ACCURACY REQUIREMENTS 
The required accuracy for the photogrammetric GPS 
application can be grouped in two main areas: 
navigation + automatic camera release and as a second 
area GPS post processing for combined block