The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
need for UAS has outweighed the lack of reliability. Therefore, 
generally speaking, UAS technology requires improvements to 
be made to its reliability. Obvious issues are the vulnerability 
of GPS-based navigation technology, the need for reliable data 
links and the predominant use of a single engine. The use of 
GPS as the sole means of navigation is, certainly, an issue. 
However, wide area augmentation services of GPS and of the 
coming Galileo system, the Safety of Life (SoL) service of 
Galileo, and their hybridization with redundant IMU 
configurations, barometric altimeters and magnetometers will 
provide a sufficient degree of navigational integrity (section 
4.1). Reliable data links, particularly for long range UAS, can 
be based on satellite communications. Single engine 
configurations can be replaced by double engine ones —or 
equivalent redundant configurations— such that the UA be 
able to fly on one of the two engines. It goes without saying 
that higher reliability can easily translate into more weight and 
power consumption. 
Integration in the civilian airspace. Currently there are many 
initiatives, projects, professional associations and government 
agencies dealing with the integration of UAs in the regulated 
civilian airspace. At the international level, the International 
Civil Aviation Organization (ICAO) has created the Unmanned 
Aircraft Systems Study Group (UASSG) with, among others, 
the purpose of developing a regulatory concept for UASs. The 
North Atlantic Treaty Organization (NATO) has been active in 
the topic for years, mainly in the operation of military UASs in 
the non segregated air space. It has or is about to produce 
standards on standard interfaces, on airworthiness requirements, 
on Aerial Traffic Management (ATM) and others. In Europe, 
the European Commission’s (EC) regulatory agency, the 
European Aviation Safety Agency (EASA) and the European 
Organisation for the Safety of Air Navigation 
(EUROCONTROL) have to be mentioned. EASA is currently 
working on the UAS certification policy and 
EUROCONTROL does it on the integration of both military 
and civilian UASs in the non-segregated airspace. Also in 
Europe, the Working Group 73 “Unmanned Aircraft Systems” 
of the European Association for Civil Aviation Equipment 
(EUROCAE) elaborates materials to support that unmanned 
aircraft can operate safely within non-segregated airspace in a 
manner compatible with other airspace users. In the US, the 
Federal Aviation Administration (FAA), in addition to several 
regulations has created the Unmanned Aircraft Program Office 
(UAPO) whose goal is to regulate the operation of UASs in the 
non-segregated airspace no later than 2011. (The Department 
of Defense (DoD) and the National Aeronautics and Space 
Administration (NASA) are active in this field since many 
years.) Also in the US, Committee F38 of ASTM International, 
one of the largest voluntary standards development 
organization, has produced UAS standards, ranging from 
airworthiness, to terminology, to sense-and-avoid 
specifications. Last not least, the Japan UAV Association 
(JUAV) has established standards for the commercial use of 
UASs in non populated areas since 2004. 
Common treats in the above mentioned initiatives are that an 
UAS shall satisfy national and/or international airworthiness 
criteria; that it shall be able to respond to ground-to-air and air- 
to-air voice communications; that it shall support a sense-and- 
avoid capability with respect to other aircraft, equivalent to that 
of a piloted plane and that it some procedures and maneuvers 
shall be automated. 
Social acceptance and safety reputation. Damage caused by a 
flying vehicle depends on a number of factors like its kinetic 
energy (related to weight and speed) and its engine 
(combustion or electric). UA crashes are far less damaging than 
their manned counterparts but may be more frequent. Repeated 
successful flights over populated areas will pave the way for 
social acceptance of UAS operations while a few accidents will 
do a long lasting reputational damage. In the last years there 
have been successful experiences like the July 2004 historic 
flight over Amsterdam but also tragic accidents like the 
October 2006 Kinshasa crash where two people were killed 
and two other suffered from bums. The degree of social 
acceptance of UAS will ultimately depend on the popular 
combined perception of safeness and usefulness of UAS 
operations. And to this point, it is probably more than cost 
effective mapping that may count; support to search and rescue 
operations of people lost in the wilderness or adrift at sea are 
the kind of applications likely to generate the required empathy. 
5.2 The immediate future 
The discussed challenges notwithstanding, there are market 
niches that are an opportunity for actual business and further 
technology development and testing. Today, there are 
situations where the odds of losing a pilot are simply too great. 
Filming a volcanic eruption from close quarters, is an example 
of something that the market is willing to pay for and that we 
were not able to do before the UAS technology. However, 
beyond the one-of-a-kind applications, it is the general ones 
(section 1) that have the potential to develop future big markets. 
In the next few years the most iikely scenario is that of three 
parallel tasks; surviving on special projects, further developing 
the technology and fighting the battle of integration in the 
regulated airspace. 
6. CONCLUSIONS AND OUTLOOK 
Like other professional communities, the PRS one has started 
to use the UAS technology and has recognized its big potential. 
In this paper we have discussed the technical and regulatory 
issues related to UAS-based high-resolution and high-quality 
PRS. On the technical side, a number of challenges have been 
identified and the solutions adopted by the authors at the IG 
have been outlined. Beyond the challenges, some advantages of 
the UAS technology for PRS have been explored. 
The main challenge, though, for UAS-based PRS to become a 
mainstream technology is the clarification and the development 
of the regulatory issues; particularly, of the integration of UAs 
in the non-segregated civilian airspace. Indeed, this is not an 
easy task. However, the international UAS marketplace is 
growing fast and the aviation authorities and regulatory bodies 
are aware of this. Not so many years ago, the 
commercialization of medium- and high-resolution satellite 
images extended the paradigm of image acquisition. And the 
paradigm may continue to evolve... 
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