The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008
1227
suspended take-off and landing and without the need of a
runway, unmanned airship would be the second choice, but a
field of no shorter than three fuselage lengths is needed. A
stadium within the city, a square or even a lawn can all serve as
the landing fields, yet it hardly needs a landing field when
flying outside the city.
For unmanned fixed-wing aircrafts, there are restrictions on the
airfield, the runway of which should be even and flat, have at
least ten fuselage lengths and two wingspan widths. In addition,
adequate headroom is also required. According to Guangzhou
flight test, such technologies as catapult take-off, hit net
recovery, water surface take-off and landing or a combination
of both must be developed for an unmanned fixed-wing aircraft
to better suit the flight in well-developed water networks and
vegetation-intensive areas, which ensure that the unmanned
fixed-wing aircraft can take off anywhere and at anytime.
Under the conditions of no pixel compensation device, the
maximum flying speed of a low-altitude unmanned aircraft will
be restricted. Take the test in Zhumadian city for example, the
provisions of pixel displacement is 8 = 1/3 pixel, i.e., viz. .
Meanwhile, the exposure time is set at t = ^ ^ ^Os , relative
altitude at ^ = 236m , an( j altitude difference at ^ = ,
focus at /-12mm , w hj c h the maximum permitted speed
can be calculated at w ~ 84km / h Therefore, it is particularly
important to improve the range capability of an aircraft in
speed- limited circumstances. The cruise duration of an
unmanned helicopter, an unmanned fixed-wing and an
unmanned airship used in the tests reported this paper is 2.5 h,
2h and 2h respectively, all of which needs further improvement.
6. CONCLUSION
Through comprehensive analysis and summary of the
experiment on aerial photogrammetry of unmanned helicopters,
unmanned fixed-wing aircraft and unmanned airship, following
conclusions can be drawn:
1. In regard to professional photogrammetry, all three systems
of unmanned aircraft low-altitude aerial photogrammetry meet
the requirements of small regional large-scale aerial
photogrammetry.
2. Taking security, cost, efficiency into account, development
of unmanned fixed-wing aircraft and unmanned airship should
be given priority. Perfecting unmanned airship technology,
solving the problem of flying in urban areas and improving the
unmanned fixed-wing technology all help to realize highly
efficient and secure flight in areas outside the city.
3. The development of low-altitude photogrammetry system of
unmanned civil aircraft should be combined with professional
application, matching the system's performance with
professional requirements so as to avoid the waste of resources
caused by the simplified civil use of high-performance military
aircraft.
Following proposals are made to further improve the
technology in low-altitude unmanned aircraft aerial
photographic system:
1. Three-axis stabilized platform technology, the key problem
in low-altitude unmanned aircraft aerial photogrammetry
system, needs further improvement.
2. The study of double-engine and double-generator unmanned
fixed-wing aircraft helps to further improve the reliability and
range capability of unmanned fixed-wing aircraft.
3. Payload swath is not only closely related with altimetric
measurement accuracy, but is also an efficient way to improve
the operating performance. At present, in the circumstances of
limited single pixel CCD, the study of optical synthetic aperture
camera is necessary.
REFERENCES
[1] LIU Xianlin, 2006. Survey and Mapping College Academic
report
[2] LIU Changhua, WANG Chenglong, LIU Xianlin, 2007.
Analysis and application of a close-to-earth digital aerial
photogrammetry system with over-light plane, Journal of
Wuhan University (Natural Science ), 26(5), pp.523-528
[3] Tiwana Walton, 2007. Unmanned Aerial Vehicle Mission
Planning to Kangerlussuaq,Greenland.http://nia.ecsu.edu/ur/
0708/07summerintems/tiwanawalton-technical-report-summer
2007.pdf. (accessed 25 April. 2008)
[4] schiebel,2008. http://www.schiebel.net/ (accessed 25 April.
2008)
[5] NRI ,2005, AutoCopter™ - Autonomous Unmanned
Helicopter, http://www.airwarbirds.com/pdf/NRI-Multi-Produc
t-Fact-Sheet-11.21.05.pdf. (accessed 25 April. 2008)
[6] WU Yundong, ZHANG Qiang, WANG Hui et al, 2007.
The Technique of Low Aerial Photography and
Photogrammetry System by Unmanned Helicopter. Surveying
Science and Technology Journal, 24(5), pp. 328-331
[7] CHEN Hongbin, MA Shuqing, WANG Gai, et al, 2001.
Aerial remote sensing system based on micro-aircraft automatic
driving aircraft. Remote sensing technology and application,
16(3): pp. 144-148
[8] SUN Jie, LIN Zongjian, CUI Hongxia, et al, 2003.
Unmanned aircraft and space remote sensing monitoring system.
Remote Sensing Information, (1), pp. 49-51
[9] YAN Lei, LU Shuqiang ZHAO Hongying, et al, 2004. Key
technologies research of UAV aviation remote sensing systems.
Journal of Wuhan University (Engineering Science). 37 (6), pp.
67-70