The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
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Length 
14m 
Flight speed 
30-50km/h 
Diameter 
Payload 
Cruise duration 
Anti-wind 
performance 
3.8m 
10kg 
2h 
4 grade 
Flight altitude 
Control radius 
Control style 
50-600m 
20km 
Auto/manual 
Table 2. Performance of the airship 
4.2 Flight Design and Test results 
Located in Liede Village, Tianhe District, Guangzhou, a so- 
called "city village”, the task region covers a total area of nealy 
1.0 square kilometers. 
The route design is in north-south direction, the length of each 
route being 1 km, the respective flight heights 300 m and 
240 m , the longitudinal overlap 80% and lateral overlap 60% 
with horizontal placement of the camera. The 300m flight 
height parameters are as follows: 
1. Image ground resolution is 0.1 m; 
2. Ground coverage is :436.8*291.2m; 
3. Exposure interval in flight direction:58.2m, designed 
as 60m; 
4. Route interval is 174m, designed as 150m; 
5. 
The flight was carried out on October 10, 2007, with a 10- 
person team, of which two are manipulators, one in ground 
station, three ground crew, two for logistics support, and two 
for data processing. 
We arrived at the field at 8:00am on the 10 th of October, 2007. 
The air inflation started at 9:00a.m.. The unmanned airship took 
off at 12:20p.m., and landed at 12:50p.m.. We left the airfield at 
13:30p.m. 
(a) Panorama of the unmanned airship (b) Route Planning 
Figure 5. Panorama of the unmanned airship and route 
planning 
Figure 6. Orthoimage of Liede Village, Tianhe District 
5. THREE UNMANNED AERIAL 
PHOTOGRAMMETRY AIRCRAFT COMPARISON 
Based on the aerial photographic tests of the above-mentioned 
unmanned helicopter, unmanned fixed-wing aircraft and 
unmanned airship, the following review is made on the three 
low-altitude aerial photographic system as regard to their flight 
security, photographic quality and operation efficiency. 
5.1 Security Comparison 
Security performances include two aspects: security of the 
system itself and safety of ground persons as well as properties. 
Especially in the case of a forced landing, the ground persons 
should have sufficient time to avoid collision. 
According to the analysis of failure probability, mechanical 
power equipment of unmanned helicopters is most complex, 
while that of airships and fixed-wing aircrafts are almost 
equivalent, being much simpler compared with helicopters. 
Therefore, unmanned helicopters have the highest failure 
probability. 
Considering the safety of ground persons, the spherical airship 
is made by strong composite film or senior PVC material, and 
the ball is filled with helium. Even when the airship has 
loopholes, it will still descend slowly. If an unmanned fixed- 
winged aircraft can open the parachute in time, slow descending 
can also be realized. With a main rotor, the parachute rescue 
equipment can’t be installed at the top of the unmanned 
helicopter so that it can not achieve slow descending. Though 
equipped with self-rescue devices(NRI ,2005) and a parachute 
will pop up from the rear of the helicopter in an emergency, the 
high speed rotating main rotor will still pose a threat to the 
unpredictable losses of ground persons and properties. 
Comparing the three equipments, unmanned airship has got the 
highest safety performance, while unmanned helicopter is least 
secure. 
5.2 Quality Comparison 
One main quality investigation is to inspect if an aircraft can 
realize cross-point flight according to the professional 
photogrammetry requirements. Based on the existing flight test 
analysis, the aerial photographic system of unmanned 
helicopters, unmanned fixed-wing aircrafts and unmanned 
airships can all meet the photogrammetry flight requirements. 
In contrast, the unmanned helicopter has the highest point 
accuracy, as seen in the 1 m photographic flying height changes 
of the 384 Zhumadian images. The accuracy of unmanned 
fixed-wing aircraft is in the second place, with the route height 
changes of less than 3 m in the 840 images of Guangzhou New 
Passenger Station. 
5.3 Efficiency Comparison 
If the payload is definite, there are two primary factors that 
affect the working performance, i.e., location adaptability and 
cruise duration. 
As far as location adaptability is concerned, unmanned 
helicopter does not need special take-off and landing sites and 
runways. Being capable of vertical take-off and landing, it 
doesn’t need special take-off and landing site in operation. With