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