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Mapping without the sun
Zhang, Jixian

Xinxin Zhu a ’, Guo Zhang b , Qing Zhu c , Xinming Tang d
a State key laboratory of Information Engineering in Surveying ,Mapping and Remote Sensing, Wuhan University,
Wuhan, China, 430079, xxzhu20@163.com
b State key laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University,
Wuhan, China, 430079, guozhang@whu.edu.cn
c State key laboratory of Information Engineering in Surveying ,Mapping and Remote Sensing, Wuhan University,
Wuhan, China, 430079, zhuqing@lmars.whu.edu.cn
d Key Laboratory of Geo-informatics of State Bureau of Surveying and Mapping, Chinese Academy of Surveying and Mapping,
16Beitaiping Road,Beijing, China, 100039, tang@casm.ac.cn
KEY WORDS: geometric test range, calibration, free cloud, flat area, vertical displacement
The high resolution satellite such as IKONOS, SPOT5 have built many geometric test ranges around the world for in-flight
calibration to obtain high horizontal and vertical accuracy. This is one reason that their products are widely used in many fields.
For a satellite geometric test range, how to select one is a critical problem. This paper focuses on the weather and terrain conditions
while choosing a satellite geometric test range in China.
In this paper, the weather condition is analyzed first. A free cloud area is likely to be chosen, and several areas will meet the
condition. Then do terrain analysis for those areas which content weather condition, and select flat area because it can calibrate
satellite parameters as well as mountain area and flat area is more convenient for arranging GCP (Ground Control Point). Area and
cost conditions haven’t been detailed because authors take them as subjective factors. Last, an experiment is performed to show the
process of test range selection. This experiment may give some suggestions about how to select a test range.
With the development of remote sensing technology, satellite
images are widely used in many areas. Some satellite images
not only have high spatial resolution, but also have high
location accuracy, such as IKONOS, SPOT5, and ects. As we
know, during the emission of satellite, several factors causing
the geometric parameters value which have been validated on
the ground varied, launch shock; zero gravity. (D. Mulawa,
2004) For the purpose of high location accuracy, ground
calibration is needed to obtain a priori value for on-orbit use.
Geometric test ranges are designed for this aim. SPOT series
satellites, IKONOS, ALOS and so forth all have many test
ranges around the world. By using geometric test ranges for
calibrating, location accuracy can be improved prominently.
During the first year of SPOT5’s running, its location accuracy
being improved from 600 m rms to 20 m rms by means of
ground geometric test ranges.(Bouillon and Gigord, 2004)
(Bouillon et al., 2003) (Gachet, 2004) (Breton, E, 2002) This
affirms geometric test ranges is a good method for geometric
Satellite geometric calibration is one aspect hindering the avail
of satellite image. And because no such test ranges has been in
China now, in order to make good use of satellite images, it is
essential to know how to select a test range first.
To select a satellite test range generally consider four aspects as
• weather condition
• terrain condition
• area condition
• cost condition
Weather condition and terrain condition are mainly to be
considered. Since area condition is depend on the satellite’s
swath width, and cost condition sometime is a subjective factor.
So in this article the emphasis is analyzing the weather and
terrain conditions.
2.1 Weather condition
Cloud is being analyzed in weather condition. Its influence is
on image quality. As satellite remote sensing is different from
aerial remote sensing which can choose when to fly on the test
range, satellites are running like clockwork in the space. The
time pass by the test ranges can not be changed after emission.
On purpose to obtain operative images when imaging on the
test ranges, free cloud weather is needed. So a place having
high probability of free cloud is like to be chosen (Gene Dial,
2.2 Terrain condition
In spatial remote sensing calibration, a site having superior
height variance is accepted for test range to eliminate the
influence caused by height to improve horizontal accuracy. But
space remote sensing is different. As the orbits of satellite are
far away from the ground, satellite imaging is similar to parallel
projection. The influence for horizontal accuracy due to great
hypsography does not appear evidently, and for vertical
accuracy, a good DEM can be used to improve it.