analytical plotter (Ge, 1993). A two-dimensional
calibration method considering opto-electric errors has
been proposed (Tao et al., 1993), together with a robust
method of scale factor measurement for CCD camera
system calibration (Tao et al., 1995). The design work
has been completed for a multi-spectrum remote
sensing image forming system by using an enhanced
video technology to work within the visible light band and
near infrared band, which is able to provide more multi-
spectrum image information for agricultural production
(Zhou et al., 1994).
Between 1992 and 1996, NBSM has completed the
aerial photographic work for an area of 2,530,000 square
kilometres of the country, finished the updating work of
1:50,000 scale topographic maps of the economy edition
and the 1:10,000 topographic maps, and made 230,000
sheets of topographic maps of various scales.
2. 2 Aerial Triangulation
In the past few years, China has been working actively to
carry out experiments in GPS-supported bundle block
adjustment, so as to greatly decrease the number of the
field control points and shorten the mapping cycle.
Success has been achieved in the development of
kinematic phase differential. GPS software DDKIN to
survey the spatial real time coordinates of photographic
stations, and a software for combined adjustment
WUuCAPS for GPS-supported triangulation, which can
fulfil the precision requirements for topographic mapping
at scales between 1:1,000 and 1:100,000 (Li and Yuan,
1995). Methods have. been proposed for the
determination of the decentration between the airborne
GPS antenna and the camera (Zhu et al., 1995), and
exploration has been made for two methods for the
determination of the interior orientation elements by
using kinematic GPS data (Yuan and Li, 1995).
In 1996, the GPS-supported aerial triangulation was
used in the aerial photography in Hainan Island and for
the production of 1:10,000 DEM and orthophoto
database. This project is part of a program with
Australian supporting funds.
In addition, by using simulation data, work has been
done for calculating the influence of space-borne GPS
positioning accuracy on the estimation of ground point
coordinates under the CCD Pushroom Scanning mode
(Li and Wang, 1994a).
2. 3 Digital Photogrammetry
In the past four years, analytical plotter has still been the
main instrument used in photogrammetric production in
China. Each year about fifty pieces of China-made JX-3
or APS-2 analytical plotters are sold on the domestic
market, and a few are exported to countries like Pakistan.
Analogue instruments like B8S and Topocart B have
been: transformed into computer-controlled
photogrammetric systems.
In the meantime, China has imported 117 total stations,
44 graphics work stations and 1369 PCs for the
establishment of seven pilot bases for digital surveying
and mapping production in Sichuan, Shanxi,
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996
Heilongjiang, Beijing, Shanghai, Guangdong and Hubei,
which are providing necessary conditions for the
application of digital photogrammetry in practical
production in the country.
After fifteen years of research and development, Wuhan
Technical University of Surveying and Mapping has
produced WuDAMS--a software package for fully digital
automatic mapping, which is known on the international
market as VirtuoZo, a joint product with an Australian
company taking quite a bit of share of the market
internationally. With this system, a series of automated
functions can be realized, such as automatic interior and
relative orientation, automatic point transfer for
aerotriangulation, automatic image matching for DEM
generation and digital orthophoto production (Zhang et
al., 1994a). Coupled with this development, research has
also been done for high precision location operator for
straight line and corner point on digital images (Zhang et
al., 1994b), relaxation based edge extraction (Qiu and
Zhang, 1994) and multi-point least squares matching
with array relaxation under variable weights (Zhang and
Wu, 1994). :
For non-semantic information extraction in digital
photogrammetry, the researchs include an automatic
quality diagnosis method for digital image matching
based on orthophoto and stereo orthophoto pair (Li et al.,
1994b), a least squares matching method with dynamic
parameter selection for SPOT image data (Tao, 1993), a
global image matching method based on dynamic
programming (Qiu, 1994) and a feature based matching
using dynamic programming (Zheng, 1992).
For semantic information extraction in digital
photogrammetry, a lot of active research and studying
have been done in the last four years. The main
research results are :
An image segmentation method based on Hough
transformation (Zhang and Min, 1992), and a snake
approach for aerial image segmentation based on active
contour model (Liu and Lin, 1995) is proposed. The
application of morphological transformation in edge
feature extraction are investigated. Some structure
elements can be used for edge detection without the
influence of bar noises (Zheng and Zhou, 1992). After
that the pattern recognition of two-dimensional objects
can be done by using dynamic programming (Zheng and
Li, 1994). In man-made object recognition, a wavelet
method is used for image edge election (Li and
Shao,1994a) and a house extraction algorithm with
multiresolution wavelet analysis and information fusion
has been suggested (Li and Shao, 1994b). Another
automated method to extract buildings from the aerial
images in consideration of the noise of the surroundings
has also been proposed (Tao. and Lin, 1994a).
In order to overcome the present difficulties in realizing
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