International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004
Figure 8. Change detection for image-map
For landuse data with topology in vector format, it can be done
just as color landuse map, only after it is colored for each
landuse type.
Change information will be extracted by threshold value or
other methods, but it is often mixed with noise and needs
interpretation by human-computer interactive. Finally they are
digitized into vector data and endued with corresponding
attribute, such as record number, area, coordinate and so on.
Softwares as ARC/INFO, ARCView, ERDAS or MAPGIS can
be good choices.
3.4 Investigation in the field
Investigation in the field is an important means to assure the
quality of results.
3.4.1 Aim: (1) verify change information: check each change
parcel if truly or false, acquire its true area, range and landuse
type; (2) complete missing change; (3) measure DOM precision;
(4) correct administrative boundary and toponym, etc.
3.4.2 Means: In order to decrease workload, three means are
adopted. (1) Indoor processing with auxiliary materials
supplied by the local government, including landuse map,
landcover map and so on; (2) Querying into the responsible or
technician of local government; (3) Checking on the spot for
the change parcels that can't be solved by two means as before.
In the investigation, it is good way to keep a computer that take
all data, if no, it is necessary to print image and table in paper.
3.5 Post-processing
According to the results in the field, false change parcels are
deleted, inaccurate polygons and types are corrected, each
change parcel is given with new attribute, including landuse
types before changing and landuse type in status, etc. Finally,
they can be mapped into different kinds maps with needs or
integrated into landuse database.
4. PROBLEM AND PROSPECT
4.1 Problem
4.1.1 change information automatic extraction: (1)
image-image combination: some methods are conservatively
effective to automatically extract change, but they have to deal
with too much noise to obtain real change, also the vector data
is not ideal after raster-to-vector conversion because of
discontinuity or roughness; (2) Image-figure combination: there
is no effective way to get change automatically at present.
Landuse status occurs great change these years since economy
develops rapidly in China, National Land and Resource
Department is just executing a plan to update landuse map with
satellite image during several years, so it is urgent to find an
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effective way to solve this problem.
4.1.2 Investigation means in the fields: For the reason of cost
and technology, most of fields works are finished by traditional
measure means to get area, width and other information of
the precision of
change parcel. In order to improve
investigation result, it is suggested to use GPS and other new
technologies in the fields.
4.2 Prospect
In the frame of nationwide land & resource investigation plan,
this project will be with great potential in the future: (1) more
and more new applications will be developed: except landuse
change monitoring and landuse map update, it can be also used
to construct and update the landuse database and cadastral
database, aid landuse plan, land conversional investigation and
cadastral management, supervise the development of national
important engineering projects, monitor the development of
disaster and provide strategies for disaster prevention, etc...
Following the developing of application, new data sources and
new technologies will be required. For ex, in order to monitor
the important construction project, the high-resolution satellite
image will be used (just as QB and IKONOS). In 2004, aerial
photography will be widely applied in cadastral map updating
and database construction, especially after integrating with
IMU/DGPS, digital camera and other new technologies.
(2) More and more cities will be brought into this project. At
first, project focuses on 93 cities with more than 500,000
populations, then it will cover more cities, since there are M
provinces or municipalities, 332 cities or autonomous states,
2860 counties or districts in China.
(3) More and more government departments and other branches
will participate in this project: the project firstly services for
center government to supervise the landuse status in macro
dimension, then the local government of provinces or cities will
forwardly apply this technology in their daily work since they
have acknowledged its benefits. More and more needs will
promote the developing of technologies, in reverse, new
technologies will popularize and deepen the applications. In
virtue of this trend, the project will construct the nationwide
landuse RS monitoring system.
References:
1999. 2000, 2001, 2002, Technical report of Landuse dynamic
RS monitoring, Chinese academy of Surveying and Mapping,
Chinese Academy of land reconnaissance and planning.
Li Yingcheng, Guo Tongying, 2002, Landuse Dynamic
Monitoring with RS Technology in China, ISPRS TC-VII
International Symposium & ISPRS Annual Convention,
Dec3-6,2002, Hyderabad, India..
Appendix 1: Working flow of landuse RS monitoring.
Internation:
BEA
Data st