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maps rectification or matching. change information extraction.
2.1.1 Data Resources Collection: Several kinds of data may be
used in landuse investigation. such as satellite images. aerial
photo images. control materials. land use maps or land-use
database and ete. But how to select RS data feasibly from so
many kinds of images is one of the most important items in this
study project.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004
Chinese counties are classified into four classes by analvzing
cach county's topography feature. economy development
structure. arca or range. and other attributes. Which kinds of RS
images can be selected for some county land use investigation
has been concluded in below table 1.
County class County character County Area Examples Recommending
Images
l'irst Economy developed most | <300Km” Beijing. Shanghai. Most of | Ikonos. QuickBird
quickly Province Capital
Land use changed most
quickly
second Economy developed more | 300-1000Km^ | County. or city lies on the | Arial Photo images
quickly sides of main traffic. and etc.
Land use changed more
quickly
third Traffic inconvenience 1000-3000 Guizhou Province. SPOTS
Economy undeveloped Km“ West of Xichuan province
Land use changed slowly
Fourth l'ewer residence. >3000Km” Qingzang tableland. ETM+
Land use changed scarcely Basin of Caidamu
or hardly
Table 1. RS Images Recommended for Different County
2.1.2 Change Information Detection and Extraction: There
are five schemes on detecting land use change with RS
technology according to which kinds of images data can be
obtained around the same arca. Scheme one is having both
history and current year high resolution images. Scheme two is
having history and current year middle resolution images.
Scheme three is having current year high resolution images and
history middle resolution images. Scheme four is having history
high resolution images and current year middlle resolution
images. The last scheme is having only current year high
resolution images.
Image High Resolution Middle Resolution
Image Image
Scheme History Current History Current
I Vv Jv
2 Jv J
3 J/ J
4 / v
5 J
Table 2. Different Schemes for Different Images Obtained
How to process these images and which kind of GPS will be
used for different schemes will be talked about at the following
content.
Schemel- Having Two Phases of High Resolution Images:
One of the two phases of images must be otho-rectified to the
geodetic coordinate system with control materials firstly. The
other one arc matched to it. Then change information can be
detected by overlaying them together. Images resolution is
higher enough that its geometric accuracy can fit the needs of
scale 1:10000 land use maps. But its land use category can not
be identified perfectly right. So. one of' investigation tasks on
the fields is to make up the omitted change spots. and the other
main object is to check the spots category identified right or not.
Navigation GPS with less than 10m precision will be ok.
The advantage of this scheme is that almost all of the change
spots can be detected in doors and the geometric accuracy of
their borders is suitable for mapping. But the shortcoming is
that it will spend more money and time to buy and process
images.
Scheme2-Having Two Phases of Middle Resolution Images:
Images processed. flow also includes otho-rectification.
matching and overlaying. The difference is that land use maps
will be rectified and overlayed on these two phases of images.
Because of limited by images! resolution. the geometric
accuracy of changed spots border are not so good enough to
satisfy with the needs of scale 1:10000 map. So. many small
change spots may be missed. At this time. the main object of
investigation on the fields is to obtain spots” border coordinate
surveyed with DGPS (Difference Global Position System)
technology. And their attributes like land use category should
be inquired as well.
This scheme gives a good advice that using cheaper middle RS
images to find change area and surveying their border points’
coordinates with DGPS. The images are cheaper and processed
more simply and conveniently than higher ones. But surveying
and post-processing by DGPS is more complicatedly.
Scheme3)-Having Current High Resolution Images and
History Middle Resolution Images: Higher resolution images
must be otho-rectified firstly. Middle resolution images are
rectified referencing to the higher one. Secondly. the two
matched images are merged together. Change information will
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