I 
Ü 
13 
ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 
ON IN CHINA 
Sciences 
jlture 
Je 
uses on sustainable 
3eijing to investigate 
3 are involved in the 
>lant Nutrition, Plant 
rounding area of the 
lacro scale. For the 
, and the method of 
sen for land use 
a spatial information 
rom satellite images 
blems: 
coordinate systems 
dI points 
>f land use map 
For some maps in large scale it is very difficult or impossible to 
get coordinates or information about projection, if such 
information is available there are still problems to face. In Fig.1, 
this becomes obvious, even so it does not show only large scale 
scale data. The data do not match. 
Furthermore, for a soil and land use map which was available for 
the township in a scale of 1:10,000, the information about 
coordinates and projection was not accessible. Therefore, the 
acquisition of highly accurate x,y-coordinates for the 
georeferencing of the IKONOS2 image and of all other available 
spatial information is essential to ensure further analysis and 
enable the evaluation of the used data. 
DGPS MAPPING 
For the collection of the high accurate x,y-coordinates, a DGPS- 
system was set up for field work without relying on base stations 
or any other data source in China. In Fig.2 the components of 
the system are shown. For the GPS receiver, a GARMIN GPS 
III+ was chosen due to its small size and its high compatibility for 
DGPS receivers. Accuracy of this GPS is around 10 m since 
May 2000. The DGPS receiver itself is a Fugro Omnistar 
3000LM which operates with a 24 h satellite based DGPS 
system (www.omnistar.com). For the data logger, a small 
handheld computer, HP Jornada, with a 24 MB memory card 
was used. The Garmin GPS III+ itself can store quite a number 
of waypoints, too. Power supply for the GARMIN GPS III+ are 
AA batteries. For the OMNISTAR 3000LM DGPS, a motor cycle 
battery was used. 
Fig.2: Components of the used DGPS system 
The advantages of this system are its small size, low weight, 
independence, and high accuracy of around 2 m. The 
disadvantage is that the system is not able to store elevation 
data which have to be written down separately. The accuracy of 
the DGPS elevation measurements in the township of 
Dongbeiwang is around 5 m. Fig.3 shows the components of the 
DGPS system, too. The height of the GARMIN GPS III+ (1. in 
Fig.3) is about 12 cm not including the 5 cm antenna of the GPS. 
Units 1. to 4. in Fig.3 are necessary for the DGPS survey. Total 
weight is around 4 kg. The battery charger is for the power unit 
(4. in Fig.3) of the DGPS receiver (2. in Fig.3). The battery for 
the DGPS receiver lasts for 30-40 working hours. The notebook 
is only necessary to run special software for the first activation 
of the DGPS license. For the processing of the DGPS data and 
the creation of the polygons Fugawi3 (www.fugawi.com) and 
Arclnfo7.2.1 (www.esri.com) are used. Finally, the photo in Fig.4 
shows the DGPS system in the field during the survey in 
Dongbeiwang in late summer 2000. Further data collection is 
done in Spring 2001 for Dongbeiwang and selected areas of 
Beijing Province. 
2. DGPS receiver 
3. DGPS antenna 
Battery 
charger 
Notebook 
4. Power source 
for DGPS 
Fig.3: Photo of the components of the DGPS system 
Fig.4: DGPS system in “action” 
IKONOS2 IMAGE ANALYSIS 
The first step of the IKONOS2 image processing, which was 
ordered in GEO50 quality due to costs, is the orthorectification 
and georeferencing. The GEO50 accuracy is 50 m (RMSE 23,6 
m) (www.spaceimaging.com). Using the ground control points 
(GCOs) of the DGPS mapping, the IKONOS2 image was 
resampled with a 1 m resolution for the panchromatic file and a 
4 m resolution for the multispectral files. The accuracy is around 
2 m. This accuracy, deriving from the DGPS mapping, is 
comparable to IKONOS2 High Precision Plus data which are not 
available for China. The Software for the processing of the 
images are IDRISI32 (www.clarklabs.org) and Arclnfo7.2.1 for 
Windows2000 on a Toshiba Tecra 8000. ArcView3.2 is mainly 
used for display the results. 
In Fig.5, the results of the first image processing are displayed. 
The displayed area in Fig.5 covers the surroundings of the 
experiment field in Dongbeiwang, which covers around 15 ha. 
Some of the research plots of the field experiment are also 
shown in Fig.5 as well as the results of the DGPS mapping (red 
points and lines) and the georeferenced soil and land use map 
1:10,000 of this township (yellow lines). The GCOs of the DGPS 
mapping were also used for the georeferencing process of this 
land use map