JO; 
À Photomap of China with NO 
Huang Qian (Lecturer? 
Remote Sensing Lab. China University of Geosciences 
Wuhan, Hubei, 430074 P.R.China 
ISPRS Commission IV. WG.1V/2 
HuangRentao (Professor), ZhangXinchang (Lecturer) 
Department of Mapping 
Wuhan Technican University of Survey and Mapping 
Wuhan, Hubei, 450070 P.R.China 
ISPRS Commission IV. WG.1V/2 
LaiRongqing (Engineer 
ZhuHuiming (Engineer) 
Guangzhou Satellite Meteorological Ground Station 
Guangzhou, Guangbohg, 510640 P.R.China 
ISPRS Commission IV WG.IV/2 
ABSTRACT 
A low-cost and quick mapping technigue on near- 
synchronous, small-scale and macrocosm is developed 
using digital NOAA/AVHRR data. The photomap of China 
on the scale of 1:4,000,000, is made from imagery 
and symbol base maps according to cartographic 
techniques strictly. The false color composite of 
AVHRR thermal infrared, near infrared and visible 
red channels is used to provide much information and 
colourful tones. The data processing include map 
projection transformation, image enhancement both on 
contrast stretch and image sharpening, color balance 
adjustment, cloud removing, separated processing of 
land and sea, modification of image seasonal aspect 
with vegetation index image and mosaic. The data was 
received by the meteorological satellite ground 
station in Guangzhou in the late autumn and the 
early winter from 1988 to 1991. This is the first 
small-scale, integrated and standard color photomap 
in China, especially it contains the whole South 
China Sea that is rather difficult or expensive to 
use other remotely sensed data such as Landsat or 
SPOT. Geographic element, map symbo! and lettering 
were selected and designed carefully considering the 
finial load of the photomap content and vision 
effect. This photomap is very useful not only in 
remote sensing or geosciences application but also 
in many other fields. 
Key words: Cartography Image Processing Mapping 
Space Imagery NOAA/AVHRR Photomap 
INTRDUCT | ON 
Photomap is an important field in cartography. Most 
of photomap were made with erath resource satellite 
system, such as Landsat or SPOT. But, for mapping 
a small-scale photomap, it is often neglected that 
NOAA AVHRR, sometimes, is a suitable and low-cost 
mapping data source of remote sensing.  !n China, it 
is impossible to use Landsat MSS or TM data for 
mapping the integral China. There are two reasons. 
The first is absence of the data of South China Sea 
and the parts of Northwest and Southwest China 
because of the limited ground receiving radius of 
the remote sensing satellite ground station in 
Beijing. The second is higher cost for processing 
So much data if a digital mosaic operation is 
performed.  AVHRR is an easy-obtained, low-cost and 
high view frequency remote sensing data although its 
ground resolution is lower (1100 meters in nadir). 
Its larg view field and related small data volume 
are advantageous to the digital mapping operation 
economically. Also, the high view frequency of 
AVHRR is useful to get a high quality and cloud- 
free image with a cloud removing technology. 
Therefore, a high quality, near-synchronous and 
low-cost photomap on small scale can be achieved. 
The photomap was designed and made according to 
the national cartographic standard strickly. 
Albers equal-area projection was used as the 
mathematical foundation. The two paral lel 
latitudes were located in northern latitude 25 
and 47 degrees respectively as well as most 
published map of China. Geographic elements, map 
symbols and letterings were selected and designed 
careful ly considering the finial load of the map 
content and vision effect. Three of AVHRR 
channels, thermal infrared channel 4, near 
infrared channel 2 and visible red channel 1, that 
were assigned to red, green and blue color 
respectively, were used to form a false color 
composite image. This composite fashion is more 
colorful than the general standard composite with 
near infrared and visible bands only. The process 
of digital image processing ensured a smooth 
mosaic without any artificial marks and the 
precise, artistic image base map (See Fig. 1). 
DATA COLLECTION AND PREPROCESSING 
This is the first step in cartography of photomap. 
The most of image data was collected by Guangzhou 
satellite meteorological ground station and the 
other was from Xinjiang and Beijing ground 
stations. The receiving period was selected in the 
autumn and the early winter from the end of 1988 
to the early 1991. In consideration of the ground 
resolution of AVHRR and the finial image 
subjective quality of the photomap on the scale of 
1:4,000,000, China was divided into 64 subimages 
that each was the size of 512 by 512 pixels and 32 
pixels overlap to adjacent ones. These subimages 
were encoded according to their geographic 
locations so that the multitemporal and registered 
image data were obtained to remove cloud cover or 
improve the image quality by combination. Most of 
the image were restricted within about 1024 pixels 
wide on a satellite nadir path in order to avoid 
the degradation of the image resolution on the 
sides of a path. The original AVHRR data was 
converted from 10-bit to 8-bit byte for display. 
Normally, the lower 8 bits of the original data 
* the project supported by National Natural Science Foundation of China (NSFC) 
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