JAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India, 2002 
3. RESULT enough to keep the tracing line within a pixel. 
3.1 Precision 
3.2 Statistics and Analysis 
The precision of DRG is better than 0.5-1m. The mean error of 
image rectification and matching is less than one pixel (10 The area data of marsh in Tianjin between 1999 and 2001 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
meter). When tracing spot outlines, the image is zoomed in listed in the following Table2 
unit: Km? 
COUNTRY RIVER MANMADE POOLS SWAMP LAKE LAGOON 
1999 2001 1999 2001 1999 2001 1999 2001 1999 2001 
TANGGU | 27.5 27.5 375.7 376.1 81.4 81.4 
HANGU 9.3 9.3 189.5 192.2 44.9 44.9 
JINNAN | 16.1 16.1 49.8 50.4 
DAGANG | 23.8 23.8 238.5 255.3 22.0 22.0 
DONGLI | 8.2 8.2 78.2 81.4 
BEICHEN | 13.1 13.5 25.3 27.5 
WUQING | 16.7 16.7 71.8 73.6 
JIXIAN 13.3 13.3 19.1 20.4 0.5 0.5 59.2 59.2 
BAODI 34.8 34.8 3.9 59.1 6.8 6.8 
XIQING 6.2 6.2 106.2 107.0 3.7 3.7 
JINGHAI | 19.5 19.5 56.2 |» 60.6 2.3 2.3 
NINGHE | 26.1 26.1 94.4 94.0 50.8 50.8 
MIDCITY | 4.2 4.2 16.8 15.4 
TOTAL | 218.8 219.2 | 1325.4 | 1412.9 | 161.6 |161.6 | 59.2 59.2 50.8 50.8 
CHANGED 0.18% 6.60% 
  
  
  
  
  
  
  
  
Table 2. Marsh Area in Tianjin 
The table shows that the river total area has grown little from 
1999 to 2001. It is because the rainfall is higher in 2001 than 
1999 that the waterline became higher along which we 
calculated the river area. 
Many counties are sited at the bay of Bohai sea where enriches 
  
Figure 2. Swamp in 1999 
water resources suitable for breeding aquatics. Some swamp was 
exploited to manmade pools during last two years. That is the 
reason of manmade pools area has been increased. Just like what 
shows within the green polygon in Figure2 and Figure3. 
  
Figure 3. Manmade Pools in 2001 
The statistic data of city renovation and expansion is listed inTable3: 
  
  
  
  
unit: km? 
1999 2001 
SITUATION SITUATION AREA 
Farmland City Expansion 2.4 
Non-Farmland City Expansion 2.1 
City Building(old) City Building(new) 4.2 
  
  
  
  
  
  
Table 3. Changed Area of City Expansion and Reconstruction 
Figure4 shows the building renovation in Tianjin city. The 
buildings within the orange outline in the left image of 1999 
were old bungalows that had been changed to new storied 
buildings in the right image of 2001. 
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