Apllication assessment of multi-level Remote Sensing and multi source informationin theinvestigation of forest resources
Contrast of Geometric accuracy
When the forest resource investigation of an average scope is made with the scale 1/250.000--1/50,000 map the optical correction satellite image controlled by a topographic map in general can satisfy the requirement of area accuracy the contrast of the following geometric accuracy is conducted on the requirement of area accuracy the contrast of the following geometric accuracy is conducted on the image only by optical by correction on the premise that the displacement of image pints and the error of geometric accuracy analysis of image line segment measurement are taken as the item of accuracy assessment in the analysis.(Table 2-5)
Table 2 Accuracy table of line segment length measurement
in hilly area on TM image.
| Order number |
1:5ten thousand length of topographic(m) |
1:4ten thousand length of TM image(m) |
D-value |
D-value square |
Measurement accuracy |
| 1 |
3190 |
3196.00 |
6.00 |
47.33 |
99.7% |
| 2 |
3550 |
3577.8 |
27.89 |
772.84 |
99.2% |
| 3 |
4540 |
4596.96 |
33.94 |
1091.64 |
99.3% |
| 4 |
5545 |
5589.2 |
44.20 |
1953.46 |
99.2% |
| 5 |
3895 |
3054.0 |
40.52 |
1641.87 |
98% |
| Total |
|
| |
5507.33 |
|
|
Mf= ± 33.188 |
Table 3 Accuracy table of line segment length measurement
in hilly area on SPOT image
| Order number |
1:5ten thousand length of topographic |
12,5ten thousand length of TM image |
D-value |
D-value square |
Accuracy |
| 1 |
6000 |
5953.2 |
46.8 |
2190.3 |
99.2% |
| 2 |
2190 |
2182.0 |
27.89 |
63.60 |
99.6% |
| 3 |
2725 |
2755.3 |
33.94 |
918.1 |
99.9% |
| 4 |
2950 |
2964.3 |
44.20 |
294.5 |
99.5% |
| 5 |
450 |
442.3 |
40.52 |
51.8 |
99.4% |
| Total |
|
|
|
3424.5 |
|
|
Mf = ± 26.17 |
Table 4 Accuracy analysis of area measurement of TM image
and 1"30.000 color infrared aerial photograph
transfer photo area
| Order number |
Land type |
1:30.000 color infrared transfer area(ha) |
1:40,000 in transfer area(ha) |
D-value |
Accuracy% |
| 1 |
Robinia pesudoacaia |
2.75 |
3.04 | 0.29 |
98 |
| 2 |
Conifer |
12.0 |
12.17 | 0.17 |
98.6 |
| 3 |
Bare land |
33.0 |
32.0 | 0.10 |
99.7 |
| 4 |
Brush |
5.0 |
4.5 | 0.50 |
90.0 |
| 5 |
Deciduous forest |
19.5 |
19.2 | 0.30 |
98.5 |
| 6 |
Field |
37.0 |
37.2 | 0.30 |
99.27 |
| Average accuracy |
96.0% |
Table 5 Accuracy analysis of measured area on SPOT image and
1/250,000 orthophotograph area
| Order number |
1:25,000measured on orthophotograph |
1:12,500area on SPOT image |
Area D-value |
Accuracy % |
| 1 |
8.75 |
8.7 |
0.05 |
99.5 |
| 2 |
9.5 |
9.4 |
0.1 |
98.9 |
| 3 |
3.2 |
3.27 |
0.07 |
97.8 |
| 4 |
31.5 |
31.20 |
0.30 |
99.0 |
| 5 |
2.1 |
2.0 |
0.1 |
95.27 |
| 6 |
7.0 |
7.2 |
0.2 |
97.27 |
| Average accuracy % |
97.37% |
Geometric accuracy of national land resource satellite image is measured with two forms 19.4 cm * 23cm and 167cm *19.4 cm the image of 19.4 cm *23cnm are divided into four parts central middle top bottom right top bottom and left top bottom error in central part is the slightest middle top bottom 2.5-7% right top bottom 5---9% left top bottom 3.11% on the ling strip image of 167 cm * 19.4 cm with the central points as the centre of the circle and the radius of 5cm 16 concentric circles of equal space length are made the geometric accuracy of each concentric circle is measured according to the sequence of top middle bottom the result is that error in the central part is about 2.2-2.4% that in the fifth concentric circle is about 4-8% and error in the edge part of the sixteenth concentric circle is maximum higher than 30%.
From the above it can be seen that both TM and SPOT have higher geometric accuracy the geometric accuracy of the national land resource satellite image without correction is lower and that the distribution of error varies with the changes of altitude distortion and topography.
