Dem Generation by Satellite Imagery and its Accuracy
Tsuneaki Shimoji
Geographical Survey Institute
Tsukuba- shi, Ibaraki-ken, Japan
Abstract
DEMS were generated through stereo-matching technology by using stereo satellite imagery of JERS-1 OPS and SPOT HRVdata. These data were evaluated by comparing them with existing DEMs derived from topographic maps. The accuracy was compared in the following two cases; (1) basically relying on satellite position and attitude data, (2) with many GCPs. The effect of pre-processing to original images was found effective for removing large errors caused by mismatching around mountains tops.
1. Introduction
Three dimensional measurement of satellite images can be done by stereo pair images of SPOT and JERS-1 through comparing them with existing DEMs several cases are compared in view of target area's topography and existence of image pre-processing and so on.
2. Test Sites
2.1Test data
We selected test data where there are few clouds in the area so that matching accuracy is not influenced, and where are equally distributed mountains, valleys and hills. Test data used for both satellite are listed in
Table1 and 2.
Table 1. Test Data Used for SPOT Satellite
| |
Left image |
Right image |
| Sensor |
HRV-P |
| wavelength |
0.51 µ m~0.73 µ m |
| Path -row |
328-279 (Minobu) |
| Date |
1992.11.12 |
1992.11.16 |
| Pointing Direction |
R 17.2 Degrees |
L 20.9 degrees |
Table 2.Test Data Used for JERS-1
| |
NadirLooking image |
ForwardLooking image |
| Sensor |
OPS |
| Scene name |
Tokyo |
Nikko |
| Path-Row |
65-241 |
65-239 |
| Date |
1993.3.9 |
| Process level |
L1 |
2.2 Test Sites
The following test sites were selected: A and C areas are gentle slope with plain and hills, B and D areas are severely mixed with valleys and ridges where condition of accuracy test is comparatively hard. E area was added for evaluation in JERS-1 The sizes of test areas are about 15km. In length, and figures of test areas are rectangle DEM points for accuracy verification were 90000 points for each test site.
Contour lines of test site B and D are shown in Figure 1 and 2. Respectively the data used for each test site are shown in table 3. Average and Standard deviation of table 3 were calculated from DEM of Digital Cartographic Data derived from 1:25,000 topographic map.
Figure 1: Contour Lines of test site B
Figure 2: Contour Lines of test site D
Table 3 Test Data Used for Test Site of Both Satellite
| Satellite and Test Site |
North West Corner |
South East Corner |
|
| Latitude |
Longitude |
Latitude |
Longitude |
Average |
S.D |
| SPOT |
A |
N35° 34´05" |
E138° 24´35" |
N35° 22´50" |
E138° 32´05" |
503.17 |
238.75 |
| B |
N35° 21` 08" |
E138° 04´41" |
N35° 13´38" |
E138° 15´ 56" |
1448.39 |
402.86 |
| JERS-1 |
C |
N35° 40´00" |
E139° 07´ 30" |
N35° 32´30" |
E139° 18´ 45" |
320.00 |
142.50 |
| D |
N35° 40´45" |
E138° 56´30" |
N35° 33´30" |
E139° 07´45" |
537.41 |
205.69 |
| E |
N35° 32´30" |
E139° 03´45" |
N35° 25´00" |
E139° 15´00" |
804.49 |
301.00 |
