International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B1. Istanbul 2004 
2. DATA 
Within the Initiative, CNES and DLR Oberpfaffenhofen 
provided the data set number 9 (Chiemsee), consisting of: 
e two stereo images from SPOTS-HRS sensor with 
corresponding metadata files; 
e the description of the exact position of 81 object points in 
Germany, measured with surveying methods; 
e reference DEMs produced by Laser data and conventional 
photogrammetric and geodetic methods. 
In the next paragraphs the main data characteristics are 
reported. 
2.1 SPOT-5/HRS scenes 
The two stereo images were acquired on 1% October 2002 in 
the morning from 10:15 to 10:18 (forward) and from 10:18 to 
10:21 (backward) over an area of approximately 120x60 km? in 
Bavaria and Austria. 
Each image is 12000 x 12000 pixel large, with a ground 
resolution of 10m across and 5 m along the flight (parallax) 
direction. The scenes were acquired in panchromatic mode in 
stereo viewing along the flight direction with a base over height 
ratio of 0.8. The two telescopes contained in the HRS 
instrument scan the ground with off-nadir angles of -20 degrees 
(forward image) and 120 degrees (backward image). Each 
telescope has a 580 mm focal length and a focal plane with a 
CCD line of 12000 pixels, 6.5 um size. The main sensor 
characteristics are reported in Table 1. 
The scenes cover an area with flat, hilly and mountainous 
(Alps) terrain, agriculture areas, towns, rivers and lakes. The 
height ranges between 400 m and 2000 m. Clouds are absent 
(Figure 2). 
The metadata files contain information on the acquisition time 
and image location, ephemeris (sensor position and velocity 
from GPS at 30 seconds time interval, attitude and angular 
speeds from star trackers and gyros at 12.5 seconds interval), 
sensor geometric (detectors looking angles) and radiometric 
calibration. For a detailed description of the metadata file see 
DIMAP site. The on-board determination of the satellite 
position and the absolute dating are supplied by DORIS 
(Doppler Orbitography and Radiopositioning Integrated by 
Satellite). 
DORIS is a one-way microwave tracking system developed for 
precise orbit determination (1m RMSE) by GRGS (Groupe de 
Recherches de GFodEsie Spatiale) and IGN (Institut 
GFographique National). The concept is based on a ground 
segment (of globally positioned tracking stations) and a space 
segment (i.e. DORIS as a passenger payload in a satellite 
consisting of a receiver, an ultra-stable oscillator and an 
antenna). There is also a control centre as part of the ground 
segment, located at CNES (Gleyzes et al., 2003). The onboard 
receiver measures the Doppler shift of uplink beacons in two 
frequencies (fl1 = 2036.25 MHz, 2 = 401.25 MHz), which are 
transmitted continuously by the DORIS ground network of 
stations. One measurement is used to determine the radial 
velocity between spacecraft and beacon, the other to eliminate 
errors due to ionosphere propagation delays. 
   
Table 1. SPOT5-HRS characteristics (Source CNES). 
  
  
  
  
  
  
  
  
  
Mass 90 kg 
Power 128W 
Dimensions Ix 1.3x0.4m 
Field of view 8 
Focal length 0.580 m 
Detectors per line 12,000 
Detector pitch 6.5 um 
Integration time per line 0.752 ms 
Off-nadir angles: 
-forward 20] 
-backward -20f 
  
Spectral range (PAN) 0.49 um - 0.69 um 
  
Ground sample distance: 
  
-across track 10m 
-along track 5m 
Modulation transfer > 0.25 function 
  
  
  
Signal-to-noise ratio 7 120 
  
  
     
a 
+ 
Figure |. SPOT-5/HRS along-track image acquisition 
(Source: CNES). 
2.2 Reference DEMs 
The reference DEMs provided by DLR Oberpfaffenhofen are: 
e 4 DEMs in southern Bavaria (Prien, Gars, Peterskirchen, 
Taching) created from Laser scanner data with a point 
spacing of 5 meters and an overall size of about 5 km x 5 
km. The height accuracy is better than 0.5 m; 
e | DEM (area of Inzell, total: 10 km x 10 km, 25 m spacing) 
partly derived from laser scanner data (northern part, height 
accuracy better then 0.5 m) and partly derived from contour 
lines 1:10 000 (southern part, height accuracy of about 5 
m) 
e. A large coarse DEM (area of Vilsbiburg, 50 km x 30 km) 
with 50 m spacing and a height accuracy of about 2 meters, 
derived by conventional photogrammetric and geodetic 
methods. 
In Table 2 the principal characteristics of the reference DEMs 
are summarised. 
  
  
    
   
    
   
   
   
    
   
    
     
      
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   
   
   
   
   
   
   
   
     
   
   
   
   
   
   
    
    
  
  
   
Inte 
  
Figui