SPOT 5 HRS LOCATION PERFORMANCE TUNING
AND MONITORING PRINCIPLES
A. Bouillon **, P. Gigord "
* CNES, 18 avenue Edouard Belin, 31401 Toulouse Cedex 4, France, aurelie.bouillon@cnes.fr
* IGN Espace, BP 42116, 6 avenue de l'Europe, 31521 Ramonville Saint Agne Cedex, France, patrick.gigord@ign.fr
Commission I
KEY WORDS: SPOT, Stereoscopic, Monitoring, Geometric, Performance
ABSTRACT:
HRS instrument on board of SPOTS allows acquisition of stereoscopic pairs in a single pass. This instrument has been subject of
specific attention even after the end of SPOTS in flight commissioning phase. The stake was not only to fulfil HRS' location
specification of 50 meters in root mean square but to obtain a location performance as best as possible and at least about 25 meters in
root mean square as expected before launch. Moreover, it should be checked that the instrument could cope with the realisation of
Reference3D world-wide Digital Terrain Model database, in particular for horizontal accuracy, set to 16 meters for 9095 of the
points without ground control points. The article gives an outcome of the work carried out to improve the location performance.
First, an overview of HRS will be given, with a specific attention paid to the geometric model available through ancillary data given
with the images which is the only data available to reach the location performance.
Then, methods and means used to reach the objectives will be described : French Space Agency (CNES) and French Mapping
Agency (IGN) worked in co-operation to carry on specific analyses at three levels of interpretation.
Improvements brought to the performance after the end of the image quality commissioning phase will be detailed : most error
sources have been identified and some of them reduced or removed thanks to satellite on board modification or ground models.
Finally, a view of the current location performance and a list of error sources will be detailed as a balance of the location
performance's level reached.
The conclusion will remind of monitoring principles adopted and detail further work planned.
1. INTRODUCTION A stereoscopic pair acquisition is thus possible in a single pass
with 90 s time delay between the two images (see figure 2). The
correspondent base-to-height ratio is about 0.8.
In this introduction, we will deal with general presentation of
HRS, its geometry and remind of geometric calibrations already T
carried on which will not be detailed in this article. i To + 90 seconds
1.1 Presentation of HRS
SPOTS is the latest of SPOT satellite family and one of its
novelties is an on board stereo mission with its High
-20°
Stereoscopic Resolution instrument called HRS (see figure 1). |
Rear HRS
max. 600 km
Figure 2 : HRS' acquisition process
Each camera has a focal length of 580 mm and its focal plane is
composed of a single CCD array of 12,000 detectors at 10 m
resolution, which makes a 120 km swath. Along track sampling
Figure 1 : Detail of HRS on board SPOTS rate is 5 m which provides a better resolution in the epipolar
direction. Altimetric accuracy is thus expected to be better than
5 m rms.
HRS has been designed for a DTM mass production all over the
; = ic nig c ; ^ two teles ; with an : ; s
one mw Hemet A Ron ed ef n d > em es For more details about HRS instrument, see http://spot5.cnes.fr,
ngtrack viewins angie o T [Gleyzes, 2003] and [Baudoin, 2004].
