SPOT 5 Builds a Global Multi-Purpose 3D Database: Reference3D
ABSTRACT
The successful launch of the SPOT 5 satellite on May 3rd, 2002 can be seen as a milestone for
DEM and 3D daases, because its payload includes HRS, a stereoscopic imaging instrument
which collects large strips of stereo data (120 by 600 km). After 2 years in orbit, HRS has
acquired more than 70 millions km˛ of cloud free data, which is progressively processed into a
3D daase named Reference3D.
Reference3D includes a DTED level 2 DEM and an imagemap, secured by exhaustive quality
and insurance procedures. It opens an easy and affordable access to qualified and homogenous
elevation data over large areas, exactly the kind of very useful data (“basemap”) which
procurement was highly problematic in the past.
The paper briefly describes the HRS sensor on-board SPOT 5, and then presents the quality
insurance procedures that guaranty the meeting of ambitious requirements, and the accuracy
assessments performed by independent labs (ISPRS, NGA, …)
Finally, the paper shows some of the various applications of such homogenous and large-coverage
daase, focusing on middle-scale mapping.
1. INTRODUCTION
SPOT5, the fifth satellite of the SPOT remote sensing satellite family was successfully launched
on the 4th of May 2002. SPOT5 ensures continuity of data acquisition and space image services
but also to provides users with advanced products. It flies two identical cameras named HRG
(High Resolution Geometry) providing a 2.5 m and a 5 m resolution in a panchromatic mode
and a 10 m resolution in a multi-spectral mode, still keeping a 60-km ground field. Stereo
application complements SPOT5 mission ; the satellite flies a specific High Resolution Stereo
instrument (HRS) made up of two telescopes allowing a 20° fore view and a 20° aft view over a
120-km swath, sampling the landscape every 5m. HRS was designed to build up a worldwide
digital elevation daase called Reference3D covering 30 to 50 millions km˛, one third of the
globe’s landmasses, in five years. Its remarkable ability to acquire stereopairs is a huge step
forward not only for production of high-quality digital elevation models (DEMs) to map relief,
but also for automatic production of orthoimages of unrivalled geometric accuracy.
Reference3D is the result of a dual-use civil/military programme designed to very strict
specifications.
