HRS instrument on SPOT 5 is dedicated to simultaneous stereopairs acquisition:

• 2 telescopes, one pointing forward and one aft of nadir, at a fixed angle of 20°
• acquisition interval: 90 seconds along the track
• an imaging swath of 600 km x 120 km (72,000 km2)
• base/height ratio (B/H) of 0.8

A digital elevation model (DEM) is a file containing elevation values distributed on a uniform grid of an area of interest.
SPOT DEMs are produced by automatic correlation of stereopairs acquired by HRS

Reference3D is a global, geocoded database developed jointly by Spot Image and the French mapping and survey agency, IGN.

It is the foundation for any application that relies on very-high-quality elevation databases. It contains three layers of information:

• HRS DEM
• HRS orthoimages
• quality and traceability data