Abstract
Onboard SPOT 5, the HRS instrument systematically collects 600 km × 120 km stereopairs around the Globe since 2002. From this time, SPOT5 stereoscopic imagery becomes one of main satellite data sources for accurate DTED level 2 DEM extraction.
Spot Image and French National Cartographic Institute (IGN) decided in 2002 to build a worldwide accurate database called Reference3DTM using HRS data. Huge eorts have been made to standardize the process in order to oer aordable prices. Until 2008, the targeted accuracies were 16 mCE90 for horizontal accuracy, and 10 mLE90 for vertical accuracy. These accuracy requirements were achieved without any control points nor map support.
The introduction of the paper briey reminds the most signicant assessments performed by major players within the geospatial community, and more specically the one by ImageONE Co., Ltd. (Tokyo) on two Reference3D geocells over the Northern coast of Japan, Hokkaido province. This work was published in 2008 during the last Beijing ISPRS congress.
In 2009, it was decided to introduce reliable GCPs within the Reference3D production process, to increase the horizontal accuracy down to 6-10 mCE90. In addition, two new layers were added to the product, which provide the user with i) the horizontal accuracy for every single pixel of the Reference3D orthoimage and ii) the vertical accuracy for every single elevation value within the Reference3D DEM.
The paper shows how the extensive use of ICESat data brings valuable information regarding the eective vertical accuracy, and how ICESat data allows to quantify the elevation accuracy of a dataset.
In conclusion, we present the road map for the update of the whole Reference3D database, which currently spreads over more than 45 millions of sq. km. (being more than 4,200 1° by 1° geocells), already funded and started up to 2014, towards 80 Mkm2 of Reference3D products.
