Emergency & Security

Satellite imagery nowadays is operationally and systematically employed when man-made or natural disasters strike. Their main advantage consists of almost instantaneous and area-wide acquisition of information, even over remote areas. Its usage though encompasses the complete disaster risk management cycle, i.e. from disaster respond over damage assessment to reconstruction activities. Often, satellite imagery acquired over disaster areas is complemented by higher resolution aerial imagery in order to obtain more detailed information about damages. 
Whereas NPOC Switzerland coordinates satellite image acquisition and analysis, its organizational host swisstopo operates planes and digital cameras. Through this constellation a multiscale approach in damage assessment is assured.

Land-slide affected area in Valais
Pre-disaster (left) and post-disaster (right) aerial imagery over land-slide affected area in Valais after heavy rainfalls in October 2011. Comparison allows for detection and assessment of damages

In 2010 NPOC contributed to image-based detailed damage assessment after a terrifying earthquake hit Haiti and its capital Port-au-Prince. This damage assessment was carried under the lead of UNOSAT, the UN Satellite Applications Programme, the EU’s Joint Research Center (JRC) and The World Bank.

Earthquake affected area in Port-au-Prince
Pre-disaster satellite image (left) and post-disaster (right) aerial imagery over earthquake affected area in Port-au-Prince. Destroyed and damaged buildings were assessed by comparison

Land displacement monitoring 

Small terrain displacements can be detected and monitored over long time periods exploiting interferometric stacking techniques based on Synthetic Aperture Radar (SAR) data obtained from spaceborne platforms. Operational terrain displacement maps are delivered by sarmap with proven accuracies on the order of one mm/year, from which average displacement rates can be obtained. The availability of long-term SAR data time-series makes it additionally possible to monitor the terrain evolution, and to differentiate among various (e.g. linear vs. non linear) behaviors.

Average displacement rate
Average displacement rate (color scale between -15 and +5 mm/year) of an area around the cities of Tokyo and Chiba, Japan, derived from PALSAR data in the period 2006-2010. Whole area (left), a region of terrain compaction over landfill (center), and uplift due to excess water injection after natural gas extraction (right).

Diagram of Terrain movements
Terrain movements for a given area showing different temporal behaviors, as obtained from Interferometric stacking techniques. Quasi-linear height change (left) and non-linear height change (right); vertical scale in [mm].