Remote sensing versus field mapping

In comparison to terrestrial field mapping and observations on the ground, EO-based humanitarian response benefits from general assets of remotely sensed data:

From a distance. The core principle of remote sensing data, its obtainment from indirect contact with the object of concern, is critical to crisis-related applications. Often the area affected by the crisis is inaccessible or difficult to reach or from a security point of view too dangerous to enter. This means that information derived from remote sensing is the only information available.

Area-wide coverage. Depending on the spatial resolution, areas can be covered with variable extent, under the same imaging conditions and characteristics. The trade-off between resolution and extent is thereby a limiting factor that is also reflected in costs and timeliness of data provision.

 Global availability. Satellite data are globally available with a theoretical cover rate of some 95% of the inhabitable space of the globe and factually 100% of the permanent settlement area. Note that cloud cover (e.g. in tropical latitudes) is a limiting factor for data acquisition and analysis.

Retrospective view. Time-series not only enable constant monitoring in future time steps, but also ex-post assessments by past sequences. This is a key factor for estimating detected trend patterns in a more reliable matter.