What is the density at which PS are generally retrieved?
In urban areas PS are retrieved with high density, even more than 500 PS/km2. Density decreases in countryside (about 150 PS/km2) and is lowest in mountain areas, where on average 20 PS/km2 are found. In some cases of landslides, where the terrain is covered with rocks and gravel, about 150 PS/km2 have been retrieved. To apply the Technique, at least 4-5 PS/km2 must be retrieved, otherwise it becomes impossible to correct the data for atmospheric effects.
