Abstract
Both this, article II and another one, article I, titled “Geometric Quality In Geographic Information” published in this encyclopedia propose the theoretical aspects of the method to evaluate the geometric integrity of Digital Elevation Models obtained by different techniques and therefore, different stochastic hypotheses are considered. In the article I we considerer the classical topographic or aerial photogrammetry stereo images method (included ASTER or SPOT images) and we assume consistent stochastic hypotheses. In this Article II we consider IFSAR techniques and the stochastic hypotheses are specific according to the particular geometry involved in this technique.
TopNow we outline the way in which the general estimator for variances in the three-dimensional case is applied to the IFSAR-derived DEM.
Key Terms in this Chapter
Interferometric Synthetic Aperture Radar (IFSAR): A radar technique used in geodesy and remote sensing. This geodetic method uses two or more synthetic aperture radar (SAR) images to generate maps of surface deformation or digital elevation, using differences in the phase of the waves returning to the satellite, or aircraft. The technique can potentially measure centimetre-scale changes in deformation over timespans of days to years. It has applications for geophysical monitoring of natural hazards, for example earthquakes, volcanoes and landlsides, and also in structural engineering, in particular monitoring of subsidence and structural stability.
Delaunay Method: A set P of points in the plane is a triangulation DT(P) such that no point in P is inside the circum circle of any triangle in DT(P). Delaunay triangulations maximize the minimum angle of all the angles of the triangles in the triangulation; they tend to avoid «sliver» triangles. The triangulation was invented by Boris Delaunay in 1934.
Correlated Random Variables: Probability theory and statistics, correlation, (often measured as a correlation coefficient), indicates the strength and direction of a linear relationship between random variables. In general statistical usage, correlation refers to the departure of two variables from independence. In this broad sense there are several coefficients, measuring the degree of correlation, adapted to the nature of data
Advanced Spaceborned Thermal Emission and Reflection Radiometer (ASTER): One of five remote sensory devices on board the Terra satellite launched into Earth orbit by NASA in 1999. The instrument has been collecting data since February 2000. ASTER provides high-resolution images of the Earth in 14 different bands of the electromagnetic spectrum, ranging from visible to thermal infrared light. The resolution of images ranges between 15 to 90 meter. ASTER data is used to create detailed maps of surface temperature of land, emissivity, reflectance, and elevation.