As seen in previous chapters, surveying measurements for determining the values of geospatial data are most often performed using terrestrial instruments and in direct contact with the measurand. Depending on the size of the site and the number of objects to be measured, this work may be laborious, costly, and, in some cases, even unfeasible with the technology currently available. This type of measurement can include cadastral surveys of large areas, cartographic mapping, mapping of corridors for linear engineering projects, mapping of difficult access areas, data collection for digital terrain model (DTM) or digital surface model (DSM) generation of large areas, and many others.