The laser survey is based on Lidar system, i.e. consists of using a laser transmitter-receiver pair to make a surface scan of the terrain in order to obtain a digital representation of the topography of the area of study. It is also possible to obtain geo-referenced digital pictures, called orthophotos , using a digital camera of high resolution attached to the system. The Lidar system is mounted on a specially conditioned airplane, whose trajectory will be determined by a high precision GPS control located at known coordinates. The high point density that can be measured using this system and the high resolution that can be obtained, turn it into a powerful tool for basic and detailed engineering studies over important civil projects, roadworks, infrastructure, mines, etc. A main difference with the traditional methods is the fact that the information does not depend only on the photographs, and so it is not affected by terrain variations, light or shadow conditions, etc. Data processing allows generating maps at different scales and georeferenced in different coordinates systems. It also allows to get plannimetry, contour lines, data models (DMT), structure and buildings outline, etc. The main advantages of this technology compared to the terrestrial methods are the capacity of covering great extensions of terrain in small amounts of time, to reach high risk places without danger for the workers, complement the acquired information with high quality photos and finally craft a map in any scale with the data of the same flight.
