The acquisition of raw data is the first step for the generation of processed, complex products.
Helica provides the client with raw data, if the client owns the technical tools and the knowledge for an autonomous processing, or with processed and ready-to-use data, after a complete in-house processing.
The raw data acquired by Helica are the following:
Laser intensity images allow the understanding of the physical characteristics of reflectance that are typical of a given surface. For each pulse, there is a registration of its coordinates and reflectivity, which depends on the type of object: asphalt, roofs, soil, vegetation, water etc.
The point cloud is composed by all the returns per every emitted pulse. These data provide the following information:
- geographical coordinates (x,y,z) of the return pulse (position and elevation);
- intensity of the return;
- GPS time.
The geometrically corrected and georeferenced data of the point cloud represent the input for the generation of digital elevation models (DEM).
The laser pulse emitted from the sensor on the aircraft comes up against many objects before reaching the terrain. The first-return, for example, measures the distance to the first target the laser pulse encounters. Therefore, there are numerous returns. ALTM 3100 EA and Gemini (the systems produced by the Canadian company Optech) register up to 4 returns.