Photogrammetry and Remote Sensing

Remote sensing when applied to land surveying generally refers to the use of sensors to acquire the geometric or radiometric information of the Earth surface or ground objects. Sensors can be classified into "imaging/non-imaging" or "active/passive" types (see examples in Table 1).

Photogrammetry is regarded as the earliest application of imaging or passive remote sensing dated back to one and a half century ago and has become a specialized stream focusing on the use of photographic images for measurement and information extraction. Nowadays, the sensor platforms for photogrammetry and remote sensing are highly versatile covering satellites, aircrafts, drones, mobile vehicles and backpack carriers. Land surveyors apply photogrammetric and remote sensing technologies widely in their specialized works ranging from mapping and land cover classification to 3D city modelling and change detection.

   Table 1: Examples of remote sensors

Sensor

Type

Digital camera

Imaging/Passive

Infrared imaging sensor

Imaging/Passive

Radar

Imaging/Active

Laser scanner

Non-imaging/Active

Sonar

Non-imaging/Active