Advantages and Disadvantages of LiDAR: LiDAR with Photograph Information (Especially for GATE-Geospatial 2022)

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Advantages of LiDAR

  • The main advantage, which has already been mentioned, is the ability to obtain a DSM, with an accuracy of decimetres, and with a lower cost than using conventional photogrammetric techniques.
  • One of the advantages of LiDAR technology is the possibility of measuring, for each pulse, the first and last rebounding of the beam that goes back to the plane. This allows measuring the height of the ground in areas which are completely covered with vegetation, and which are not possible to be measured with conventional techniques such as photogrammetry.
  • The achievement of the DSM is almost direct. The only operation to be performed, in most cases, is the relative orientation of the flight strips, or the georeferentiation into a given reference system.
  • The flight can be performed some more days a year. As it is an active sensor, it does not need any sunlight and it can fly during the day, at night or even with high clouds. As we have seen, in conventional photogrammetry, a certain height of the sun and completely clear days are needed.

LiDAR Presents Two Limitations

  • Firstly, data collection of points not belonging to the Earth field as vegetation, buildings, electric lines, etc. is difficult. The treatment used is filtering the elements that do not belong to the Earth, to go from DSM to DEM; this process is done manually by identifying and removing points. Currently, some algorithms are being studied to make this process more automatic.
  • The second disadvantage is the lack of information from the visible spectrum. We do not get an image as usual, which makes it difficult to identify the terrain՚s elements. This is a disadvantage because, although the laser provides the intensity of the reflected rays, it is difficult to identify the elements they correspond to. Therefore, it is appropriate to combine these data with digital photo sensors, which arrange information, invisible bands.

Overall Working

In this way, the future goal is to combine the information acquired by both sensors: LiDAR information, which delivers high geometric accuracy, and aerial photography information, which provides continuous information of the earth field, and good metric information.

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