LiDAR Applications

From SEG Wiki
Revision as of 23:08, 1 December 2018 by Jrenner225 (talk | contribs) (→‎Other Geoscience Applications)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search
ADVERTISEMENT
Figure 1 A common ground based LiDAR unit mounted on a tripod. This is very similar to the device used at the University of Oklahoma. It can easily be transported from station to station to scan the surface of interest.[1]

LiDAR stands for Light Detection and Ranging. It is a laser ranging and detection system that measures distances and is used for mapping the surface features of the Earth. There are actually three main systems that make up a LiDAR system and enable it to work properly. There is the LiDAR itself which sends out pulses to the earth which gives the distance (hence “Ranging”) to the target that is being scanned. Then a GPS (Global Positioning System), which is used to give the location of the LiDAR device that is scanning the area. The third system is the IMU (Inertial Measurement Unit) which is used to measure the pitch, roll and heading of the LiDAR device, which is mainly for Aircraft LiDAR devices to calibrate for the position of the plane in the air with relation to the ground. LiDAR data can be collected using airborne, mobile and terrestrial methods. What truly makes LiDAR a unique and valuable tool in Geology and Geophysics is that it has the ability to map surface features on the Earth and cut through vegetation so long as light can reach the bare surface. [2]

Geoscience uses

[3]Figure 2 Aerial LiDAR image that has been collected and processed. The image on the left is with vegetation and the image on the right is with vegetation removed.

Cost Saving

LiDAR is a tool that is applied in many different industries including agriculture, GIS, automotive, environmental as well as Geophysics.  There are many universities such as the University of Oklahoma and many companies such as Sander Geophysics that use LiDAR for Geoscience. Sander Geophysics (SGL) uses LiDAR for things such as high-resolution digital terrain models that can be used in Geotechnical analysis. SGL will first scan the terrain and then remove the vegetation when analyzing the data to produce a clearer picture of the surface geology (see Figure 2).[3] From here, this type of data can provide immense cost saving in terms of seismic acquisition and processing. With the increasing complexity of seismic acquisition projects on land, having the ability to do flyover LiDAR and scan the area of interest is huge. This will provide the high-resolution digital terrain model needed to pre-plan the most feasible location for seismic acquisition and save money by reducing errors that may occur from trying to acquire seismic data in a bad location. [4]

University Research Purposes

At the University of Oklahoma, Geoscience students use LiDAR in many applications. One way is simply to have the opportunity to analyze the outcrop from the comfort of your office for later research. The LiDAR system at OU is capable of producing an image down to the millimeter scale. Reflectors are first placed on the outcrop to give a precise point for stitching the separate images together, then multiple scans are taken in order to capture the entire outcrop. Once completed, the images gathered from the scans are then stitched together using the reflectors to create one large image that will look similar to a panoramic photo, but with much greater resolution (see Figure 3). After completing detailed outcrop analysis in the field, the LiDAR image is another way to view what you were looking at but without having to drive back to the field which may be many hours away. The detail of the LiDAR will pick up many things that may not be noticed when looking at the outcrop with the naked eye. It is a great tool for stratigraphic interpretation and picking out sequence stratigraphies as well as structural interpretation with the mapping of faults, folds and fractures. If seismic data is available for the area that the LiDAR image was collected, this is a way to trace the Geology into the subsurface and correlate LiDAR to seismic. [5]

[5]Figure 3 LiDAR outcrop image collected by Travis Moreland of the University of Oklahoma of the Rader Debris flow in the Delaware Basin. Here you can see the great resolution that the LiDAR scan provides making it ideal for "in the office" analyzing.

Determining Lithologies

[5]Figure 4 LiDAR Reflectance image showing how adding a reflectance layer to a LiDAR image can help in differentiating lithologies.

Another application is adding a reflectance layer to the LiDAR image. Some of the research done at OU has indicated that lithology and changing depositional conditions can be determined from a LiDAR scan when reflectance is applied. The layered turbidites, top left of figure 4 and the mega breccia, bottom right have relatively the same reflectance which is higher than that of the hummocky bed, which is the yellow layer in the middle. The yellow layer was related to higher amounts of silica within the matrix, which absorbs more light thus having a lower reflectance. This has been cross-checked with XRF (X-ray fluorescence) data, which tells the minerals in a rock, to be proven accurate. (see Figure 4) [5]

Other Geoscience Applications

Knowing that LiDAR can map terrain even through vegetation, made it possible for airborne LiDAR surveys to fly over the Seattle area and find the exact location of the Seattle Fault. This is helpful in mitigating earthquake hazards and making sure that future structures are not built on top of the fault. [6]

It can also be used for monitoring the uplift in an area by doing multiple scans of an area year after year and comparing the results. LiDAR was used for this at Mt. St Helens to show the amount of uplift by comparing the data gathered before and after 2004. [7] Slump and erosion can also be monitored by using the same technique. Potential landslide areas can be flagged and monitored and erosion rates can be calculated from yearly scans.

Non-Geoscience Applications

Two popular uses for LiDAR outside of Geosciences are in the agricultural and automotive industries.

Agriculture

[8] Figure 5 Sunlight exposure map of a farmers land showing areas with more intense sunlight than others.

In the Agricultural industry, a farmer can have an airborne LiDAR survey done on his/her land to create a 3D elevation map. This map can then have attributes added on to it in order to show things like the areas on the property that are receiving too much sun (see Figure 5) and not enough water or fertilizer. This will enable the farmer to be able to add more water and fertilizer to the areas that really need it and save money by not adding it to the areas that do not. [8]

Automotive

[8] Figure 6 A new autonomous Lexus with a LiDAR scanner mounted to the roof in order to keep the car driving safely on the road.

Today, there still are not plentiful amounts of self-driving cars out on the roads, but those that are most likely have a LiDAR machine somewhere attached to them (see Figure 6). The LiDAR is able to scan quickly in all directions and see everything around it, and know exactly how far away any objects are from them. This enables them to effectively drive on difficult roads and roads populated by other drivers. [8]

See Also

External Links

References

  1. Bortell, B. (2018). Timmons Group. Retrieved from http://www.timmons.com/what/land-surveying/3d-laser-scanning/
  2. Nayegandhi, Amar. (2014, Feb 28). What is Lidar?. Retrieved from https://www.youtube.com/watch?v=eBUCGxZq_xg/about/Dewberry
  3. 3.0 3.1 Sander, L & S. (2018). Sander Geophysics. Retrieved from http://www.sgl.com/ScanningLiDAR.html
  4. Sfara, R & Wagaman, M. (2005). Applications of LiDAR in seismic acquisition and processing. Evolving Geophysics Through Innovation. 409-412. Retrieved from https://cseg.ca/assets/files/resources/abstracts/2005/078S131-Wagaman_M_Applications_of_LiDAR.pdf
  5. 5.0 5.1 5.2 5.3 Moreland, T & Renner, J. (2018) Digital Grain Size Analysis. Norman, OK: University of Oklahoma.
  6. Paulson, T. (2001,Apr 17).LiDAR Shows Where Earthquake Risks are Highest. Retrieved from https://www.seattlepi.com/local/article/LIDAR-shows-where-earthquake-risks-are-highest-1052381.php
  7. Hewett, J.(2004, Nov, 08).LIDAR studies Mt St Helens uplift.Retrieved from http://optics.org/article/20802
  8. 8.0 8.1 8.2 8.3 Geospatial World. (2017, Dec, 15). What are the Top 5 uses of Lidar? Why is Lidar so important?. Retrieved from https://www.youtube.com/watch?v=zREAEdXzOcw