How Does LiDAR Remote Sensing Work? Light Detection and Ranging 

Glad it was useful!

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Torrie - I'm so glad the video was useful for you.

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Chuck -- thank you for the kind words. We agree -- videos like these are important to helping people understand these technologies and the wide variety of sciences that remote sensing and lidar underpin. Glad to hear that it is useful to you. We are regularly adding move videos to the NEONScience channel. Not all will be remote sensing/lidar focused but they may still be of interest to you.

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I am a layman, but LIDAR has helped define the route of a Roman road near my home. It is amazing technology and as a geographer it is brilliant in revealing morphology of the landscape which is virtually imperceptible to the human eye. Power to you!

Excellent! We're glad it is useful.

Thank you! Glad you found it useful.

Thank you! Glad you found it useful.

+Amanuel Beyin we are glad that you enjoyed the video! thank you for the positive feedback!

no, she's sexy. Come on bro

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Glad you found the video useful! Go Emus!!!

Glad you found it useful.

+uday sen pendiala Thank you - we are glad you enjoyed it!

I'm so glad you found this video useful! It is nice to have a short visual when explaining our research!

Glad you found it useful. Hope you do great on the exam!

of course! we are glad that you enjoyed it!

+Tùng Lâm Nguyễn Glad you enjoyed the video! thank you for the feedback!

+Marcos Spinelli glad you enjoyed it!

Thanks for the feedback. Glad it helped.

Feel free to share with other students! Glad you found it useful.

You 're welcome. Glad the information was useful.

PDF Book: Image Processing & GIS for Remote Sensing: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-EkwiJg0RYCA.html

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Awe I liked the bird

I agree, pretty cringy

info was good presentation like for 2nd graders not so much

IMU! URMI ? NO IMMI. So URU ! Yes! But we are taking about IMU.

I’m five yrs late to the party, however the equations were an equal match.

Thank you for the feedback. Glad you found the information useful!

Thanks. Glad you found it useful.

@mr.1n5an_e dang shame you are a Mr. ;-)

Thank you for adding the excellent point of clarification. We did simply the graphic to just show the points of intersection on a circle, not the sphere.

Eddie Aiello Hi Eddie! we are glad you enjoyed the video! there are a lot of great resources out there to learn more. For instance, in the past year Penn State has put many of their course materials online! www.worldcampus.psu.edu/RS so you can read through their materials. they have an entire section on lidar as well in there and some other courses in imagery. i'd start there!:) another older tutorial was produced by NASA years ago. I found a copy of it here www.fas.org/irp/imint/docs/rst/Front/tofc.html ... the formatting visually is a bit dated by the information is solid and provides a good general foundation. i'm sure there are others as well but these two have a lot of content to go through that you might enjoy! Cheers!

Thank you so much for all the great info! I can't wait for some more great videos from you...

Interesting question! LiDAR can be used to detect fires but the detection is actually based on the smoke, not the flame (see reference here: journals.sagepub.com/doi/full/10.1155/2014/597368). The laser needs an object to bounce back from.

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Hi. There are many different ways to estimate the structure of a forest. Are you interested in heterogeneity of tree heights, the biomass of trees in a given area, layers of canopy, etc. We don't have a video specifically about these topics. However, we do offer some tutorials for calculating some of the parameters that go into these questions on our website: www.neonscience.org/resources/data-tutorials

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Good point! Also I have a question - how does it always return emitted laser pulse back to the plane? - How can we guarantee the needed angle? What if the surface just reflects it to another direction?

you're right each pulse has a carrier phase signature associated with it, no clock can measure such a fast return but it can record when the individual pulse leaves and then later calculate when that distinct pulse returned

Thanks!

+Atharva Deshpande thank you - we are glad you enjoyed the video

Thank you.

Pranav Hirave hi there!! we are glad you enjoyed the video! good question. there are lidar data available for various parts of the world however you'd have to search in that region to figure out if data have been flown for the areas your interested in. It's can be pricey to collect so larger collections are a bit more rare in many parts of the world. Lidar has been used to identify conifer vs deciduous over larger areas. But it's more effective if you combine lidar with imagery to get into species mapping. lots of options however! thank you for your comment and good luck with your project!! :)

Yeah thanks to you too..! I would definitely search for such data repository

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Anurag Dixt - great question. And yes, if the ground was utterly, perfectly flat that is true. However, given that all objects are less than ideally smooth when the laser hits the ground the light scatters and some of it does bounce back at the receivers.

+Praveen Singh Hi Praveen - We use Adobe After effects mostly! Although we record using audition.

Agreed. There has definitely been a shift over the last 5 or so years.

What’s that?

Thank you! Glad you found it useful.

Hi. Unfortunately, I'm not sure which "forest structure" video you are referring to. All of our animated science videos can be found in this playlist: ru-vid.com/group/PLLWiknuNGd50GI8OZf3EBo6PMx04xcoFa

Honestly this had more information than any of the so-called lectures I've looked at. Those all took 15 minutes to be like "and radar uses radio" ok dude great. At least this mentioned the IMU, and some of the subtlety of difficulties in measuring, and talked about how the measurement is made (maybe you missed it judging from your "summary" there). This channel I think is for general audiences so it's actually pretty impressive they got through so much while some person meant to give an hour long lecture can't even get around to wavelength choice or location and movement considerations.

Ευχαριστώ

+D Bay This is a fantastic question. We consulted with NEON Airborne Observation Platform Staff Scientists on this question! Here is your answer - the lidar does not need an atomic clock - please read below. ``````````````````````` Great question! Yes, the time between transmission and reception is incredibly small. We do not require an atomic clock, those are in GPS satellites and are required for very accurate and precise absolute time. We do not need absolute time in the LIDAR systems, only relative time (the time it takes for the pulse to travel to the ground and back). Calculating this time can be achieved with less expensive solutions than atomic clocks. The clocks in the waveform digitizers for both the Riegl and Optech sensors (the ones we are using) are capable of measuring to a precision of 1 nano second. Given a pulse travels ~0.15 m in a nano second, this is sufficient resolution to accurately measure travel time and in turn calculate distance. ```````````` We hope that this answers your question!

GPS time or UTM and is atomic. Yes the time is incredibly small but can be measured all the same. A technology called DGPS is already being used to measure positions to 1m accuracy and even less if need be. The question to ask though is the possible smearing of the data since the plane is not stationary. That is the place will have moved some distance before the reflected light returns. But again this may be insignificant compared to the speed of light and for small elevations.

NEON Associate Scientist Tristan Goulden offers these comments on your questions: The ‘resolution’ of LiDAR can vary depending on the type of sensor and platform. Typically airborne LiDAR surveys with fixed wing aircraft can normally achieve 5 - 10 points per square meter with the most recent sensors. Using a helicopter, the point density can be increased due to the ability to fly at lower altitudes and speeds, however this comes at an increased cost. Using a helicopter point densities up to 50 points per square meter are not uncommon. The most dense LiDAR surveys can be acquired through terrestrial laser scanners. These are stationary systems that scan from the ground. The point density from these systems can be as high as the user desires, typically achieving hundreds of points per square meter. However, it takes much longer to cover a large area than an airborne survey. Raw LiDAR data is termed a ‘point cloud’, and point density is often used as a metric as opposed to resolution. Once the LiDAR point cloud is ‘gridded’ into a raster product such as a DTM or DEM, resolution is a more common term. LiDAR rasters are typically created at twice the nominal point density. For example, if your point cloud achieves two points per square meter, you should only create a raster product with a resolution of 1 meter. Yes, LiDAR is a good technology to map a boulder train of that size with an airborne survey or terrestrial survey being options. A terrestrial laser scanner will take a lot of time for an area that size, however may be cheaper. An airborne survey of the area that size would be quick, but incurs significant overhead in deploying an aircraft so costs come down significantly as the size of the area increases. Exact costs are highly dependent on the area, type of sensor and aircraft desired, or time required for a terrestrial scan. There are several remote sensing and land surveying companies that will provide these services for private parties and would be able to provide reliable costs estimates. -- NEON's Assignable Assets program (www.neonscience.org/assignable-assets) will include airborne LiDAR capabilities.

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Thank you!