LiDAR: What and Why?

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● LiDAR: What and Why?
● LiDAR: How?
● Traditional Photogrammetry vs. LiDAR
● Intensity Image
● Aerial LiDAR System Components*
● Scanning Mechanisms
● Determinants of LiDAR Data Characteristic
● LiDAR Data Characteristics
● Return Density
● Reflectivity
● Dust & Vapor
● Background Noise and Radiation
● Overall Accuracy
● Data Ordering Details
● Leaf-on vs. leaf-off
● What are some of the LIDAR data products available?
● Sources of Error
● Acquisition Scan Angle
● Strip Adjustment
● Selecting Ground Points
● Getting Down to the Ground
● Filtering
● Terrain
● Interpolation
● Example: Mapping forest attributes across landscapes
● Other Considerations
● Visualization
● Further Analysis & Ground Validation

نوع زبان: انگلیسی حجم: 9.27 مگا بایت
نوع فایل: اسلاید پاورپوینت تعداد اسلایدها: 35 صفحه
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گروه موضوعی: زمان استخراج مطلب: 2019/05/16 06:16:31

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عبارات مهم استفاده شده در این مطلب

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lidar, datum, ., return, pulse, laser, system, image, time, flight, acquisition, hectare,

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عبارات پرتکرار و مهم در این اسلاید عبارتند از: lidar, datum, ., return, pulse, laser, system, image, time, flight, acquisition, hectare,

مشاهده محتوای متنیِ این اسلاید ppt

مشاهده محتوای متنیِ این اسلاید ppt

lidar fundamentals part one l. monika moskal phd assistant professor remote sensing biospatial analysis college of forest resources precision forestry cooperative university of washington workshop on site scale applications of lidar on forest lands in washington center for urban horticulture uw thursday january ۳ ۲ ۸ lidar what and why lidar stands for light detection and ranging commonly known as laser radar lidar is not only replacing conventional sensors but also creating new methods with unique properties that could not be achieved before discrete lidar lidar how each time the laser is pulsed laser generates an optical pulse pulse is reflected off an object and returns to the system receiver high speed counter measures the time of flight from the start pulse to the return pulse time measurement is converted to a distance the distance to the target and the position of the airplane is then used to determine the elevation and location multiple returns can be measured for each pulse up to ۲ pulses second everything that can be seen from the aircraft is measured traditional photogrammetry vs. lidar complementary characteristics suggest integration lidar photogrammetric day or night data acquisition day time collection only direct acquisition of ۳d collection complicated and sometimes unreliable procedures vertical accuracy is better than planimetric planimetric accuracy is better than vertical point cloud difficult to derive semantic information however intensity values can be used to produce a visually rich image like product example of an intensity image rich in semantic information intensity image commonly unused bi product of a lidar acquisition and is the intensity of object that the laser pulse is striking. this is an uncalibrated ۸ bit ۲۵۵ image that is ortho rectified as therefore can be used as an orthophoto not typically used in quantitative analysis as image gains always set to adaptive gain setting when images are acquired aerial lidar system components aircraft scanning laser emitter receiver unit differentially corrected gps inertial measurement unit imu computer figures from mcmcgaughey usda forest service pnw research station lidar point data colored by height components can be sources of error…more on this in part ii scanning mechanisms figure modified from nikolaos ۲ ۶ mechanism ground pattern most common pattern leica optech sawtooth determinants of lidar data characteristic the combination of scanner system relates to beam pattern flight altitude if flight limitations exist pulse rates scan frequencies scan angle possible max around ۳ ° scan swath lidar data characteristics raw return data are xyz points high spatial resolution laser footprint on ground ≤ .۵ meters typical density is .۵ to ۲ pulses m۲ ۲ to۳ returns pulse in forest areas surface canopy models typically ۱ to ۵m grid large volume of data ۵ to ۶ pulses hectare ۱ to۱ thousands of returns hectare .۴ to ۵.۴ mb hectare the low number correspond to lidar collected for topographic mapping applications the high numbers correspond to lidar collected for vegetation characterization return density in lidar the footprint size decreases with increasing post spacing and importantly the last return from a discrete return system is not always the ground lidar sensor systems vary in the number of returns from a surface figure source http reflectivity highly reflective objects may saturate some laser detectors while the return signal from low reflectivity objects may occasionally be too weak to register as valid minimum detectable object size depends on reflectivity a strong sunlight reflection off a highly reflective target may saturate a receiver producing an invalid or less accurate reading most acquisition is done in a preferred range of angles to avoid this issue dust vapor laser measurements can be weakened by interacting with dust and vapor particles which scatter the laser beam and the signal returning from the target using last pulse measurements can reduce or eliminate this interference systems that are expected to work in such conditions regularly can be optimized for these environments background noise and radiation the laser is not affected by background noise most systems determine baseline radiation levels to ensure that it does not interfere with measurements overall accuracy x y z position of each return ۵ ۱ cm horizontal ۱ ۱۵cm vertical ground surface bare earth surface what is the ground grass rocks stumps tree heights underestimate tree heights by .۵ to ۲ m error is species dependent lidar dem canopy models ifsar ifsar ۱ m usgs dem lidar guest lecturer dr. l. monika moskal uw spring ۲ ۷ esrm۴۹ h streams landslide data ordering details data acquisition there are a number of private companies academic institutions and government agencies that produce and provide lidar data. timing there are a number of time constraints associated with lidar collection and delivery flight schedules can be delayed due to weather and environmental factors project areas may be large enough that multiple flights are needed post processing of millions of raw data points can be time consuming producing additional deliverables can delay the delivery schedule leaf on or leaf off example costs cost can vary depending on size of project horizontal postings point density and project location. cost may also increase based on additional product requests i.e. dems dtms contours etc. specific accuracy requirements or licensing restrictions. most current estimated lidar ۱ ۴ hectare ۱ hectare ~۲.۵ acres ۶۴ acres ۱mi۲ aerial photography pennies hectare slight difference in cost for non stereo vs. stereo formats common lidar data exchange format .las industry initiative asprs . the las file format is a public file format for the interchange of lidar data between vendors and customers. this binary file format is an alternative to proprietary systems or a generic ascii file interchange system used by many companies. know understand the flight acquisition parameters always get the raw data it can be reprocessed later with newer techniques algorithms get an intensity image projections lidar data can be delivered in many different projections and datums. the national standard for vertical datum is the north american vertical datum navd ۸۸ and the national standard for horizontal datum is the north american datum of ۱۹۸۳ nad ۸۳ . licensing licensing restrictions vary for each lidar service provider. many providers do not have restrictions on their data products but some companies do require licensing. leaf on vs. leaf off cross section of lidar data through a single deciduous …

کلمات کلیدی پرکاربرد در این اسلاید پاورپوینت: lidar, datum, ., return, pulse, laser, system, image, time, flight, acquisition, hectare,

این فایل پاورپوینت شامل 35 اسلاید و به زبان انگلیسی و حجم آن 9.27 مگا بایت است. نوع قالب فایل ppt بوده که با این لینک قابل دانلود است. این مطلب برگرفته از سایت زیر است و مسئولیت انتشار آن با منبع اصلی می باشد که در تاریخ 2019/05/16 06:16:31 استخراج شده است.

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