Close Shot Photogrammetry for Measuring Wind-Drifted Snow Distribution on Stepped Flat Roofs

Yan, Keqin; Cheng, Tao

doi:10.1109/cccm.2008.273

Cited by 3 publications

(3 citation statements)

References 7 publications

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“…A technique that has received considerable attention in recent years is to measure the elevation of the snow surface by airborne or groundbased lidar and subtract from this the snow-free surface elevation, with the difference interpreted as snow depth (Deems et al, 2013;Fassnacht and Deems, 2006;Hopkinson et al, 2004;Prokop, 2008). Operating on the similar principles of repeat or overlapping coverage, but pre-dating lidar studies by 30 years, photogrammetry has also been used to produce snow depth maps (Cline, 1994;König and Sturm, 1998;Lee et al, 2008;McKay, 1968;Najibi and Arabsheibani, 2013;Otake, 1980;Rawls et al, 1980;Yan and Cheng, 2008), including using stereo-imagery from opto-electronic linescanners incorporating near-IR wavelengths in addition to RGB (Bühler et al, 2014;Buhler et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Mapping snow depth from manned aircraft on landscape scales at centimeter resolution using structure-from-motion photogrammetry

2015

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Abstract. Airborne photogrammetry is undergoing a renaissance: lower-cost equipment, more powerful software, and simplified methods have significantly lowered the barriers to entry and now allow repeat mapping of cryospheric dynamics at spatial resolutions and temporal frequencies that were previously too expensive to consider. Here we apply these advancements to the measurement of snow depth from manned aircraft. Our main airborne hardware consists of a consumer-grade digital camera directly coupled to a dual-frequency GPS; no inertial motion unit (IMU) or on-board computer is required, such that system hardware and software costs less than USD 30 000, exclusive of aircraft. The photogrammetric processing is done using a commercially available implementation of the structure from motion (SfM) algorithm. The system is simple enough that it can be operated by the pilot without additional assistance and the technique creates directly georeferenced maps without ground control, further reducing overall costs. To map snow depth, we made digital elevation models (DEMs) during snow-free and snow-covered conditions, then subtracted these to create difference DEMs (dDEMs). We assessed the accuracy (real-world geolocation) and precision (repeatability) of our DEMs through comparisons to ground control points and to time series of our own DEMs. We validated these assessments through comparisons to DEMs made by airborne lidar and by a similar photogrammetric system. We empirically determined that our DEMs have a geolocation accuracy of ±30 cm and a repeatability of ±8 cm (both 95 % confidence). We then validated our dDEMs against more than 6000 hand-probed snow depth measurements at 3 separate test areas in Alaska covering a wide-variety of terrain and snow types. These areas ranged from 5 to 40 km2 and had ground sample distances of 6 to 20 cm. We found that depths produced from the dDEMs matched probe depths with a 10 cm standard deviation, and were statistically identical at 95 % confidence. Due to the precision of this technique, other real changes on the ground such as frost heave, vegetative compaction by snow, and even footprints become sources of error in the measurement of thin snow packs (< 20 cm). The ability to directly measure such small changes over entire landscapes eliminates the need to extrapolate limited field measurements. The fact that this mapping can be done at substantially lower costs than current methods may transform the way we approach studying change in the cryosphere.

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Section: Introductionmentioning

confidence: 99%

Mapping snow depth from manned aircraft on landscape scales at centimeter resolution using structure-from-motion photogrammetry

2015

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Section: Introductionmentioning

confidence: 99%

Mapping snow-depth from manned-aircraft on landscape scales at centimeter resolution using Structure-from-Motion photogrammetry

Nolan¹,

Larsen²,

Sturm³

2015

Preprint

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Abstract. Airborne photogrammetry is undergoing a renaissance: lower-cost equipment, more powerful software, and simplified methods have significantly lowered the barriers-to-entry and now allow repeat-mapping of cryospheric dynamics at spatial resolutions and temporal frequencies that were previously too expensive to consider. Here we apply these techniques to the measurement of snow depth from manned aircraft. The main airborne hardware consists of a consumer-grade digital camera coupled to a dual-frequency GPS. The photogrammetric processing is done using a commercially-available implementation of the Structure from Motion (SfM) algorithm. The system hardware and software, exclusive of aircraft, costs less than USD 30 000. The technique creates directly-georeferenced maps without ground control, further reducing costs. To map snow depth, we made digital elevation models (DEMs) during snow-free and snow-covered conditions, then subtracted these to create difference DEMs (dDEMs). We assessed the accuracy (geolocation) and precision (repeatability) of our DEMs through comparisons to ground control points and to time-series of our own DEMs. We validated these assessments through comparisons to DEMs made by airborne lidar and by another photogrammetric system. We empirically determined an accuracy of ± 30 cm and a precision of ± 8 cm (both 95% confidence) for our methods. We then validated our dDEMs against more than 6000 hand-probed snow depth measurements at 3 test areas in Alaska covering a wide-variety of terrain and snow types. These areas ranged from 5 to 40 km2 and had ground sample distances of 6 to 20 cm. We found that depths produced from the dDEMs matched probe depths with a 10 cm standard deviation, and these depth distributions were statistically identical at 95% confidence. Due to the precision of this technique, other real changes on the ground such as frost heave, vegetative compaction by snow, and even footprints become sources of error in the measurement of thin snow packs (< 20 cm). The ability to directly measure such small changes over entire landscapes eliminates the need to extrapolate isolated field measurements. The fact that this mapping can be done at substantially lower costs than current methods may transform the way we approach studying change in the cryosphere.

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“…The basic process is that arrange some observation dots first and then measure the snow depth by ruler at these points, finally to get the regularity of snow distribution on the roof by statistic data. To keep snow original state and improve the efficient, close shot photogrammetry which used by Keqin Yan [5] is adopted to gain the snow distribution on the roofs. The method is by taking photos on observation points and then through digital image process to get the condition of snow distribution.…”

Section: The Measurement and Simulation Of Snow Accumulation On The R...mentioning

confidence: 99%

Snow Distribution on Low-Rise Roofs and Practical Analysis Method

Meng

et al. 2013

AMR

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Snow related failures can have significant impact on the safety of people who occupy snow damaged buildings. So the research for snow distribution characteristics on the roofs can avoid personnel casualty and economic losses caused by heavy snowdrift. This paper outlines the current researches of snow distribution on surface of the different roofs and the methods of researching for snowdrifting. The practical calculation method of the snow load on the typical low rise buildings was investigated by comparison between the different countries load code for example China, America, Canada and Europe.

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Close Shot Photogrammetry for Measuring Wind-Drifted Snow Distribution on Stepped Flat Roofs

Cited by 3 publications

References 7 publications

Mapping snow depth from manned aircraft on landscape scales at centimeter resolution using structure-from-motion photogrammetry

Mapping snow depth from manned aircraft on landscape scales at centimeter resolution using structure-from-motion photogrammetry

Mapping snow-depth from manned-aircraft on landscape scales at centimeter resolution using Structure-from-Motion photogrammetry

Snow Distribution on Low-Rise Roofs and Practical Analysis Method

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