Evaluation of SfM for surface characterization of a snow-covered glacier through comparison with aerial lidar

The combined use of unmanned aerial vehicles (UAVs) and structure-from-motion (SfM) is rapidly growing as a cost-effective alternative to airborne laser scanning (lidar) for reconstructing glacier surfaces. Here we present a thorough analysis of the precision and accuracy of a photogrammetric point cloud (PPC) constructed through SfM from UAV-acquired imagery over the spring snow surface at Haig Glacier, Alberta, Canada, the first of its kind in a glaciological setting. An aerial lidar survey conducted concurrently with UAV surveys was used to examine spatial patterns in the PPC accuracy. We found a median error in the PPC of −0.046 ± 0.067 m, with a 95% quantile of 0.218 m. Mean precision of the PPC was 0.199 m, with large spatially clustered outliers. We found an association between high-error, low-precision, and high-surface roughness in the PPC, likely due to illumination characteristics of the snow surface. Glacier surface reconstructions are important for geodetic mass balance measurements, giving key insights into changing climate where in situ measurements are difficult to obtain. The PPC errors are small enough that they would have minimal effects on total mass balance, should the technique be applied across the glacier.

Download Full-text

Geodetic Mass Balance of Haxilegen Glacier No. 51, Eastern Tien Shan, from 1964 to 2018

Remote Sensing ◽

10.3390/rs14020272 ◽

2022 ◽

Vol 14 (2) ◽

pp. 272

Author(s):

Chunhai Xu ◽

Zhongqin Li ◽

Feiteng Wang ◽

Jianxin Mu ◽

Xin Zhang

Keyword(s):

Mass Loss ◽

Mass Balance ◽

Laser Scanning ◽

Mean Value ◽

Tien Shan ◽

Glacier Mass Balance ◽

Topographic Map ◽

Glacier Surface ◽

Elevation Changes ◽

Geodetic Mass Balance

The eastern Tien Shan hosts substantial mid-latitude glaciers, but in situ glacier mass balance records are extremely sparse. Haxilegen Glacier No. 51 (eastern Tien Shan, China) is one of the very few well-measured glaciers, and comprehensive glaciological measurements were implemented from 1999 to 2011 and re-established in 2017. Mass balance of Haxilegen Glacier No. 51 (1999–2015) has recently been reported, but the mass balance record has not extended to the period before 1999. Here, we used a 1:50,000-scale topographic map and long-range terrestrial laser scanning (TLS) data to calculate the area, volume, and mass changes for Haxilegen Glacier No. 51 from 1964 to 2018. Haxilegen Glacier No. 51 lost 0.34 km2 (at a rate of 0.006 km2 a−1 or 0.42% a−1) of its area during the period 1964–2018. The glacier experienced clearly negative surface elevation changes and geodetic mass balance. Thinning occurred almost across the entire glacier surface, with a mean value of −0.43 ± 0.12 m a−1. The calculated average geodetic mass balance was −0.36 ± 0.12 m w.e. a−1. Without considering the error bounds of mass balance estimates, glacier mass loss over the past 50 years was in line with the observed and modeled mass balance (−0.37 ± 0.22 m w.e. a−1) that was published for short time intervals since 1999 but was slightly less negative than glacier mass loss in the entire eastern Tien Shan. Our results indicate that Riegl VZ®-6000 TLS can be widely used for mass balance measurements of unmonitored individual glaciers.

Download Full-text

Investigations on intra-annual elevation changes using multi-temporal airborne laser scanning data: case study Engabreen, Norway

Annals of Glaciology ◽

10.3189/172756405781812592 ◽

2005 ◽

Vol 42 ◽

pp. 195-201 ◽

Cited By ~ 34

Author(s):

Thomas Geist ◽

Hallgeir Elvehøy ◽

Miriam Jackson ◽

Johann Stötter

Keyword(s):

Mass Balance ◽

Laser Scanning ◽

Laser Scanner ◽

Remote Sensing Data ◽

Control Area ◽

Airborne Laser Scanning ◽

Time Interval ◽

Scanner Data ◽

Glacier Surface ◽

Airborne Laser

AbstractKey issues of glacier monitoring are changes in glacier geometry and glacier mass. As accurate direct measurements are costly and time-consuming, the use of various remote-sensing data for glacier monitoring is explored. One technology used and described here is airborne laser scanning. The method enables the derivation of high-quality digital elevation models (DEMs) with a vertical and horizontal accuracy in the sub-metre range. Between September 2001 and August 2002, three laser scanner data acquisition flights were carried out, covering the whole area of Engabreen, Norway, and corresponding well to the measurement dates for the mass-balance year 2001/02. The data quality of the DEMs is assessed (e.g. by comparing the values with a control area which has been surveyed independently or GPS ground profiles measured during the flights). For the whole glacier, surface elevation change and consequently volume change is calculated, quantified and compared with traditional mass-balance data for the same time interval. For the winter term, emergence/submergence velocity is determined from laser scanner data and snow-depth data and is compared with velocity measurements at stakes. The investigations reveal the high potential of airborne laser scanning for measuring the extent and the topography of glaciers as well as changes in geometry (Δarea, Δvolume).

Download Full-text

Minor Imbalance of the Lowermost Italian Glacier from 2006 to 2019

Water ◽

10.3390/w12092503 ◽

2020 ◽

Vol 12 (9) ◽

pp. 2503

Author(s):

Jessica De Marco ◽

Luca Carturan ◽

Livia Piermattei ◽

Sara Cucchiaro ◽

Daniele Moro ◽

...

Keyword(s):

Mass Balance ◽

Laser Scanning ◽

Climate Changes ◽

Average Rate ◽

European Alps ◽

Surface Dynamics ◽

Solid Precipitation ◽

Airborne Laser ◽

Geodetic Mass Balance ◽

Annual Balance

The response of very small glaciers to climate changes is highly scattered and little known in comparison with larger ice bodies. In particular, small avalanche-fed and debris-covered glaciers lack mass balance series of sufficient length. In this paper we present 13 years of high-resolution observations over the Occidentale del Montasio Glacier, collected using Airborne Laser Scanning, Terrestrial Laser Scanning, and Structure from Motion Multi-View Stereo techniques for monitoring its geodetic mass balance and surface dynamics. The results have been analyzed jointly with meteorological variables, and compared to a sample of “reference” glaciers for the European Alps. From 2006 to 2019 the mass balance showed high interannual variability and an average rate much closer to zero than the average of the Alpine reference glaciers (−0.09 vs. −1.42 m water equivalent per year, respectively). This behavior can be explained by the high correlation between annual balance and solid precipitation, which displayed recent peaks. The air temperature is not significantly correlated with the mass balance, which is main controlled by avalanche activity, shadowing and debris cover. However, its rapid increase is progressively reducing the fraction of solid precipitation, and increasing the length of the ablation season.

Download Full-text

Latest Geodetic Changes of Austre Lovénbreen and Pedersenbreen, Svalbard

Remote Sensing ◽

10.3390/rs11242890 ◽

2019 ◽

Vol 11 (24) ◽

pp. 2890 ◽

Cited By ~ 1

Author(s):

Songtao Ai ◽

Xi Ding ◽

Florian Tolle ◽

Zemin Wang ◽

Xi Zhao

Keyword(s):

Mass Balance ◽

Snow Depth ◽

Spline Interpolation ◽

Time Interval ◽

Short Time Interval ◽

Mass Balances ◽

Glacier Surface ◽

Elevation Changes ◽

Rtk Gps ◽

Geodetic Mass Balance

Geodetic mass changes in the Svalbard glaciers Austre Lovénbreen and Pedersenbreen were studied via high-precision real-time kinematic (RTK)-global positioning system (GPS) measurements from 2013 to 2015. To evaluate the elevation changes of the two Svalbard glaciers, more than 10,000 GPS records for each glacier surface were collected every year from 2013 to 2015. The results of several widely used interpolation methods (i.e., inverse distance weighting (IDW), ordinary kriging (OK), universal kriging (UK), natural neighbor (NN), spline interpolation, and Topo to Raster (TTR) interpolation) were compared. Considering the smoothness and accuracy of the glacier surface, NN interpolation was selected as the most suitable interpolation method to generate a surface digital elevation model (DEM). In addition, we compared two procedures for calculating elevation changes: using DEMs generated from the direct interpolation of the RTK-GPS points and using the elevation bias of crossover points from the RTK-GPS tracks in different years. Then, the geodetic mass balances were calculated by converting the elevation changes to their water equivalents. Comparing the geodetic mass balances calculated with and without considering snow depth revealed that ignoring the effect of snow depth, which differs greatly over a short time interval, might lead to bias in mass balance investigation. In summary, there was a positive correlation between the geodetic mass balance and the corresponding elevation. The mass loss increased with decreasing elevation, and the mean annual gradients of the geodetic mass balance along the elevation of Austre Lovénbreen and Pedersenbreen in 2013–2015 were approximately 2.60‰ and 2.35‰, respectively. The gradients at the glacier snouts were three times larger than those over the whole glaciers. Additionally, some mass gain occurred in certain high-elevation regions. Compared with a 2019 DEM generated from unmanned aerial vehicle measurement, the glacier snout areas presented an accelerating thinning situation in 2015–2019.

Download Full-text

Comparison of direct and geodetic mass balances on an annual time scale

The Cryosphere Discussions ◽

10.5194/tcd-5-565-2011 ◽

2011 ◽

Vol 5 (1) ◽

pp. 565-604 ◽

Cited By ~ 4

Author(s):

A. Fischer ◽

H. Schneider ◽

G. Merkel ◽

R. Sailer

Keyword(s):

Mass Balance ◽

Flow Velocity ◽

Volume Change ◽

Glacier Surface ◽

Ice Flow ◽

Total Period ◽

Elevation Data ◽

Order Of Magnitude ◽

The Difference ◽

Geodetic Mass Balance

Abstract. Very accurate airborne laserscanning (ALS) elevation data was used to calculate the annual volume changes for Hintereisferner and Kesselwandferner in the Ötztal Alps, Austria for 2001/2002–2008/2009. The comparison of the altitude of 51 recently GPS surveyed ground control points showed that the accuracy of the ALS DEMs is better than 0.3 m. The geodetic mass balance was calculated from the volume change using detailed maps of the firn cover and applying corrections for the seasonal snow cover. The maximum snow height at the time of the elevation data flight was 0.5 m averaged over the glacier surface. The volume change data was compared to in situ mass balance data for the total area and at the stakes. For the total period of 8 yr, the difference between the geodetic and the direct mass balance is 2.398 m w.e. on Hintereisferner and 1.380 m w.e. on Kesselwandferner, corresponding to about two times the mean annual mass balance. The vertical ice flow velocity was measured and found to be on the same order of magnitude as the mass balance at KWF. This is an indicator that volume change data does not allow the calculation of ablation or accumulation rates without detailed measurements or models of the vertical ice flow velocity. Therefore, only direct mass balance data allow process studies or investigation of the climatic controls of the resulting mass changes.

Download Full-text

Comparison of direct and geodetic mass balances on a multi-annual time scale

The Cryosphere ◽

10.5194/tc-5-107-2011 ◽

2011 ◽

Vol 5 (1) ◽

pp. 107-124 ◽

Cited By ~ 65

Author(s):

A. Fischer

Keyword(s):

Mass Balance ◽

Laser Scanning ◽

Climate Forcing ◽

Mass Balances ◽

Scanning Lidar ◽

Cumulative Difference ◽

The Mean ◽

The Difference ◽

Geodetic Mass Balance ◽

Seasonal Snow Cover

Abstract. The geodetic mass balances of six Austrian glaciers over 19 periods between 1953 and 2006 are compared to the direct mass balances over the same periods. For two glaciers, Hintereisferner and Kesselwandferner, case studies showing possible reasons for discrepancies between the geodetic and the direct mass balance are presented. The mean annual geodetic mass balance for all periods is −0.5 m w.e. a−1, the mean annual direct mass balance −0.4 m w.e. a−1. The mean cumulative difference is −0.6 m w.e., the minimum −7.3 m w.e., and the maximum 5.6 m w.e. The accuracy of geodetic mass balance may depend on the accuracy of the DEMs, which ranges from 2 m w.e. for photogrammetric data to 0.02 m w.e. for airborne laser scanning (LiDAR) data. Basal melt, seasonal snow cover, and density changes of the surface layer also contribute up to 0.7 m w.e. to the difference between the two methods over the investigated period of 10 yr. On Hintereisferner, the fraction of area covered by snow or firn has been changing within 1953–2006. The accumulation area is not identical with the firn area, and both are not coincident with areas of volume gain. Longer periods between the acquisition of the DEMs do not necessarily result in a higher accuracy of the geodetic mass balance. Trends in the difference between the direct and the geodetic data vary from glacier to glacier and can differ systematically for specific glaciers under specific types of climate forcing. Ultimately, geodetic and direct mass balance data are complementary, and great care must be taken when attempting to combine them.

Download Full-text

Geodetic mass balance record with rigorous uncertainty estimates deduced from aerial photographs and lidar data – Case study from Drangajökull ice cap, NW Iceland

The Cryosphere ◽

10.5194/tc-10-159-2016 ◽

2016 ◽

Vol 10 (1) ◽

pp. 159-177 ◽

Cited By ~ 28

Author(s):

E. Magnússon ◽

J. Muñoz-Cobo Belart ◽

F. Pálsson ◽

H. Ágústsson ◽

P. Crochet

Keyword(s):

High Resolution ◽

Mass Balance ◽

Bias Correction ◽

Aerial Photographs ◽

Glacier Surface ◽

Ice Cap ◽

Uncertainty Estimates ◽

Lidar Dem ◽

Geodetic Mass Balance

Abstract. In this paper we describe how recent high-resolution digital elevation models (DEMs) can be used to extract glacier surface DEMs from old aerial photographs and to evaluate the uncertainty of the mass balance record derived from the DEMs. We present a case study for Drangajökull ice cap, NW Iceland. This ice cap covered an area of 144 km2 when it was surveyed with airborne lidar in 2011. Aerial photographs spanning all or most of the ice cap are available from survey flights in 1946, 1960, 1975, 1985, 1994 and 2005. All ground control points used to constrain the orientation of the aerial photographs were obtained from the high-resolution lidar DEM. The lidar DEM was also used to estimate errors of the extracted photogrammetric DEMs in ice- and snow-free areas, at nunataks and outside the glacier margin. The derived errors of each DEM were used to constrain a spherical semivariogram model, which along with the derived errors in ice- and snow-free areas were used as inputs into 1000 sequential Gaussian simulations (SGSims). The simulations were used to estimate the possible bias in the entire glaciated part of the DEM and the 95 % confidence level of this bias. This results in bias correction varying in magnitude between 0.03 m (in 1975) and 1.66 m (in 1946) and uncertainty values between ±0.21 m (in 2005) and ±1.58 m (in 1946). Error estimation methods based on more simple proxies would typically yield 2–4 times larger error estimates. The aerial photographs used were acquired between late June and early October. An additional seasonal bias correction was therefore estimated using a degree-day model to obtain the volume change between the start of 2 glaciological years (1 October). This correction was largest for the 1960 DEM, corresponding to an average elevation change of −3.5 m or approx. three-quarters of the volume change between the 1960 and the 1975 DEMs. The total uncertainty of the derived mass balance record is dominated by uncertainty in the volume changes caused by uncertainties of the SGSim bias correction, the seasonal bias correction and the interpolation of glacier surface where data are lacking. The record shows a glacier-wide mass balance rate of Ḃ = −0.26 ± 0.04 m w.e. a−1 for the entire study period (1946–2011). We observe significant decadal variability including periods of mass gain, peaking in 1985–1994 with Ḃ = 0.27 ± 0.11 m w.e. a−1. There is a striking difference when Ḃ is calculated separately for the western and eastern halves of Drangajökull, with a reduction of eastern part on average ∼  3 times faster than the western part. Our study emphasizes the need for applying rigorous geostatistical methods for obtaining uncertainty estimates of geodetic mass balance, the importance of seasonal corrections of DEMs from glaciers with high mass turnover and the risk of extrapolating mass balance record from one glacier to another even over short distances.

Download Full-text

Changes in the southeast Vatnajökull ice cap, Iceland, between ~ 1890 and 2010

The Cryosphere ◽

10.5194/tc-9-565-2015 ◽

2015 ◽

Vol 9 (2) ◽

pp. 565-585 ◽

Cited By ~ 32

Author(s):

H. Hannesdóttir ◽

H. Björnsson ◽

F. Pálsson ◽

G. Aðalgeirsdóttir ◽

Sv. Guðmundsson

Keyword(s):

Mass Balance ◽

Aerial Images ◽

Ice Age ◽

Volume Loss ◽

Volume Changes ◽

Glacier Surface ◽

Early 21St Century ◽

Ice Cap ◽

Multi Temporal ◽

Geodetic Mass Balance

Abstract. Area and volume changes and the average geodetic mass balance of the non-surging outlet glaciers of the southeast Vatnajökull ice cap, Iceland, during different time periods between ~ 1890 and 2010, are derived from a multi-temporal glacier inventory. A series of digital elevation models (DEMs) (~ 1890, 1904, 1936, 1945, 1989, 2002, 2010) are compiled from glacial geomorphological features, historical photographs, maps, aerial images, DGPS measurements and a lidar survey. Given the mapped basal topography, we estimate volume changes since the end of the Little Ice Age (LIA) ~ 1890. The variable volume loss of the outlets to similar climate forcing is related to their different hypsometry, basal topography, and the presence of proglacial lakes. In the post-LIA period, the glacierized area decreased by 164 km2 (or from 1014 to 851 km2) and the glaciers had lost 10–30 % of their ~ 1890 area by 2010 (anywhere from 3 to 36 km2). The glacier surface lowered by 150–270 m near the terminus and the outlet glaciers collectively lost 60 ± 8 km3 of ice, which is equivalent to 0.15 ± 0.02 mm of sea-level rise. The volume loss of individual glaciers was in the range of 15–50%, corresponding to a geodetic mass balance between −0.70 and −0.32 m w.e. a−1. The annual rate of mass change during the post-LIA period was most negative in 2002–2010, on average −1.34 ± 0.12 m w.e. a−1, which is among the most negative mass balance values recorded worldwide in the early 21st century.

Download Full-text

Geodetic mass balance record with rigorous uncertainty estimates deduced from aerial photographs and LiDAR data – case study from Drangajökull ice cap, NW-Iceland

The Cryosphere Discussions ◽

10.5194/tcd-9-4733-2015 ◽

2015 ◽

Vol 9 (5) ◽

pp. 4733-4785 ◽

Cited By ~ 5

Author(s):

E. Magnússon ◽

J. M. C. Belart ◽

F. Pálsson ◽

H. Ágústsson ◽

P. Crochet

Keyword(s):

High Resolution ◽

Mass Balance ◽

Bias Correction ◽

Aerial Photographs ◽

Glacier Surface ◽

Ice Cap ◽

Uncertainty Estimates ◽

Lidar Dem ◽

Geodetic Mass Balance

Abstract. In this paper we describe how recent high resolution Digital Elevation Models (DEMs) can be used as constraints for extracting glacier surface DEMs from old aerial photographs and to evaluate the uncertainty of the mass balance record derived from the DEMs. We present a case study for Drangajökull ice cap, NW-Iceland. This ice cap covered an area of 144 km2 when it was surveyed with airborne LiDAR in 2011. Aerial photographs spanning all or most of the ice cap are available from survey flights in 1946, 1960, 1975, 1985, 1994 and 2005. All ground control points used to constrain the orientation of the aerial photographs were obtained from the high resolution LiDAR DEM (2 m × 2 m cell size and vertical accuracy < 0.5 m). The LiDAR DEM was also used to estimate errors of the extracted photogrammetric DEMs in ice and snow free areas, at nunataks and outside the glacier margin. The derived errors of each DEM were used to constrain a spherical variogram model, which along with the derived errors in ice and snow free areas were used as inputs into 1000 Sequential Gaussian Simulations (SGSim). The simulations were used to estimate the possible bias in the entire glaciated part of the DEM. The derived bias correction, varying in magnitude between DEMs from 0.03 to 1.66 m (1946 DEM) was then applied. The simulation results were also used to calculate the 95 % confidence level of this bias, resulting in values between ±0.21 m (in 2005) and ±1.58 m (in 1946). Error estimation methods based on more simple proxies would typically yield 2–4 times larger error estimates. The aerial photographs used were acquired between late June and early October. An additional bias correction was therefore estimated using a degree day model to obtain the volume change between the start of two hydrological years (1 October). This correction corresponds to an average elevation change of ~ −3 m in the worst case for 1960, or about ~ 2/3 of volume change between the 1960 and the 1975 DEMs. The total uncertainty of the derived mass balance record is mostly due to uncertainty of the SGSim bias correction, the uncertainty of the seasonal bias correction and the uncertainty of the interpolated glacier surface where data is lacking. The record shows a glacier-wide mass balance rate of Ḃ = −0.250 ± 0.040 m w.e. a−1 for the entire study period (1946–2011). We observe significant decadal variability including positive periods, peaking in 1985–1994 with Ḃ = 0.26 ± 0.11 m w.e. a−1. There is a striking difference if Ḃ is calculated separately for the western and eastern halves of Drangajökull, with a reduction of eastern part on average ~ 3 times faster than the western part. Our study emphasises the need of applying rigorous geostatistical methods for obtaining uncertainty estimates of geodetic mass balance, the importance of seasonal corrections of DEMs from glaciers with high mass turnover and the risk of extrapolating mass balance record from one glacier to another even over short distances.

Download Full-text

Use of an Unmanned Aerial Vehicle to assess recent surface elevation change of Storbreen in Norway

10.5194/tc-2016-292 ◽

2017 ◽

Cited By ~ 2

Author(s):

Walter Immerzeel ◽

Philip Kraaijenbrink ◽

Liss Andreassen

Keyword(s):

Mass Balance ◽

Unmanned Aerial Vehicle ◽

Glacier Surface ◽

Mountain Glacier ◽

Low Contrast ◽

Surface Mass ◽

Aerial Vehicle ◽

Geodetic Mass Balance ◽

Southern Norway ◽

Elevation Model

Abstract. Routinely and accurate monitoring of the outlines and surface mass balance of glaciers is essential. In this study an unmanned aerial vehicle (UAV) was used in September 2015 on a mountain glacier (Storbreen) in Norway to map the glacier outline, snow line and to derive a digital elevation model (DEM) of the glacier surface. The generated DEM has a relatively high accuracy with maximum horizontal RMSE of 0.36 m vertical RMSE of 0.44 m and the Structure for Motion algorithm also proved to be suitable under low contrast, high saturation fully snow covered conditions. A well distributed set of markers, measured by GPS, was required to generate a high quality DEM under the yielding conditions. The final UAV DEM was compared to a laser based DEM of 2009 and the annual geodetic mass balance between 2015 and 2009 was estimated to be between −0.71 ± 0.1 m w.e. and −0.75 m ± 0.1 w.e., which is in good agreement with the glaciological mass balance of −0.80 m ± 0.18 w.e. a−1. An analysis of the glacier outlines reveal that the glacier has lost 1.2 % of its surface area between 2009 and 2015. These findings confirm the strong mass loss and retreat of continental glaciers in southern Norway.

Download Full-text