Mapping Glacier Dynamics and Proglacial Wetlands with a Multispectral UAV at 5000m in the Cordillera Blanca, Peru Oliver Wigmore, Bryan G. Mark
AGU2015, Dec 14-18 Abstract: C41D-0719
The Ohio State University, Department of Geography and Byrd Polar and Climate Research Center Contact:
[email protected] www.oliverwigmore.com
ABSTRACT
RESULTS – GLACIER MAPPING
RESULTS – WETLAND MAPPING
The glaciers of the Cordillera Blanca, Peru are rapidly retreating as a result of rising temperatures, transforming the hydrology and impacting the socio-economic and environmental systems of the Rio Santa basin. Documenting the heterogeneous spatial patterns of these changes to understand processes of water storage and flow is hindered by technologic and logistic challenges. Highly complex topography, cloud cover and coarse spatial resolution limit the application of satellite data while airborne data collection remains costly and potentially dangerous. However, recent developments have made Unmanned Aerial Vehicle (UAV) technology a viable and potentially transformative method for studying glacier dynamics and proglacial hydrology.
STUDY AREA
2015 10cm DEM and 5cm RGB Orthomosaic
2014 10cm DEM and 5cm RGB Orthomosaic
2015 Error Histogram
4600 4560 4540
R2 = 1.000 Mean Diff. = -0.0234m Sdev. = 0.1400m
4520 4500
GPS Ell.H minus DEM Ell.H (m)
4600
8
Check Points GCPs
6 4 2
4480 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4
Accuracy Assessment of 2015 DEM
10
Frequency
Check Points GCPs
4580
Ell.H DGPS
8 7 6 5 4 3 2 1 0
Accuracy Assessment of 2014 DEM
4460 4460 4480 4500 4520 4540 4560 4580 4600
Ell.H DEM
4580
Ell.H DGPS
2014 Error Histogram
Frequency
The extreme altitudes (4000-6700m) of the Cordillera Blanca limit the use of 'off the shelf' UAVs. Therefore we developed a low cost multispectral (visible, near-infrared and thermal infrared) multirotor UAV capable of conducting fully autonomous aerial surveys at elevations over 5000m within the glacial valleys of the Cordillera Blanca. Using this platform we have completed repeat aerial surveys (in 2014 and 2015) of the debris covered Llaca Glacier, generating highly accurate 10-20cm DEM's and 5cm orthomosaics using a structure from motion workflow. Analysis of these data reveals a highly dynamic system with some areas of the glacier losing as much as 18m of vertical elevation, while other areas have gained up to 11m of elevation over one year. The magnitude and direction of these changes appears to be associated with the presence of debris free ice faces and meltwater ponds. Additionally, we have mapped proglacial meadow and wetland systems. Thermal mosaics at 10-20cm resolution are providing novel insights into the hydrologic pathways of glacier meltwater including mapping the distribution of artesian springs that feed these wetland systems. The high spatial resolution of these UAV datasets facilitates a better understanding of the spatial variability in and controls on glacier dynamics and proglacial surface/subsurface hydrology within the Cordillera Blanca. We discuss the technical details of the platform, the challenges of conducting UAV surveys at high elevation and share insights from our findings at Llaca Glacier and within the proglacial wetland systems.
Streamflow Direction
4560 4540
R2 = 1.000 Mean Diff. = -0.0009m Sdev. = 0.0442m
4520 4500 4480
0 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4
GPS Ell.H. minus DEM Ell.H. (m)
4460 4460 4480 4500 4520 4540 4560 4580 4600
Ell.H DEM
RESULTS – GLACIER CHANGE
High resolution (5-10cm) multispectral data sets facilitate investigation of highly heterogeneous water storage (soil moisture), hydrologic pathways (springs) and river mixing. Also, plant health and grazing impacts.
N
CONCLUSIONS
UAV DESIGN AND METHODOLOGY
• Operation of UAV’s in high altitude mountain environments is tricky but possible • SfM DEM’s can provide unique insights into glacier changes in the tropics that are difficult and costly to obtain through other methods e.g. TLS, aerborne LiDAR • Glacier change at Llaca is extremely dynamic – the lake and moraine regions are of particular interest due to their relation to GLOF hazards downstream • Debris cover, exposed ice cliffs and surface ponds control patterns of observed glacier change • High resolution multispectral data can provide detailed information about the hydrologic processes occurring within the proglacial meadow and wetland systems • Extreme heterogeneity is impossible to understand using traditional methods of field survey and/or satellite remote sensing
ACKNOWLEDGEMENTS • 1m carbon fibre hexacopter • Custom design for high altitude 4000-5500masl flight • Fully autonomous 3DR APM/Pixhawk autopilot • Sensors for Visible, Near Infrared and Thermal data • Image capture triggered by CHDK and video feed (TIR) • GCP targets installed and surveyed to ~1cm accuracy • Structure from Motion (SfM) processing with Agisoft Photoscan Pro
• 156,000m3 of glacier ice lost over one year • 0.76m vertically averaged across glacier surface • 18m max loss (at calving face collapse), 11m max gain (large boulders) • Significant changes in lake areas – ice cored sediment and moraine movement • Max velocity 27m/yr on upper section, ~4m/yr at terminus
Funding and equipment support gratefully acknowledged from: NSF - #1434248, GSS, DDRI: Doctoral Dissertation Research: Assessing Variability in High Elevation Soil Moisture: Integrating Unmanned Aerial Vehicles, Satellites, and Field Hydrology. Pis: B.G. Mark, O. Wigmore, Ohio State Univ. NSF - #1010550, BCS – BE: DYN COUPLED NATURAL-HUMAN: Collaborative Research: Hydrologic Transformation and Human Resilience to Climate Change in the Peruvian Andes. PIs: B.G. Mark, J. Bury, UCSC; K. Young, UT, Austin; M. Carey, U of Oregon. UNAVCO – This material is based on [data, equipment, and/or engineering] services provided by the UNAVCO Facility with support from the National Science Foundation (NSF) and National Aeronautics and Space Administration (NASA) under NSF Cooperative Agreement No. EAR-0735156. DRS Technologies – Thermal Camera Donation American Philosophical Society – Lewis and Clark Exploration Fund American Explorers Club – Student Research Grant American Geographical Society – Council Fellowship Geological Society of America – Student Research Grant
