Surveys

Our first attempts to image the Furggwanghorn rock glacier involved acquiring surfaced-based GPR data using two different acquisition systems and three different antennae (second to fourth columns in Table 3 and Fig. 411 a - c). GPR data were recorded along multiple lines during the Winter / Spring of 2010, 2011 and 2012 and during the Summer of 2012. See the caption to Fig. 412 for the locations of three of these lines (G1 - G3).

../../../_images/pulseEKKO_gprsys.png — Fig. 411 Winter/Spring deployment of different GPR systems: (a) 50 MHz Mala Rough Terrain Antennae, (b) Sled mounted 50 MHz pulseEKKO PRO, (c) rigid frame mounted 25 MHz pulseEKKO PRO and (d) helicopter mounted 60 MHz GSSI SIR-3000.

Table 3: Data acquisition systems used for surface-based GPR surveying the Furggwanghorn rock glacier.

Division	Ground	Ground	Ground	Helicopter
System	pulseEKKO PRO	pulseEKKO PRO	Mala RTA	GSSI SIR-3000
Nominal Antennae frequency (MHz)	50	25	50	60
Antenna separation (m)	2	4	4	2
Antenna configuration	Parallel-broadside	Perpendicular-broadside	Parallel-endfire	Parallel-broadside
Sampling rate (ns)	1.6	3.2	1.46	1.46
Trace length (ns)	2000	5040	1547	3000
Antenna transportation	Sled	Rigid frame	Snake antennae	Helicopter
Positioning	Diff. GPS	Diff. GPS	Diff. GPS	Diff. GPS

After obtaining disappointing results from the surface-based GPR surveys, a few lines of H-GPR data were recorded in the Winter / Spring of 2012. The high quality of the 2012 H-GPR images prompted the full 3D GPR survey during the Winter / Spring of 2013. A total of ~9000 m of H-GPR data were acquired 15 ‑ 20 m above ground along sixteen ~450 m long east-west lines separated by an average of ~10 m and along four ~340 m long north-south lines (Fig. 412). In addition to crossing the active rock glacier (ARG in Fig. 409), the lines traversed parts of the rock glacier’s root zone (RGRZ), inactive and relict rock glaciers (IRG and RRG), the talus, and several bedrock outcrops.