CEE 6100 / SCAS 6600Other Systems:

Airborne Electromagnetic Method

Airborne Electromagnetic MethodThe Airborne Electromagnetic Method (AEM) consists of inducing a current using an antenna on a fixed wing aircraft or helicopter flying at low altitude.

• Low frequency: 2.4 KHz (125 km) - 900 MHz; 0.3 m)• Induces eddy currents in the ground/water/ice• Detects variations in conductivity of the ground• Sensitive to the presence of conductive materials

(salt, salt water, graphite, clays, sulfide minerals, …)• Can detect variations in conductivity to depths of 100s

or even 1000s of meters in favorable conditions.

30𝑥𝑥 (𝐺𝐺𝐺𝐺𝐺𝐺)

= 𝑦𝑦 (𝑐𝑐𝑐𝑐)300

𝑥𝑥 (𝑀𝑀𝐺𝐺𝐺𝐺)= 𝑦𝑦 (𝑐𝑐)

300𝑥𝑥 (𝐾𝐾𝐺𝐺𝐺𝐺)

= 𝑦𝑦 (𝑘𝑘𝑐𝑐)

Airborne Electromagnetic Method

GEOTEM AEM System:Aircraft survey altitude ~ 120 m. Note the AEM receiver bird being deployed (inset).

Operating range: 387-102700 Hz (770-3 km)

Vrbancich, Julian, ‘Airborne Electromagnetic Bathymetry Methods for Mapping Shallow Water Sea Depths’, International Hydrographic Review, 5 (2004), 59–84

Airborne Electromagnetic Method

ASEG AEM Workshop – Perth, November 2012

Airborne Electromagnetic MethodThe DIGHEM frequency domain EM system is configured in a cylindrical “bird” which is carried beneath a helicopter. DIGHEM employs 5 pairs of transmitting and receiving coils; three horizontal coplanar coil pairs at frequencies of nominally 900 (333 km), 7200 (42 km) and 56000 Hz (5 km), and two vertical coaxial coil pairs at approximately 1000 (300 km) and 5500 Hz (54 km). The coil separation is 8 metres on all frequencies except 56000 Hz, which has a coil separation of 6.3 metres due to its high signal strength.

The DIGHEM system uses multiple frequency electromagnetic fields to measure and map the electrical conductivity of the earth in three dimensions in the top 150 metres of the earth. The coplanar coil pairs provide greatest sensitivity to the conductivity of the earth, to layers and to subtle changes in conductivity. They are also least sensitive to the direction of the survey. The coaxial coil pairs produce the strongest anomalies from vertical conductors, such as steeply dipping massive sulphides and cultural or human-made conductors

http://www.cgg.com/default.aspx?cid=7754&lang=1

CEE 6100/CSS 6600 Remote Sensing Fundamentals © W. Philpot, Cornell University Fa 2018 Other Systems 6

(a): the frequency-domain helicopter DIGHEMV AEM system (~ 8 m length) during survey over Sydney Harbour (Vrbancich, et al., 2000a,b). The smaller bird between the helicopter and the DIGHEM bird is a magnetometer bird; (b): The HoistEM time-domain helicopter AEM bird, located over the Sow and Pigs reef during a survey of Sydney Harbour (Vrbancich & Fullagar, 2004, 2007b). The transmitter loop (~ 22 m diameter) is attached to the extremities of the poles and the multi-turn receiver loop is located on the same plane, at the centre of the system.

Airborne Electromagnetic Method

http://www.cgg.com/default.aspx?cid=7776&lang=1

TEMPEST’s features include:Extremely broad bandwidth, 25 Hz to 37500 Hz (12,000-54 km), achieved through use of a square transmitter waveform with rapid transmitter switching rates, sophisticated high bandwidth receiver coil design and high data sampling rate (75kHz), delivers high resolution mapping of both deep and shallow targets.

http://209.91.124.56/publications/recorder/2010/03mar/Mar2010-Airborne-Electromagnetic-Methods.pdf?file=03mar/Mar2010-Airborne-Electromagnetic-Methods.pdf

In the Fyn area, Denmark, the thickness of a resistive aquifer above a saline aquifer was of interest. An airborne survey was flown to map the depth to the top of the saline layer, which was essentially the thickness of the aquifer. The colors inside the circles represent the thickness estimated from ground TEM data. Agreement is good except in the low resistivity zone on the western edge where some conductive clays near the surface violate the assumption of a resistor over a conductor.

Airborne Electromagnetic Method

Paine, J. G., and Collins, E. W., 2003, Applying airborne electromagnetic induction in groundwatersalinization and resource studies, West Texas, in Proceedings, Symposium on the Application of Geophysics to Engineering andEnvironmental Problems: Environmental and Engineering Geophysical Society, p. 722-738

Airborne Electromagnetic Method

CEE 6100/CSS 6600 Remote Sensing Fundamentals © W. Philpot, Cornell University Fa 2018 Other Systems 10

Ice Sheet Remote Sensing

Wang, Z., Gogineni et al. (2016). Multichannel Wideband Synthetic Aperture Radar for Ice Sheet Remote Sensing: Development and the First Deployment in Antarctica. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 9(3), 980–993. http://doi.org/10.1109/JSTARS.2015.2403611

The new system has a maximum bandwidth of 260 MHz andoffers the ability to measure ice sheets thickness and map internal layers with a range resolution of about 40 cm in the ice and image the ice-bed interface with an azimuth resolution of 2.5 m.

CEE 6100/CSS 6600 Remote Sensing Fundamentals © W. Philpot, Cornell University Fa 2018 Other Systems 11

Ice Sheet Remote Sensing

CEE 6100/CSS 6600 Remote Sensing Fundamentals © W. Philpot, Cornell University Fa 2018 Other Systems 12

(A) Regional view of northwest Greenland. Inset map shows location relative to whole of Greenland. Magenta box identifies location of (B) to (D).

(B) A 5-m ArcticDEM mosaic over eastern Inglefield Land. Colors are ice surface velocity. Blue line illustrates an active basal drainage path inferred from radargrams.

(C) Hillshade surface relief based on the ArcticDEM mosaic, which illustrates characteristics such as surface undulations. Dashed red lines are the outlines of the two subglacial paleochannels. Blue lines are catchment outlines, i.e., solid blue line is subglacial and hatched is supraglacial.

(D) Bed topography based on airborne radar sounding from 1997 to 2014 NASA data and 2016 Alfred Wegener Institute (AWI) data. Black triangles represent elevated rim picks from the radargrams, and the dark purple circles represent peaks in the central uplift. Hatched red lines are field measurements of the strike of ice-marginal bedrock structures. Black circles show location of the three glaciofluvial sediment samples described in table S1.

Geomorphological and glaciological setting of Hiawatha Glacier, northwest Greenland.Kjær, K. H. et al. (2018). A large impact crater beneath Hiawatha Glacier in northwest Greenland. Science Advances, 4(11), eaar8173. http://doi.org/10.1126/sciadv.aar8173

CEE 6100/CSS 6600 Remote Sensing Fundamentals © W. Philpot, Cornell University Fa 2018 Other Systems 13

Radiostratigraphy of Hiawatha Glacier

(A) Regional view of northwest Greenland. Inset map shows location relative to whole of Greenland. Magenta box identifies location of (B) to (D).

(B) A 5-m ArcticDEM mosaic over eastern Inglefield Land. Colors are ice surface velocity. Blue line illustrates an active basal drainage path inferred from radargrams.

(C) Hillshade surface relief based on the ArcticDEM mosaic, which illustrates characteristics such as surface undulations. Dashed red lines are the outlines of the two subglacial paleochannels. Blue lines are catchment outlines, i.e., solid blue line is subglacial and hatched is supraglacial.

(D) Bed topography based on airborne radar sounding from 1997 to 2014 NASA data and 2016 Alfred Wegener Institute (AWI) data. Black triangles represent elevated rim picks from the radargrams, and the dark purple circles represent peaks in the central uplift. Hatched red lines are field measurements of the strike of ice-marginal bedrock structures. Black circles show location of the three glaciofluvial sediment samples described in table S1.