The Effects of Reflector Geometry on Radar Data Acquisition

The Effects of Reflector Geometry on Radar Data Acquisition

International Symposium on Radioglaciology 9/09/2013

Nicholas Holschuh, Sridhar Anandakrishnan, Knut Christianson

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Objectives of RESCo

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Historic Objectives•Determine the depth to (and geometry of) the

basal reflector

•Describe the internal structure of the ice sheets using the internal reflecting horizons (IRHs)

Modern Objectives•Use return powers from basal reflectors to

determine dielectric properties of the ice-bed interface

•Analyze the spectral quality of reflectors to uniquely identify layers through space

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MotivationCo

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The brightest reflectors are sometimes traceable through the lossy region …but at other times, are completely lost in the noise…

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What is the source of the data loss?

- Affects deeper reflectors more than shallow ones- Appears to be related to reflector slope- More prevalent in the High Frequency Airborne Data

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Assumptions - Specularity

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Internal Reflectors: Specular(Obey the Law of

Reflection)

Basal Reflectors: Diffuse

Reflection Coefficient

Reflection Coefficient +

Angular Distribution

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Ground Survey

Airborne Surveyn = 1 + 0.851ρ

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Ground Survey Airborne Survey

Refraction Limits:

Ground Survey – 49ºAirborne Survey – 34º

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StackingIn

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d)Stacking Controls

1) Radar Frequency2) Reflector Dip3) Stacking Distance

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Stacking – 1m Posting Interval

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0.00090.00210.01790.01950.04681

0.00260.02240.02950.03020.08211

0.01180.02520.03020.04790.09851

0.02250.04050.07090.09850.20271

0.94620.96190.97680.98910.9971

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Stacking Amplitude LossIn

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Radiation PatternIn

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Describes the angular distribution of the gain for a given radar antenna (Typically optimized for Nadir)

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Caveats - SpecularityIn

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Offsets 0 – 1400m (100m)

Transmitter

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Areas of intense deformation (and therefore glaciological interest) are prone to internal data loss

Amplitude loss due to reflector geometry should be corrected for if dipping beds are used in amplitude analysis.

Loss is ultimately a function of radar design and data collection methods. Choosing appropriate radars (frequency), platform, and stacking

distances can minimize data loss.

Nicholas Holschuh – [email protected]: Sridhar Anandakrishnan

Richard AlleyCollaborator: Knut Christianson

Questions?

This material is based upon work supported by the National Science Foundation Graduate

Research Fellowship Program under Grant No. DGE1255832.

We would like to acknowledge the use of data products from CReSIS generated with support from NSF grant ANT-0424589 and NASA grant NNX10AT68G.

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The Effects of Reflector Geometry on Radar Data Acquisition

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