MEETING THE CHALLENGES OF MEETING THE CHALLENGES OF DIFFICULT ENVIRONMENTS WITH DIFFICULT ENVIRONMENTS WITH AIRGrav AIRGrav Stefan Elieff Sander Geophysics Sander Geophysics
Sander Geophysics Founded in 1956 - currently 160 employees, 16 aircraft Head office at Ottawa International Airport, Canada World-wide operations – fixed-wing and helicopter High resolution airborne geophysics – petroleum, mineral, environmental − Magnetic − Gamma ray spectrometry − Gravimetry − LIDAR Laser Scanning − EM Sander Geophysics
Worldwide Operations Sander Geophysics
Mauritanian Sahara Desert Sander Geophysics
Jungles of Papua New Guinea Jungles of Papua New Guinea Sander Geophysics
Empty Quarter, Saudi Arabia Empty Quarter, Saudi Arabia Sander Geophysics
Ice Sheets and Glaciers of Antarctica Ice Sheets and Glaciers of Antarctica Sander Geophysics
Difficult Environments Difficult Environments Stakes are higher: costs, logistics, limited time osts, logistics, limited time Stakes are higher: c window for operations window for operations Fly often Fly often – Wide range of conditions Wide range of conditions – Reliable equipment Reliable equipment Fly efficiently Fly efficiently – All sensors collecting optimal data All sensors collecting optimal data – Optimal data throughout flight Optimal data throughout flight Sander Geophysics
SGL AIRGrav AIRGrav AIRBORNE GRAVITY AIRBORNE GRAVITY SGL System design: System design: – Three accelerometers (x y z) on a three axis Three accelerometers (x y z) on a three axis gyro stabilized platform gyro stabilized platform – Dual frequency GPS Dual frequency GPS receivers receivers – Gravity = inertial accelerations – GPS Gravity = inertial accelerations – GPS accelerations accelerations Excellent tolerance of aircraft motion Excellent tolerance of aircraft motion – Maintains accuracy in turbulence and while Maintains accuracy in turbulence and while following terrain (flying drape) following terrain (flying drape) – Short lead-ins to lines (about 1 minute) Short lead-ins to lines (about 1 minute) High resolution and accuracy High resolution and accuracy Sander Geophysics
Turbulence ● Hot, low altitude Influence of Turbulence - Sahara Desert Surveys ● No significant impact on gravity until turbulence Relative noise estimate extremes ● Other factors (ie GPS) dominant Relative turbulence for each line Sander Geophysics
Drape ● Instrument height limits (laser, spectrometer) ● Loss of resolution (attenuation with height) Sander Geophysics
Effect of altitude on airborne gravity data resolution 0 -5 -10 Gravity (mGal) 150 m -15 300 m 1500 m -20 -25 -30 0 20 40 60 80 Distance from start of line (km) Sander Geophysics
EARLIER ANTARCTIC AIRBORNE GRAVITY EARLIER ANTARCTIC AIRBORNE GRAVITY Science surveys since late 1970s Science surveys since late 1970s Successful, but with Successful, but with shortcomings shortcomings Limited resolution & accuracy ● Limited resolution & accuracy Long lead-ins to lines ● Long lead-ins to lines Inability to acquire accurate data ● Inability to acquire accurate data while following terrain (drape) while following terrain (drape) Prevents broader application in Prevents broader application in Antarctic research Antarctic research Sander Geophysics
IPY – AGAP PROJECT IPY – AGAP PROJECT International Polar Year International Polar Year 2007-2008 2007-2008 Lamont-Doherty Earth Lamont-Doherty Earth Observatory of Columbia Observatory of Columbia University (LDEO) University (LDEO) leading U.S. airborne leading U.S. airborne portion of the AGAP portion of the AGAP project project – A Antarctica's ntarctica's – Ga Gamburtsev mburtsev – P Province rovince Sander Geophysics
Science Goals: Science Goals: Map the hidden ● Map the hidden Gamburtsev Mountains Gamburtsev Mountains buried under ice (over buried under ice (over 4 km thick in places) 4 km thick in places) History of ice sheet – the ● History of ice sheet – the cradle of formation? cradle of formation? Tectonic history of ● Tectonic history of Antarctica Antarctica Locate places to drill for ● Locate places to drill for the oldest ice cores the oldest ice cores Subglacial lakes ● Subglacial lakes Sander Geophysics
IPY - AGAP: GRAVITY METER? IPY - AGAP: GRAVITY METER? Use commercial ● Use commercial gravity meter from gravity meter from exploration industry? exploration industry? Need to test suitability ● Need to test suitability for polar research for polar research and Antarctic and Antarctic environment first... environment first... Sander Geophysics
IPY - AGAP: GRAVITY METER? IPY - AGAP: GRAVITY METER? Calgary & Eureka tests Calgary & Eureka tests Summer 2007 Summer 2007 Sander Geophysics
IPY - AGAP: GRAVITY METER IPY - AGAP: GRAVITY METER SGL's AIRGrav system SGL's AIRGrav system selected for use in selected for use in Antarctica for AGAP Antarctica for AGAP Comparison of AIRGrav and Comparison of AIRGrav and GT-1A airborne gravimeters GT-1A airborne gravimeters for research applications. for research applications. Michael Studinger, Robin Michael Studinger, Robin Bell, and Nick Frearson, Bell, and Nick Frearson, Geophysics ,Vol. 73, No. 6 ,Vol. 73, No. 6 Geophysics November-December 2008 November-December 2008 Sander Geophysics
IPY - AGAP: 2008-2009 FIELD SEASON IPY - AGAP: 2008-2009 FIELD SEASON LDEO: ● LDEO: magnetic, ice magnetic, ice penetrating penetrating radar, laser radar, laser scanner scanner SGL: gravity, ● SGL: gravity, aircraft aircraft attitude attitude Kenn Borek Air: ● Kenn Borek Air: Twin Otter Twin Otter Sander Geophysics
Williams 'Field', McMurdo, Antarctica Williams 'Field', McMurdo, Antarctica Kenn Borek Twin Otter C-FSJB Kenn Borek Twin Otter C-FSJB Sander Geophysics
AGAP Airborne Science Team AGAP Airborne Science Team BAS Twin Otter VP-FBL BAS Twin Otter VP-FBL Sander Geophysics
Sander Geophysics
AGAP-South Field Camp Extremely remote – 600 km from South Pole, ● Extremely 1500 km from McMurdo ● -25ºC to -35ºC (plus wind chill) Sander Geophysics
Sander Geophysics
AGAP-South Field Camp ● Actual altitude: 3500m (11,500 ft) ● Physiological altitude: up to 14,000 ft Sander Geophysics
● Antarctica – a moving ice sheet ● GPS base stations are not stationary Sander Geophysics
Sander Geophysics
AGAP-S GPS Reference Station Motion 0.08 0.06 AGAP-South 0.04 0.02 5 mm per day UPS Y Offset (m) 0.00 movement -0.02 -0.04 -0.06 -0.08 -0.08 -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08 UPS X Offset (m) Sander Geophysics
AGAP-South Operations ● Logistical / Operational challenges ● Delays getting camp operational ● Fuel supply ● Weather ● Aircraft snags ● Short flying 'season' ● Must take advantage of every flying opportunity Sander Geophysics
AGAP-South Operations ● 53 flights: 55,000lkm of data between 22 nd December 2008 and 17 th January 2009 ● Most productive period: ● 21 flights in 6 days ● Round the clock flying: 4 flights per day, 22 hours per day, 4,000+ km per day. ● 40% of the survey completed during this period ● AIRGrav system – no delays, no downtime, through entire survey Sander Geophysics
Sander Geophysics
Gamburtsev Mountains as imaged by AIRGrav. Similar in size and character to the European Alps Sander Geophysics
Two days ago...first AGAP research paper published. Sander Geophysics
British Antarctic Survey (BAS) ● Traditional L&R airborne gravity meter modified by ZLS ● Flew northern area from AGAP-North camp Sander Geophysics
AGAP Performance Comparison AIRGrav BAS L&R AIRGrav BAS L&R ● Flown drape (benefits ● Flown constant height grav, mag, laser) (no laser instrument) ● 3.5km lead-ins ● 15-20km lead-ins ● 3500m resolution ● 8000m resolution ● 1 mGal crossover ● 3.5 mGal crossover errors errors Sander Geophysics
Continued Continued LDEO / SGL LDEO / SGL collaboration collaboration Sander Geophysics
NASA IceBridge NASA IceBridge ● Multi-year, multi-instrument, Multi-year, multi-instrument, multi-aircraft campaign multi-aircraft campaign ● Monitor ice at Earth's poles Monitor ice at Earth's poles ● Bridging the gap between Bridging the gap between ICESat (ended 2009) and ICESat (ended 2009) and ICESat 2 (launch 2015?) ICESat 2 (launch 2015?) Sander Geophysics
P-3 in Arctic P-3 in Arctic DC-8 in Antarctic and Arctic DC-8 in Antarctic and Arctic Sander Geophysics
IceBridge Radar & Laser IceBridge Radar & Laser Sander Geophysics
Role of airborne gravity Role of airborne gravity Sander Geophysics
Role of airborne gravity Role of airborne gravity Sander Geophysics
Role of airborne gravity Role of airborne gravity ● Sea ice surface rises, no open leads... Thicker ice or geoid? ● Horizontal gravity components from AIRGrav Source: NRCan Sander Geophysics
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