GRAV-D on the Airfield: How we accomplish airborne gravity data collection

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GRAV-D on the Airfield How we accomplish
airborne gravity data collection

• NGS Gravity Geoid Brown Bag
• December 1, 2009
• Theresa Diehl

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Where to survey?

• Time of Year
• Storms Hurricanes, Noreasters, Tornados
• Prevailing winds and weather patterns
• Aircraft Available
• Maximize range per flight

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Survey Layout

• What features do you need to capture?
• Where are the best airports to operate out of?

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Flight Plans

• How many hours for each flight?
• How long to complete the survey?

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Pre-Survey Site Visit

• Discuss our needs with airport contacts
• Same parking spot every day, near power
• Freedom of access to tarmac location of GPS
• Office space
• Accommodations available for group near airport

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Pre-Survey Site Visit

• Associated ground survey for gravity tie
• Best place for new absolute reading/existing one
• New mark at airport

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Airborne Instrument Installation

• TAGS

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Airborne Instrument Installation
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Airborne Instrument Installation
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Basestation Setup
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An Ideal GRAV-D Day (Citation)

• 7am Instrument start up
• 8am Pilot briefing/weather/flight plans
• 9am Plane Take off
• On ground QC processing of yesterday evenings
  flight
• 1pm Landing
• Lunch/Briefing for next flight
• 2pm Take off
• On ground QC processing on this mornings flight
• 6pm Landing
• 8pm Shut down complete

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Divide and Conquer

• 7am Instrument start up
• 8am Pilot briefing/weather/flight plans
• 9am Plane Take off
• On ground QC processing of yesterday evenings
  flight
• 1pm Landing
• Lunch/Get ready for next flight
• 2pm Take off
• On ground QC processing on this mornings flight
• 6pm Landing
• 8pm Shut down complete

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Step 1 Get plane off the ground

• Turn on all GPS
• Turn on and test gravimeter
• Start flight log of events
• Weather!

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Weather

• Clouds
• Turbulence
• Wind
• Icing
• Warnings
• Smoke/Fog
• Mid-day heating changes weather

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Step 2 Collect data
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Landing
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Step 3 Download Data/Documents

• Basestation GPS (3)
• Aircraft GPS (1)
• Aircraft IMU GPS (1)
• Gravimeter Readings (2 screenshots)
• Paper Flight Logs
• Magnetometer
• Download 1s CORS data
• GoogleDocs Survey Logs

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Step 3 Quality Control

• Are all instruments performing well?
• Is the gravity of good quality?

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Step 4 Troubleshoot

• Noisy gravity
• PDOP spikes
• Instrument problems
• Personnel illnesses
• Active military airspace
• Aircraft maintenance problems
• Weather worse than forecast
• The unexpected and unusual (GPS jamming, holes in
  the runway, bird delays)

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Repeat as Necessary
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Completion
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TAGS Team
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• Are
• You
• Here
• Next?

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Questions?

• Thank you!