Upload
christina-dawson
View
213
Download
1
Tags:
Embed Size (px)
Citation preview
Status and Plans of the National Geodetic Survey’s Gravity Database Update
Daniel R. Roman and Yan Ming Wang
October 13-14, 2005 Austin, Texas
DISCUSSION OUTLINE
• NGS-held point surface gravity measurements
• Problems in the current gravity database
• The first effort to fill in data gaps near shore
• Future Plans• Invitations
NGS-held point surface gravity measurements
• 2,155,662 surface gravity measurements scattered throughout North America
• mixture of NGS & NGA-proprietary data
Problems in the current gravity database:
• Tidal systems differ between NGS (tide-free) and NIMA-proprietary (mean tide) data
• Data reference NAD27 & NGVD29 but can be converted to NAD83 & NAVD88
• Data collected for a long time period (dating back more than 80 years), may contain local or regional biases
• Effect of subsidence and the Earth’s crustal movement on gravity has become considerable
• Data gaps in near shore and difficulty-to-access areas
The first effort to fill in data gaps near shore:
• NGS/NRL/GSFC joint airborne gravity and LIDAR mission in Golf of Mexico region
• Data were collected in May/June 2005• The misson’s goals are:
- To fill in data gaps near shore- Establish links between off-shore mean sea surface and the North America Vertical Datum 88 (NAVD88)
GRAVITY-LIDAR COLLECTION MISSION
Future Plans:
• The next study area will flow from the Florida panhandle through Louisiana into Texas along the Gulf coast
• Airborne missions over coastal and complete US continental are proposed
• A complete coastal and inland airborne survey is proposed
• Missions will be at 20 km cross track spacing and at 8.5 km altitude
Invitations:
• We are seeking corporations between government agencies, such as NGA, NRL, NASS and USGS.
• Research institutes and universities are welcome.• Private industry (oil companies and mapping companies) are
invited to participant.