geodesy basics for kentucky gis
DESCRIPTION
TRANSCRIPT
Ross MackayKentucky Geodetic Advisor
Geodesy Basicsfor
Kentucky GIS
2009 Kentucky Geospatial SummitFrankfort, KentuckySeptember 10, 2009
ellipsoid
Datum
geoid
Datum
• Latitude • Longitude • Height • Scale • Gravity• Orientation
National Spatial Reference SystemNSRS
Geodesy layer
and how these values change with time
Datum
h
LandSurface
h = Ellipsoidal Height
Ellipsoid
Geoid model
?
H
H = “elevation”
N = Geoid height
H ≈ h - N
Datum
N
Passive Control
TRANSCONTINENTAL ARC OF TRIANGULATION
http://www.holoscenes.com/cgi-bin/moin.cgi/TranscontinentalTriangulation
Map courtesy of Jim Irwin
KGRN (NSRS 2007) 863
Horizontal 2079
Vertical 10123
Datum
Active Control
National CORS Network
1381 National CORSSeptember 1, 2009
CORS
• Paducah, KYTA
• Jackson, KYTJ
• Morehead, KYMH
• Cumberland, KYCB
• Somerset, KYSC
• Campbellsville, KYCB
• Taylor Lake, Lou5
• Madisonville , KYTB
• Bowling Green, KYTC
• Elizabethtown, KYTD
• Louisville, KYTE
• Covington, KYTF
• Lexington, KYTG
• Somerset, KYTH
• Flemingsburg, KYTI
• Manchester, KYTK
• Pikeville, KYTL
• Greenbo Lake SRP, KYGB
• Dale Hollow SRP, KYDH
• Rough River SRP, KYRR
CORS
Hyperactive Control
NSRS
NSRS
NAD 83 vs. ITRF00
2.2 meters
NAD 83 origin
ITRF 00 origin
Earth’s
Surface
h83
h00
Identically shaped ellipsoids (GRS-80)a = 6,378,137.000 meters (semi-major axis)1/f = 298.25722210088 (flattening)
NSRS
NAVD 88Referenced to Father’s Point
NSRS
GRAV-DNGS 10-Year Plan
NSRS
Ten-Year Milestones (2018)
• NGS will redefine the NSRS vertical datum based on GNSS and a gravimetric geoid.
• NGS will redefine the NSRS horizontal datum, removing disagreement with the ITRF.
NSRS
Predicted positional changes fordatums in 2018
(Florida example)
Horizontal = 0.82 m (2.7 ft)
Ellipsoid Height
=
- 1.55 m (- 5.1 ft)
Predicted with HTDP
Orthometric Height
=
- 0.04 m (- 0.1 ft)
Predicted with HTDP and USGG2009
NSRS
