Height ModernizationMaking the Most of the Indiana HARN and the INDOT CORS
Height ModernizationMaking the Most of the Indiana HARN and the INDOT CORS
March 14, 2007By
William A. Schmidt, PE, LSManager of Aerial Engineering,
INDOTThomas A. Mahon, PE, LS
Survey Group Manager, Woolpert Inc
Background – Surveying Infrastructure - Horizontal
Background – Surveying Infrastructure - Horizontal
• NAD 27 – Best fit Spheroid for North America
• Fifty nine years of terrestrial, local surveying by the general public
• Line of sight required (Bilby towers)• Regional or large scale projects only
conducted by National Geodetic Survey
• Highest achievable relative accuracy was 1:100,000
• Network accuracy 10 m
Background - Surveying Infrastucture (cont’d)Background - Surveying Infrastucture (cont’d)
Background – Surveying Infrastructure - HorizontalBackground – Surveying Infrastructure - Horizontal
•NAD 83(86) – Best fit Global Ellipsoid, conventional observations along with satellite triangulation, Doppler positions, and VLBI– Incorporated satellite (non-GPS)
observations into conventional data sets
– Largest solution of simultaneously adjusted equations up until that time
– 400,000 unknowns and 1,800,000 (observations) equations
Background – Surveying Infrastructure - HorizontalBackground – Surveying Infrastructure - Horizontal
•NAD 83(86) Issues– Not GPS-able– Poor accessibility– Irregularly spaced– Positional accuracy
•Relative 1:100,000•Network 1 m
Surveying Infrastructure – Horizontal (cont’d)Surveying Infrastructure – Horizontal (cont’d)
•Along came GPS•Private surveyors began finding
issues with existing control•Large scale surveys no longer the
domain of government surveyors•Projections and datums used•More ties to state plane coordinates•Both horizontal and vertical control in
one operation•Overall horizontal accuracy improving
Surveying Infrastructure in Indiana – HARNsSurveying Infrastructure in Indiana – HARNs
•“GPSABLE” Clear Horizons for Satellite Signal Acquisition
•EASY ACCESSIBILITY Few Special Vehicle or Property
Entrance Requirements
•REGULARLY SPACEDAlways within 20-100 Km
•HIGH HORIZONTAL ACCURACYA-Order (5 mm + 1:10,000,000)B-Order (8mm + 1:1,000,000)
Surveying Infrastructure in Indiana – HorizontalSurveying Infrastructure in Indiana – Horizontal
• Indiana HARN Phase I – 1997 (GPS1200)• Indiana HARN Phase II – 1998 (GPS1200)• Indiana HARN last of all 50 state HARN’s•No state HARN has better vertical
component•NAD 83(97) Statewide Readjustment by
NGS• ‘NAD 83’ no longer enough to define
adjustment• Indiana HARN Phase III - 2003 (GPS1850)
– FBN Vertical Enhancement Survey
High Accuracy Reference Network Positional AccuracyHigh Accuracy Reference Network Positional Accuracy
•HARN Stations– Network (absolute): 0.1 m– Relative
•B-order: one part per million• A-order: one part per 10 million
•CORS Stations– 0.01 m
Indiana HARN 1997/1998Indiana HARN 1997/1998
Phases of Indiana Surveying Infrastructure – Horizontal (cont’d)
Phases of Indiana Surveying Infrastructure – Horizontal (cont’d)
•HARN Participants:– HARN Phase I - Collaborative effort
between federal government, local government, private contractors (The Schneider Corporation & Plumb-Tuckett) and various volunteers
– HARN Phase II - Private contractor (Woolpert LLP)
– HARN Phase III - federal government, local government and various volunteers. No private contractor.
Indiana HARN Components: FBN/CBNIndiana HARN Components: FBN/CBN
•The Indiana HARN consists of stations maintained by the federal government and those maintained by the locals (anyone other than the federal government)
•HARN – High Accuracy Reference Network (161 Total Points)
•FBN – Federal Base Network (21), a subset of HARN stations sufficiently dense for the federal government to meet their surveying obligations within the state (100 km)
•CBN – Cooperative Base Network (140), all other HARN stations, more densely spaced to meet local needs.
Indiana HARN w/ FBN StationsIndiana HARN w/ FBN Stations
GPS & CLASSICAL ADJUSTMENTS COMPLETEDGPS ADJUSTMENT COMPLETED
1990
-GPS1
70
1990-GPS120
1991GPS222
1992GPS366
1997GPS11791992
GPS412
1992 GPS3831992
GPS450
1992GPS419
1992GPS394
1992GPS341
1993
1993 GPS585
1993 GPS667
1992GPS376
1995GPS887
.
1991GPS197
GPS2601991
1995GPS908
GPS610
1993 GPS725
1993
1994GPS404
GPS611
1994GPS633
1991 GP S291 reobs 9/97
1994 GPS721
reos 7/96 GPS1047
reos 1/96 GPS936
1997GPS1133
reos-6/95-GPS904
1995GPS852
1995GPS882
1993GPS606
1996GPS10481996
GPS8051996GPS941 1994
GPS7301996GPS1121
1997GPS1178
1997 GPS 12001997
GPS1150
reos-1996
Horizontal Control StationsHorizontal Control Stations
•A-order (13@1:10,000,000 horizontal)Adjusted to VLBI stations (NCMN 7291
Bloomington), CORS stations and other FBN stations
•B-order (148@1:1,000,000 horizontal)Adjusted to A-order stations
•C-order (all 1st, 2nd, and 3rd order stations)
Rubber sheeted to A & B-order stations
Indiana FBN Portion of the Indiana HARNIndiana FBN Portion of the Indiana HARN
Horizontal AdjustmentsHorizontal Adjustments
•NAD 83(97)– adjusted horizontal coordinates in
Indiana based on the first two HARN campaigns
– adjustment based on NAD 83(CORS) which had been adjusted in 1996
– adjustment tied into surrounding readjustment
– adjusted coordinates moved on the order of magnitude of ±1’ in Indiana
– adjusted only satellite observations and rubber sheeted conventional control into HARN stations
Horizontal AdjustmentsHorizontal Adjustments
•NAD 83(NSRS2007)– NSRS - National Spatial Reference System– readjustment of all GPS data in the
National Spatial Reference System simultaneously, not just a state or regional readjustment
– adjustment tied to CORS network as of 2002
– adjusted data in Indiana to be available Spring 2007
– states on stable North American plates will not be given an epoch date (considered fixed)
NAD 83(NSRS2007)NAD 83(NSRS2007)
Phases of Surveying Infrastructure – VerticalPhases of Surveying Infrastructure – Vertical
•NGVD 29 – National Geodetic Vertical Datum of 1929 (sea level)
•Thousands and thousands of km of level loops run since 1929
•NAVD 88 – North American Vertical Datum of 1988
•Many monuments have move or been destroyed over the years
Phases of Indiana Surveying Infrastructure – Orthophotography & DEM
Phases of Indiana Surveying Infrastructure – Orthophotography & DEM
•Statewide Digital Color Orthophotography – 2005
•Statewide Color Infrared Aerial Photos – 2005
•Statewide Digital Elevation Model – 2005
•Statewide Digital Surface Model – 2005
•gis.iu.edu•Google Earth
What’s Next – Height ModernizationWhat’s Next – Height Modernization
•Height Modernization is any program aimed at improving elevation estimates
•Typical activities have included:– differential leveling establishing/re-
establishing elevations on horizontal control stations
– survey mark recovery and remonumentation
– GPS surveying establishing horizontal positions and ellipsoidal heights on bench marks
– Gravity data observations for inclusion in the national geoid model
Height Modernization in IndianaHeight Modernization in Indiana
•Supplements the HARN and INDOT CORs
•To be done in phases•Phase I – differential leveling
– By INDOT District starting in Vincennes District
•Phase II – GPS observations on additional bench marks
Height Modernization in Indiana – Phase I (Vincennes)
Height Modernization in Indiana – Phase I (Vincennes)
Height Modernization in Indiana – Phase IHeight Modernization in Indiana – Phase I
125 miles of leveling in Vincennes District
•$1,500/mile•$190,000 for Vincennes District•Extrapolating to entire state
$1,140,000
•Funding for OISGA– $60,000
•Total for Phase I - $1.2M
Height Modernization in Indiana – Phase I ActivitiesHeight Modernization in Indiana – Phase I Activities
•Virtual Mark Recovery•Actual Mark Recovery•Coordination with INDOT CORS•Planning and Route Selection•Differential Leveling•Adjustment and Report
Height Modernization in IndianaHeight Modernization in Indiana
•Questions?
