Texas Height Modernization and Texas Spatial Reference Center

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Texas Height ModernizationandTexas Spatial
Reference Center
Gary Jeffress, Ph.D., RPLS Director, Conrad
Blucher Institute for Surveying and Science Texas
AM University-Corpus Christi
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It is about better measurement of heights or
elevations in Texas

• How high above Mean Sea Level?
• Do I live in a flood zone?
• Can I get flood insurance?

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Why do we need accurate elevations?
Austin, 1991
Houston, 2001

• Lives are lost and
• Billions of property are lost.

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Flooding in Austin 2001
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• Flooding in Central Texas in 2002 on the
  Guadalupe River

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More recently El Paso, July 2006
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The cost of flooding in Texas
Dates Dec 18 to 23, 1991 Oct 17-18, 1998 June 6 to 9, 2001 Nov 15, 2001 June 30-July 7, 2002
Location Central Texas South Central Texas Southeast Texas (Houston) Central Texas South Central Texas
Max. Rainfall 15.5 in. 30 in. 36 in. 14 in. 35 in.
Deaths 10 32 22 10 12
Approx. Damage 43 Million 1.5 Million 5 Billion 11.4 Million 1 Billion
From www.floodsafety.com
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What about coastal waters?
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NAVD
NGVD
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So, the US Quad sheets are very
out-of-date.Hence, the need for
StratmapandLIDAR Mapping.What controls this
new mapping?
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Many benchmarks have been destroyed, or worse,
unreliable.
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The solution.
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How do we observe elevation?

• Using a level instrument and
• Rods graduated in feet.

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Modern levels are digital
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VERTICAL DATUMS

• A set of fundamental elevations to which other
  elevations are referred.

H Orthometric Height (NAVD 88)
H h - N
h Ellipsoidal Height (NAD 83)
N Geoid Height (GEOID 03)

TOPOGRAPHIC SURFACE
h
H
N
GEOID03
Geoid Mean Sea Level
Ellipsoid GRS80
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COMPARISON OF VERTICAL DATUM ELEMENTS

• NGVD 29 NAVD 88
• DATUM DEFINITION 26 TIDE GAUGES
  FATHERS POINT/RIMOUSKI
• 
  IN THE U.S. CANADA
  QUEBEC, CANADA
• BENCH MARKS 100,000
  450,000
• LEVELING (Km)
  102,724
  1,001,500
• GEOID FITTING Distorted to Fit
  MSL Gauges Best Continental
  Model

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Texas Height ModernizationGoals

• Re-establish NAVD 88 elevations in Texas to
  national (NGS) standards.
• Train Texas Surveyors and Engineers to establish
  elevations to NGS standards.
• Connect NAVD 88 heights to Texas Coastal Ocean
  Observation Network.
• Determining valid NAVD 88 heights for Texas CORS
  Antenna Reference Points.
• Expand the use of GPS for elevation determination.

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Texas Height ModernizationGoals

• Determine elevations for all Hurricane Evacuation
  Routes in Texas.
• Upgrade leveling software and procedures.
• Establish Texas Spatial Reference Center.
• Build an online data reference warehouse.

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Results for First Year

• Trained 520 surveyors on NGS leveling techniques.
• TSPS/TxDoT Seminars in
• Houston 371
• Arlington 48
• San Antonio 58
• Laredo 22
• Austin 20

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Results for First Year

• Let 22 field work contracts to Texas surveying
  companies for GPS leveling to NGS standards.
• 68 GPS on Benchmarks
• 68,000 private sector funding
• Results will improve GPS elevation observations

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GPS on NAVD 88 Benchmarks
Observations to TM59 standards by 22 private
surveyor contractors
To improve in the national GEOID model
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Results for First Year

• 250 kilometers of Hurricane Evacuation Route
  Surveys
• Jefferson Co. 60 km
• Calhoun/Victoria Co. 40 km
• Nueces Co. 90 km
• Cameron Co. 30 km

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Hurricane Evacuation RouteElevation Profiling

• Perform hurricane evacuation route surveys using
  the Applanix Pos-LV system.
• Applanix system allows a vehicle to log accurate
  3-D data by combining GPS inertial sensors.

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Results for First Year

• NAVD 88 elevations on four CORS sites
• Port Aransas
• Corpus Christi
• Sanderson
• Del Rio

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Texas CORS Stations
(online as of September 2006)
National CORS 60 TXDoT 3 H/G Subsidence Dist. 63
Total Co-op CORS (not plotted) 28
u
Sanderson CORS
u
Del Rio CORS
u
Corpus Christi CORS
u
Stations re-observed by Texas Height
Modernization program
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Antenna side view from site TXCC
Side view from NGS site
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Connecting Corpus Christi CORS to NGVD 88
TXCC
234.742m
CORC B
211.462m
CORC A
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Corpus Christi CORS ARP

• 17.33 m NAVD 88 ARP (old 2002)
• 17.317 m NAVD 88 ARP (new 2006)
• (to be published as 17.32 m)
• Antenna hardware changed 2003

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Results for First Year

• Software to streamline digital level observations
  designed and coded.
• Software successfully field tested.
• Results in estimated 50 increased efficiency in
  operator training time and field observation
  time.

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Software Development
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Results for First Year

• Texas Spatial Reference Center.
• Letter of direction from Governor Rick Perry to
  establish TSRC at Texas AM University-Corpus
  Christi.
• Formal request submitted to Texas AM University
  System.

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GOVERNOR PERRY DESIGNATES TEXAS AM CORPUS
CHRISTI TO HOST THE TEXAS SPATIAL REFERENCE
CENTER
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Connect Texas Elevations to Texas Coastal Ocean
Observation Network
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CORS on NOS Tide Gauge
In cooperation with Harris-Galveston Coastal
Subsidence District
Proposed Location
NOS Gauge - Galveston Pleasure Pier
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End of presentation.
Beginning of solution.
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• Thank you for listening.