Orange County Real Time Network

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Orange County Real Time Network

• OCRTN
• County of Orange, California
• Presented by Arthur R. Andrew III

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OCRTN

• OCRTN is a sub-network of California Real Time
  Network (CRTN)
• Consists of 10 CGPS-RT stations
• 9 Ashtech Z-XII3 and 1 Trimble NetRS receivers
• 10 Choke-Ring Antennas
• OCRTN was declared 100 operational at the
• February 20th, 2003.

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California Real Time Network (CRTN)

• San Diego County
• (SDCRTN) 18 CGPS-RT
• Imperial County
• (ICRTN) 5 CGPS-RT
• Orange County
• (OCRTN) 10 CGPS-RT
• Riverside County
• (RCRTN) 19 CGPS-RT
• Los Angeles County
• (LACRTN) 12 CGPS-RT
• Parkfield
• (PRTN) 14 CGPS-RT
• Central Valley
• (CVSRN) 5 CGPS-RT

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CRTN SDCRTN
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CRTN ICRTN
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CRTN RCRTN
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CRTN OCRTN
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CRTN LACRTN
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CRTN PCRTN
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CRTN CVSRN
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Northern California CGPS-RT
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OCRTN Baselines Lengths(Avg 15km or 10 miles)
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TelemetryConnections
Data streamed at 1 second using Spread Spectrum
radios (900 MHz)(very reliable with the
exception of SACY)
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BLSAStream data at 1 second rate using CDMA
modem(some latency issues)
Telemetry Connections
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Typical OCRTN Site

• Ashtech Z-XII/Micro-Z receiver w/ Choke Ring
  antenna
• FreeWave Spread Spectrum Radio w/ Yagi antenna

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Real TimeData Flow
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PC1 RTD Archive and Positioning
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PC2 RTD RTCM Server
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CRTN/OCRTN - Current RTK Solution

• Single Base Station Mode
• RTK rover picks which base station to use by
  dialing the IP and port address. This method
  allows rover to compute multiple positions from
  multiple base stations on a single point.
• Rover must have ability to control wireless modem
  (choose different port assignments)
• Nearest Base Station Mode
• Server picks the closest base station to the
  rover position. Does not have the ability to pick
  and choose different base stations.
• Rover must sends NMEA GGA autonomous position
  (latitude, longitude, height) to network software
  via Internet.
• Server streams RTCM version 2.2, message types 3,
  18, 19, and 22 from selected base station to
  rover.

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Data Streams and Epochs

• OCRTN OCS Server
• IP 206.194.127.187
• Port 8000s RTCM V2.2
• NAD83 - 1991.35 Epoch

• CRTN CSRC Server
• IP 132.239.152.74
• Port 7000s RTCM V2.2
• Port 8000s RTCM V2.3
• (V2.3 supports antenna models)
• NAD83 - 2004.0 Epoch

Differ by 1.75 NW
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RTD Server RTCM Usage
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Types of Surveys
Geomatics has 7 Leica SR530 RTK Rovers
Voodoo Stick

• Reconnaissance
• Aerial Target Control
• Landfill Quantities
• Monument Location Verification
• Construction
• GIS Inventory
• Topographic

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Monument Verification
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Aerial Control Densification
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Airport Crew
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(No Transcript)
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OCRTN RTK

• How does it work?

It works no different than standard RTK. The
standard RTK radios that are restricted by
line-of-sight are replaced with wireless data
modems that use the cellular providers cell site
network.
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Wireless Internet Modemsallows access to
Internet data (TCP/IP)

• CDMA/1XRTT - Code Division Multiple Access
• Static and Dynamic IP, uses TCP/IP
• Cost around 200 - 800 per modem
• In Orange County, Verizon and Sprint are the
  providers. Service charge is 79.99 per month,
  unlimited use.
• Operates _at_ 50 70 Kbps

• GSM/GPRS General Packet Radio Service Access
• Dynamic IP, uses TCP/IP
• Cost around 200 - 800 per modem
• In Orange County, ATT / Cingular are some of the
  the providers. Service charge is 79.99 per
  month, unlimited use.
• Operates _at_ 50 Kbps

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OCRTN Address/Ports
OCRTN IP Address 206.194.127.187 The site port
assignments are as follows 8000 Nearest Base
Station 8001 BLSA 8011 - WHYT 8002 -
CAT2 8013 - MJPK 8012 SACY 8015 - SBCC 8014
OEOC 8017 SCMS 8016 TRAK 8018
FVPK 8010 - Geodetics Smart RTCM Client
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OCRTNNetwork RTK

• How well does it work?

It works only as good as the GPS receiver youre
using works. Some receivers may do better on
longer lines. Some receivers may fix the
ambiguities (TTF) quicker than others.
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Santa Ana River EDM Baseline.ppt
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Base Station Characteristics

• Each Base Station has its own characteristics
  related to
• Geology - Subsidence
• Sky Visibility
• Obstructions

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May 2002 to Present - Horizontal Time Series
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Issues effecting RTK Heights
SACY CCCS TRAK
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CCCS
LBC1
SACY
FVPK
Long-term subsidence area
TRAK
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May 2002 to Present - Time Series
Horizontal - N
Horizontal - E
Vertical
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www.ocgeomatics
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http//sopac.ucsd.edu/projects/realtime/