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Permanent GNSS/GPS Station Planning: Technology, Equipment, Costs

Permanent GNSS/GPS Station Planning: Technology, Equipment, Costs

Permanent GNSS Stations for Geodetic Applications: Equipment, Sites, Costs -- S. Fisher

This is intended as a primer for investigators wishing to implement permanent GNSS stations within their projects. A basic overview of equipment typically employed by UNAVCO investigators and site requirements is included, along with links to additional information contained on this and other web sites. We also include a summary of equipment sources and approximate costs to help with planning and budgeting of permanent stations.

For information or help, e-mail supportunavco.org.

[+] Site Characteristics

Site Foundation

  • Local geology – consider proximity to faults, landslides, subsidence areas, etc.

  • Bedrock foundation is preferred

  • Soil or alluvium options require more extensive monumentation

  • Roof tops are sometimes the only option -- near support structures on bearing wall buildings is best, if roof top location is required

Horizon mask

  • Rule of thumb: minimize obstructions above 15°

Site security, ownership and permission

  • Location must be secure and viable over long term

Multipath

  • Rule of thumb: site should be at least 15 meters from reflective sources

  • Antenna height: at ground seems good, but observed multipath high at some sites with ~.5 m height

  • Avoid creating cavity between backplane and monument top

  • Researchers are working on methods for calibrating site multipath -- one example is the AMCS project

Radio Frequency Interference (RFI)

  • Rule of thumb: site should be at least 1 km from powerful microwave sources, independent of the frequency that they operate at

Co locations with other instrumentation

  • Co-location with VLBI or SLR systems is desired at core global reference stations

    • High precision tie survey essential, but is difficult and requires specialized knowledge and capabilities – contact support@unavco.org for more information

  • Site infrastructure (site location, power and communications) can be shared with nearby seismic stations

    • Requires coordination with operator such as IRIS

Data quality assessment can be accomplished using the UNAVCO TEQC toolkit

More Information on Site Reconnaissance and Security from the UNAVCO Knowledgebase

[+] Monuments

[+] GNSS Receivers

Tracking Performance

  • General:

    • Dual frequency, many independent channels, up to 20Hz sampling, ~ 1 mm phase precision

  • GNSS observables

    • Current:

      • GPS L1 C/A, L1and L2 P, L1 and L2 phase (also under AS)

      • GLONASS L1 C/A Code, L1 P and L2 P, L1 and L2 phase

    • Coming soon:

      • GPS L2C, L5 – first launches in 2005-2007, IOC/FOC in 2012/2015

      • Galileo – IOC/FOC 2010+ (anticipated)

  • Performance measures

    • 99%+ of expected data

    • Cycle slips/observations <0.1%

    • MP1 and MP2 <0.5 m at elev. >10°

    • Zero baseline phase precision < 1 mm

    • Short baseline precision 2 mm horizontal/4 mm vertical

Features and Specifications

  • Power consumption 3-10 W

  • Memory up to many GB

  • Multiple I/O ports

    • Log and output multiple formats simultaneously

    • Raw, RINEX, BINEX, RTCM SC104, etc.

  • Command and control interface

    • Built in server technology supports http and ftp over TCP

    • Configuration over network by uploading configuration file

    • Serial commands and custom interface applications

  • Environmental specifications: -40 to +60 C, humidity sealed

  • Power management: ability to cycle power remotely and automatic restart in same configuration after power loss

  • Ability to log and stream data from external sensors (met, tilt)

  • Code and carrier multipath rejection and ability to disable

  • External timing frequency input

  • Highly reliable: Mean Time Between Failure (MTBF) ~60,000 hours

Commonly Used Models

      [+] Antennas

      • Stable, well defined phase pattern -- consistent between like models

      • Backplane that rejects multipath

      • Absolute calibrations of antenna and radome pair are now considered standard by IGS

      • Current best practice: Gold standard is still the choke ring design with D&M element, which is produced by several manufacturers, but many question whether extra cost is worth it and are going with less expensive models

      • More information on antennas available from UNAVCO

      [+] Antenna Mounts

      • Securely attach antenna to monument/tamper resistant

      • Ability to center, level and orient antenna in azimuth

      • Reduce potential for multipath by minimizing surface area (do not create resonant chamber behind antenna ground plane)

      • Current best practice: SCIGN mount or similar

      • More information on antenna mounts used by UNAVCO

      [+] Radomes

      • Material should be homogeneous and of uniform dimension

      • Hemispherical shape with center of curvature at average (absolute) L1/L2 phase center Radome should be calibrated along with antenna

      • Current best practice: Do not use radome unless required for weather, debris or vandal protection

      • If used with a choke ring antenna, UNAVCO typically uses the SCIGN tall model

      • More information on antenna radomes used by UNAVCO

      [+] Ancillary Sensors

      • Met – surface pressure and temperature at the GNSS antenna is required for water vapor applications

      • Tilt – site and monument stability, slope monitoring, volcano deformation

      • Data are typically logged within the GNSS receiver

      • More information on meteorological sensors used by UNAVCO

      [+] Power Systems

      [+] Enclosures

      [+] Data Communications

      • Communications solution depends on data requirement

      • Options range from analog modems over circuit switched (telephone) networks to broadband satellite

      • Use of public Internet is generally preferred

      • More information on data communications equipment used by UNAVCO

      • The following tables list data communications requirements for different GNSS applications and technology options to satisfy requirements

      Definition of Data Communications Requirements for Different Applications

      Level 1:
      • 15-30 second sampling, daily to hourly retrieval, many hours latency

      • Precise orbits, reference frame, tectonics, ground based PWV/climate

      Level 2:
      • 15-30 second sampling, 10-60 minute retrieval, 10-60 minute latency

      • Ground based PWV/forecasting, ionosphere, space based PWV

      Level 3:
      • 10 Hz to 1 second sampling, streamed or small batch retrieval, several minutes latency, guaranteed delivery

      • Seismology (ground shaking and large event detection), tsunami warning, photogrammetry/airborne LIDAR

      Level 4:
      • 1 second sampling, streamed retrieval, verified, few seconds latency, late data considered perishable

      • Global or regional differential surveying systems, precision navigation

      Special:
      • Broadcast via wireless link or Internet

      • RTK surveying, virtual reference stations, machine guidance and control, structural and geophysical monitoring systems

      Data Communications Technologies, Capabilities and Suitability of Use

      Service Data Rate and Suitability Approx. Cost (US) Issues or comment
      Broadband Internet 128+ kbit/s All levels $60 per month to much more, plus hardware, often access is provided at no cost by host institution Limited availability of services outside of metropolitan areas, “last mile” problem, cost varies greatly by location and service level, some providers may charge by data volume, potential security and firewall issues
      Dial-up/PPP <56 kbit/s Level 1 $30-200 per month, $100 hardware Over phone network, limited bandwidth, potentially expensive telecom service fees, line quality can be problematic
      Cellular Technologies (CDMA, CDPD, GSM) 10-300 kbit/s Level 1-3 $80 per month, $1,000 hardware for CDMA Limited coverage (especially for data services), change management, network reliability and loading, no priority access for safety of life applications, PPP services in some areas
      INMARSAT (BGAN and RBGAN) 144-384 kbit/s Level 1-4 Charged by byte, ~$150 per month for level 1-2, $1,500 hardware New service, limited coverage as service rolls out, RBGAN has latencies, BGAN allows streamed data, but with very expensive per minute fees
      IRIDIUM <2.4 kbit/s Level 1-2 $500/month at US government rate, commercial rates prohibitive,  $1,500 hardware Too expensive for all but the most remote locations where no other options exist, limited bandwidth, potentially useful for system health monitoring
      Shared VSAT Service 300-500 kbit/sLevel 1-4 $200 per month, plus $1,000 hardware Availability of local providers?  System latencies may prohibit level 4 applications
      Dedicated VSAT 64-500 kbit/s Level 1-4 $1,200 per month minimum space segment lease, $3,000 hardware plus hub Licensing, expensive space segment lease, must own and maintain receiving hub, high power consumption, latencies my prohibit level 4 applications
      Private Wireless 115 kbit/s -54 mbit/s All levels Special Costs vary substantially, WiFi - $300+, Industrial UHF - $2,000+, no airtime service fees Addresses “last mile” problem, many options exist from WiFI to industrial narrowband, GPS vendors have proprietary solutions for RTK applications

      [+] Equipment Costs and Sources for PBO Style Permanent Stations

      Item Approximate Cost

      P/N or Notes

      Source
      GNSS Receivers
      $3,400 to $12,000
      Including antenna, Price depends on model and quantity ordered, PBO standard is Trimble NetRS with Choke Ring antenna See UNAVCO Member Purchase Program for vendor contact
      Monuments
      .
      .
      .
      Short Drilled Braced Monument
      $650
      Plus required tools Various. - See UNAVCO SDB monument web page
      Deep Drilled Braced Monument
      $8,000 to $15,000
      Depending on location, specialized drill rig required Various. - See UNAVCO DDB monument web page
      Equipment Enclosure w/ DC backpanel
      $950
      .
      Various. - See UNAVCO enclosure web page
      Solar DC Power System
      .
      .
      .
      2 x ~100 Ahr Gel battery
      $250
      Alternative - DEKA/MK 12-volt, 100-AH, Gel battery, or Similar
      Alternative Solar Products, 27412 Enterprise Circle West, Suite 101 Temecula, CA  92590, Tel. 866-532-8810
      2 x 72-80 W Solar Panels
      $900
      Depending on Location

      Alternative Solar Products, 27412 Enterprise Circle West, Suite 101 Temecula, CA  92590, Tel. 866-532-8810

      or

      ETI Solar – Energy Technologies Inc. 101, 18327-105 Avenue Edmonton, AB, T5S 2K9 Canada, Tel. 780.489.3700

      Solar panel mount
      $200
      Two panel model Precision Design & Machine 6595 Odell Place, Suite F, Boulder, CO 80301, Tel. 303-527-3049, PDMachine@msn.com
      SCIGN antenna mount
      $550
      See information on UNAVCO web site

      SCEC University of Southern California 3651 Trousdale Parkway, Suite 169 Los Angeles, California, 90089-0742 John McRaney, Tel. 213-740-5842

      or

      Precision Design & Machine 6595 Odell Place, Suite F, Boulder, CO 80301 Tel. 303-527-3049

      SCIGN radome (tall model)
      $220
      See information on UNAVCO web site SCEC University of Southern California 3651 Trousdale Parkway, Suite 169 Los Angeles, California, 90089-0742 John McRaney, Tel. 213-740-5842
      Cellular Communications
      .
      .
      .
      Cellular modem
      $795
      Proxicast LAN-Cell Mobile Gateway Model 1XMG-401 - TDMA or ModelGPRS-401-GSM Proxicast 312 Sunnyfield Drive, Suite 200 Pittsburgh, PA 15116-1936 Tel. 877-777-7694
      Cellular antenna
      $50
      MaxRad WMLPVDB 800/1900

      Hutton Communications 2520 Marsh Lane, Carrollton, TX 75006 Tel. 877-648-8866

      Antenna L-Bracket
      $15
      MaxRad MMK1924 Hutton Communications 2520 Marsh Lane, Carrollton, TX 75006 Tel. 877-648-8866
      Antenna base
      $50
      MaxRad MVP Hutton Communications 2520 Marsh Lane, Carrollton, TX 75006 Tel. 877-648-8866
      Communications Service
      $60-80/month
      Verizon or Cingular depending on coverage area

      Verizon Wireless P.O. Box 4001, Inglewood, CA 90313-4001 Tel. 888-466-4646

      Cingular Wireless PO Box 30218, Los Angeles, CA 90030-0218 Tel. 800-331-0500

      Ethernet Radio
      $1100 to 1300
      Intuicom EB6 Plus - Price depends on quantity ordered, 2 or more required, includes antennas and cables, used for bridging to cellular or other internet connection See UNAVCO Member Purchase Program for vendor contact
      Misc Supplies
      .
      .
      2 x N connector for LMR 400 cable -
      $10 ea.
      EZ-400-NMH Hutton Communications, 2520 Marsh Lane, Carrollton, TX 75006, Tel. 877-648-8866
      N-type 90° connector
      $10 ea.
      EX400NMH-RA Hutton Communications, 2520 Marsh Lane, Carrollton, TX 75006, Tel. 877-648-8866
      Liquitite conduit and connectors
      $40
      .
      Graybar, Inc. 1375 W. 47th Ave., Denver, CO 80211 Tel. 303-458-7770

      [+] Data Management and Network Monitoring

      • Data Retrievals

        • Method depends on receiver type and communications

        • IP scripting for Internet capable receivers like NetRS

        • Batched and streamed protocols and data formats

      • Performance Monitoring and Verification

        • Outage notification via Internet

        • For batched retrievals, file size check before retyring

        • Verification using TEQC

        • More sophisticated approach for streamed data (RAIM or other)

        • Metrics include expected vs. observed data, cycle slips, multipath, position residuals, retreival latency

      • Data Available at Public Archives

        • UNAVCO, SOPAC, CDDIS

         

       

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      Comments (2)
      Comment by Malcolm McClure on Fri, Mar 13th, 2015 at 9:29 PM
      How do I find where the closest GNSS receiver/station is located near to Ardara, Co Donegal, Ireland?
      Comment by Apple Macbook Pro review on Sat, May 21st, 2011 at 8:04 AM
      It is really a very good knowledge based information you are sharing here with us.I really found it interesting to go through your post. <a href="http://www.notebookshopper.net/apple-macbook-pro-spring-2010.html">Apple Macbook Pro review</a>
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      Last modified: Monday, 12-May-2014 00:18:29 UTC