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Setting Up a New Site for GPS Operations

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  1. Setting Up a New Site for GPS Operations

  2. Benefits of a well planned setup • Setting up the site right – the first time! • Reduces setup errors, which could result in rework • Reduces time wasted on multiple equipment setups and site visits • Increases productivity of machines and field crews • The project is completed faster! • You save time and make more money!

  3. Setting Up a Site for GPS -Topics • Preliminary preparation • Site reconnaissance • Setting up the site • Site Calibration • Conclusion

  4. Preliminary preparations • Digital data – What do you have? • CAD data • 3D Model • Who is responsible for control? • Owner or you? • Resources to perform in-house or contract • Trimble Connected Site preparedness • Internet connectivity (Land Line vs Cellular) • IBSS • 2-Way data

  5. Digital Data • CAD data must always be verified • CAD data often must be corrected and/or enhanced • Trimble Business Center – Heavy Construction Edition (HCE) data prep module can provide you with the tools to perform this task • You should understand the needs of office systems vs field systems and learn what formats are needed

  6. Control • What is control? • A set of points by which everything is referenced to • They should be set with a high degree of accuracy • Usually have been network adjusted (TBC Advance Survey Modules can be used for this) • Control points are measured to “calibrate” the site for GPS-based systems • You need a minimum of 3 and 5 or more are recommended • Do control points exist on site? • Check the site plans for control point lists and locations • Check with engineer

  7. Control Point Locations • 3 points • will work, but yields only 3 baselines • Geometry could be weak • Control should encompass the entire site

  8. Control Point Locations • 4 Points • Better, 6 baselines • 4th point - independent height check • Geometry is stronger

  9. Control Point Locations • Optimal control- • Multiple control points • Geometry strongest, balanced • Points encompass the site. • This example - 7 points, 18 baselines.

  10. Connected Site • Connecting your site enables • Remote transfer of designs • TCC or email - Rovers • TCC or 2-Way data - machines • Remote Productivity reporting • Work Order results from SCS900 • Productivity tag files from machine • Remote troubleshooting • Trimble Assistant • 2-Way data • RTK Correction source delivery • IBSS • VRS

  11. Connected Site Things to be aware of • Internet Connectivity • LAN – Comcast, Cox, etc. • Stable & faster transfer rate • Cellular – At&t, Verizon, T-Mobile, etc. • Peak use outages • Will you be using remote correction source? • VRS • Private or government • IBSS • Managed or Unmanaged • Remember - these are things beyond contractor control

  12. Site reconnaissance • Size, duration, and environmental considerations • Control verification • GPS base station locations • Correction source delivery

  13. Size and duration of the site • Size and duration of site dictates: • GPS base station setup • Semi-permanent installation vs daily setups? • Connectivity • Fixed GPS and radio network infrastructure • Linear versus enclosed • IBBS / Local Base • VRS (Virtual Reference Station) • Rebroadcast = GPS Base Station = Radio / Repeater

  14. Environmental considerations • Undulating versus flat terrain • Urban canyons and dense foliage • Radio Interference • Airport radio towers • Microwave towers

  15. Control • Do control points exist on site? • Check the site plans for control point lists and locations • Check with engineer • How many? You need a minimum of 3 and 5 or more are recommended • Do they provide good GPS visibility? • What is there geometry relative to the site?

  16. GPS base station - Location • Set GPS antenna with 360° view of the sky. If limited try to set up with clear visibility to the equator. • GPS 55° latitude limit • Glonass 65° latitude limit • Avoid sources of multipath • Chain link fence • Trees • Flat, reflective surfaces • Setup GPS base radio link for maximum range • Elevate the radio antenna to increase range • Correct antenna (high gain and low gain) • Avoid sources of RF interference • Microwave, radio towers • Power lines

  17. GPS base station • Accessibility • Access to where it can easily be configured, monitored, serviced, and connected to via PC • Power sources • Permanent or fixed power sources are ideal for long term projects (AC / fixed generators) • Portable power sources - Ideal for daily usage or to provide back up to fixed power (batteries, solar panels, etc) • Conditioned power is ideal to prevent power “spikes” to reduce system damage & outages • Theft and vandalism mitigation • Permanent setup - recommend a fixed, secure location • Portable setups for rapid daily use and tear down

  18. GPS base station • RTK Correction source options • Site Base corrections via radio • Semi-permanent or Portable • Local Base (over internet) • Private Permanent base • COORS • IBSS (Internet Base Station Service) • Trimble over internet solution • VRS • Rebroadcast (IBSS, Local Base, VRS) • Connecting SNB900 to Base over internet and re-transmitting over radio

  19. Setting up the site • Why do we need a base Station? • To achieve millimeter level accuracy we utilize an RTK solution. RTK navigation uses a base station receiver and mobile units • What does the base station do? • The Base Station sends it’s position & observations via radio to the Rover. • Base station data and rover data are processed together in rover receiver to produce 3D vector • Base station position + vector = rover position • Result: ALL POSITIONS @ THE ROVER (S) ARE RELATIVE TO BASE POSITION • Considerations • GPS base station types • GPS RTK Correction delivery

  20. GPS base station types • Modular – SPS852 • Smart Antenna (Mobile) – SPS882

  21. Modular GPS base station • Semi-permanent “modular” GPS base station • Installed on permanent structure for duration of construction project • Ideal for large projects, when multiple grade control and site positioning systems are in use

  22. Mobile GPS base station • “Mobile” GPS base station for daily setup • Easily setup • Portable to different sites or different locations on large site • SPS852 can also be used in this configuration • AutoBase • SPS882 & SPS852

  23. Mobile GPS base station • AutoBase Feature • SPS882 & SPS852 • 12 base location memory • 50 meter rule • AutoBase Warning – SPS852

  24. GPS RTK Delivery Method • Internal radio or External radio • 450 MHz and 900 MHz • .5W, 1.0W, 2.0W, High Power TM3/HPB/TDL • Internet Base Station(IBS) • Increased range limited to PPM error deemed acceptable • Cellular • Ethernet LAN

  25. Setting up the GPS base station • The Good…

  26. Setting up the GPS base station • The Bad & Ugly…

  27. Moving the GPS base station • Before calibration – no problem • After calibration – location requirement • Must be moved to point used in calibration or control point measured while using calibration • Same rules for calibration obtained under VRS

  28. Setting up the GPS base station • Common mistakes • Antenna height errors • Switching antennas • Changing type, APC difference • Moving base to unknown point • Moving base to point measured in different reference frame

  29. GPS site calibration • What is it… • Requirements

  30. GPS Coordinates NEE GPS site calibration • What is a site calibration? • A measurement procedure that defines the relationship between GPS coordinates and local coordinates • GPS in Latitude, Longitude, and Ellipsoid Height • Local Coordinates in Northing, Easting, Elevation (MSL) • We are pairing coordinates on a sphere surface and to those on a flat planar surface

  31. GPS site calibration • Residuals • Best effort translation between pairs (Control & WGS-84) • SCS900 has a Tolerance for Calibration • Value should be 50% of acceptable project tolerance • Tolerance used to test calibration result worst residual

  32. = GPS observation = Control Point GPS site calibration • Why is a site calibration required? • Allows GPS-based rover systems to work in your local site coordinate system • What is needed for site calibration • Onsite control base on local coordinates

  33. = GPS observation = Control Point GPS site calibration • Multi-point site calibration Requirements • Minimum of 3 (3D) control points • Recommend 5+ control points with good geometry for better results • Combination of horizontal and vertical points - Minimums • 3 horizontal control points & 3 vertical control points – or – • 1 vertical + 3 horizontal + Geoid model • Used when control exists and references a design frame

  34. GPS Site Calibration • Control point network geometry is key = Poor network geometry = Ideal network geometry • Enclose the project area with control • More control points and good network geometry can improve site calibration results and identify problems early

  35. Conclusion • In conclusion, remember the key site setup steps • Site reconnaissance • Size, duration, and environmental considerations • GPS base station location • Setting up the site • GPS base station setup • Site calibration

  36. Questions?