The Official Website of the Office of Geographic and Environmental Information (MassGIS)

 
  Massachusetts Geographic Information Council (MGIC)
 
October 6, 1998 - Boston, MA

"GPS APPLICATIONS FOR MUNICIPAL GIS"

The following sections provide brief summaries, in outline form, of the main points presented by the listed speakers at the October 6, 1998 meeting of the Massachusetts Geographic Information Council (MGIC). 

Moderator - Jerrard Whitten, of Merrimack Valley Planning Commission


Overview of the Topic by Jerrard, Whitten, Merrimack Valley Planning Commission

What is GPS?

  • A constellation of satellites providing world-wide positionally accurate coordinates
    • Developed and maintained by Department of Defense
    • Congress sold on the idea that other applications would follow
Space Segment Description
  • 25 Satellites
    • 6 planes with 55° rotation
    • Each plane has 4 or 5 satellites
    • 20,200 km (12,600 mi) orbit
    • 1 revolution every 12 hours
  • Very High Orbit For:
    • Accuracy
    • Survivability
    • Coverage
Why We Use GPS for Mapping
  • Line of sight
  • Data Flow
    • Data Capture
    - GPS    		 ----------------->
    <-----------------    		 GIS or CAD Systems
  • Data acquisition
Multiple Applications:
  • GIS Data Capture
  • Control Point Generation
  • Infrastructure Mapping
  • Trail Mapping
  • Vehicle Tracking
  • Marine/ Vehicle Navigation
  • Surveying
  • Emergency Services Aviation
  • Precise Positioning
  • Agriculture
  • Photogrammetry
  • Recreation (hiking etc.)
  • Many more…. and more to come

Contact Information:
MVPC
160 Main Street
Haverhill, MA 01830
Phone: (978) 374-0519

Presentation by Alex Abbott and Steven Petrecca, GIS Analysts for the Town of Brookline
"Brookline Traffic Signal Project - Municipal GPS in Action"

Alex and Steven discussed the implementation and use of GPS technology within the community of Brookline. The discussion included a brief background of Brookline's GIS and then focused on the use of GPS for municipal-wide data development projects. Specifically, the presentation included: selection of GPS for data collection, creation of a data dictionary, quality control methods, and final data implementation 


Brookline’s GPS Equipment
  • Hardware
    • Trimble Pro-XR Differential GPS
      • TDC1 Data Logger
      • Differential Beacon Receiver
      • Antenna, antenna mast, lumbar pack, etc.
    • Laser Technology Criterion 300 Laser Survey Instrument
  • Software
    • Trimble Pathfinder Office - for GPS data management


      • * Brookline’s GIS program uses both ARC/Info 7.0 and ArcView 3.0 primarily on a Sun Ultra 60 with Digital UNIX 5.6Project Design

  • Scope
    • What type of data are we planning to collect, and is GPS the best tool?
      • Points or Lines Features?
        • Points -- Traffic Signal Poles
      • Data available elsewhere?
        • No
    • How will the data be used?
      • Dept. of Public Works maintenance and complaint tracking
  • Limitations
    • Are there physical limitations which might inhibit GPS reception or use?
      • Satellite availability? Check Quick Plan to schedule
      • Tall buildings, or other obstructions? Many buildings!
      • Oncoming traffic Yes -- Beware!
  • Data Dictionary
    • How many point features do we think there are to collect?
      • 200
    • How many attributes does each point possess?
      • Intersection Number
      • Pole Number
      • Signal Type
      • Pole Type
    • What values are possible for each attribute?
      • Intersection Number 1, 1A, 2, 3, . . . 18, 19-1, 19-2, . . . 20, . . . 53
      • Pole Number 1, 2, 3, 4, . . .
      • Signal Type Vehicle, Pedestrian, or Both
      • Pole Type Pole or Mast
    • What type of data entry will we use for each attribute?
      • Menu Signal Type & Pole Type
      • Numeric Pole Number
      • Text Intersection Number
      • Date
      • Time
      • File Name
      • Separator
    • Remember -- think carefully about what data needs to be collected, but especially what data needs to be collected in the field -- it is easier to enter data on a PC than the Data Logger
    • Build Data Dictionary & Download to Data Logger
    • Conduct Field Test to verify efficiency of data structure
    • Edit Data Dictionary as needed and Download to Data Logger
Daily Preparation
  • Scheduling Data Collection - Use Quick Plan (a module within Pathfinder Office) to check on times of best satellite availability, and thus, most accurate positioning
  • Preparing Equipment
    • Beacon Receiver Batteries Charged?
    • Data Logger Batteries Adequate?
    • Laser Unit Battery Charged?
    • Memory Available in Data Logger?
Data Collection
  • GPS Cautions
    • Beware tall buildings!
    • Go slowly & carefully to avoid collecting positions which will be difficult to identify later
    • Know that you may well lose your RTCM Beacon Signal and enough satellites to raise your PDOP too high, either of which will stop new positions from being added -- Be Patient!
  • Laser Cautions
    • Beware magnetic interference which causes unpredictable errors! (Manhole covers, catchbasin grates, cars, streetlights, etc.)
Data Transfer
  • Download Data to PC
  • Review & Edit GPS Points
    • Remove duplicates & check coding
  • Export File in ARC/Info or ArcView Format
  • FTP Resulting Files to UNIX Server as needed
Quality Control
  • Display & Edit Data
    • ARC/Info Users
      • Generate coverage by running AML file created by Pathfinder Office Export Utility
      • OR use SHAPEARC command to convert shapefile created by Pathfinder Office Export Utility
    • ArcView Users
      • Add new shapefile as theme to project
  • Check all points for locational accuracy / suitability
  • Check codes
  • Collect missed points
  • Plot paper maps of all points
  • Verify all point locations
  • Request independent review of all points and associated codes

    • Re-check, Re-Check, RE-CHECK that data!

Contact Information:
Alex Abbott and Steven Petrecca
Town of Brookline
Information Services
333 Washington Street
Brookline, MA  02146
Phone: (617) 264-6487
Fax: (617) 739-7571
E-mail (Alex): Alex_abbott@brookline.mec.edu
E-mail (Steve): Steve_petrecca@brookline.mec.edu
Web site: http://www.town.brookline.ma.us/Departments/gis/

Presentation by Curtis Crow, State Geodetic Advisor to Massachusetts and New Hampshire, National Geodetic Survey
"Geodetic Control Across Massachusetts"

Mr. Crow provided an overview of GPS and geodetic control across the Commonwealth of Massachusetts. Availability and appropriate use of statewide "control points" were reviewed as well as future efforts to develop additional monumentation within the state.  Mr. Crow also addressed the status of the Coast Guard's DGPS broadcast system and the relationship of these CORS stations to the Commonwealth's monumentation.  Contact information for additional GPS-related resources also were provided. 


National Geodetic Survey
  • Founded in 1807 as the Survey of the Coast
  • renamed:
    • The Coast Survey in 1836
    • The Coast and Geodetic Survey in 1878
    • The National Ocean Service in 1970
    • NGS is the Geodetic Component of NOS
Geodetic Control
  • Network of Monumented Points
  • Precisely Measured in Accordance with Standard Procedures
  • Meet Accuracy Specifications
  • Adjusted to Tie Together
  • Documented for Multiple Use
The Ellipsoid
 
a = Semi major axis
b = Semi minor axis
f = (a-b)/a = Flattening

The Geoid and Two Ellipsoids
 

National Reference System (NRS)
Traditionally:

  • Horizontal, Two-Dimensional Positions
  • Latitude and Longitude
  • State Plane Coordinates
or
  • Vertical, One-Dimensional Elevation
  • Height above a Datum
  • (Mean Sea Level)
Monumented Points from the two systems seldom coincided 

National Spatial Reference System (NSRS)

  • Three-Dimensional Control to support Satellite Surveying Techniques
    • The Federal Base Network (FBN)
    • The Cooperative Base Network (CBN)
    • The User Densification Network (UDN)
  • Continuously Operating Reference Stations
  • A High Accuracy Geoid Model (GEOID96)
National Spatial Reference System
  • The National Spatial Reference System (NSRS) is the name given to All Geodetic Control contained in the National Geodetic Survey (NGS) Data Base.  This includes:  A, B, First, Second and Third-Order Horizontal and Vertical Control, Geoid Models such as GEOID96, Precise GPS Orbits and Continuously Operating Reference Stations (CORS), observed by NGS as well as data submitted by other Federal, State, and Local Agencies, Academic Institutions and the Private Sector
National Spatial Reference System
  • Vertical Datum Definitions:
    • Mean Sea Level Datum of 1929
    • National Geodetic Vertical Datum of 1929
    • North American Vertical Datum of 1988
  • Horizontal Datum Definitions
    • North American Datum of 1927
    • Old Hawaiian Datum
    • Puerto Rico Datum
    • St. George Island - Alaska
    • St. Lawrence Island - Alaska
    • St. Paul Island - Alaska
    • American Samoa 1962
    • Guam 1963
    • North American Datum of 1983
NAD27 vs. NAD83
  • Many Existing Maps and Older Databases are based on NAD27
  • All New Federal Maps and Most New GIS will be based on NAD83
  • GPS ‘Works’ on the NAD83
NAD 83 Network Problems
  • Not “Gpsable”
  • Poor Station Accessibility
  • Irregularly Spaced
  • Positional Accuracy
The NAD83 Adjustments
  • The initial NAD83 Adjustment did not have the benefit of GPS observations
  • GPS highlighted deficiencies in the Network
  • NAD83 readjusted following 1992 HARN observations in the Northeast
  • 1996 Observations tied HARN to CORS
  • Each Adjustment Refined Coordinates
  • NAD83(96) brings monumented Control Points onto same Datum/Epoch as Broadcast by Coast Guard from CORS Sites
  • Magnitude of Coordinate Change is Smaller with each Adjustment
 High Accuracy Reference Networks (HARNS)
  • “GPSable”
    • Clear Horizons for Satellite Signal Acquisition
  • Easy Accessibility
    • Few Special Vehicle or Property Entrance Requirements
  • Regularly Spaced
    • Always Within 20-100 Km
  • High Horizontal Accuracy
    • A-Order (5 Mm + 1:10,000,000)
    • B-Order (8Mm + 1:1,000,000)
Continuously Operating Reference Stations (CORS)
  • Permanent GPS Receiver with a Computer and Telecommunication System
  • Correlated with nearby FBN/CBN Station
  • Coast Guard and FAA Sites broadcast correctors for Meter-Level GPS Applications
  • Carrier-Phase Data posted on Internet for Higher Accuracy Applications
  • Installed and operated by various Federal-State-Local agencies
    • National Geodetic Survey
    • U.S. Coast Guard
    • Corps of Engineers
    • Forecast Systems Lab
    • Academia
    • Federal Aviation Administration -Future
    • State Dots
    • County and City
  • NGS Provides
    • Reference Site Survey Monumentation
    • Horizontal and Vertical NSRS Connections
    • Network Data Collection - Hourly
    • Daily Network 3D Validation Adjustment
    • Public Data Distribution - Internet
    • 31 Day on-Line Data Holding
    • Contact: Mr. James Drosdak
    • jimd@ngs.noaa.gov, (301) 713-3208
GEOID96
  • A Mathematical Model Relating Earth-Centered Ellipsoid Heights from GPS to Gravity Based Orthometric Heights (NAVD88)
  • Accurate to within 3 cm
Plane Coordinate Systems
  • State Plane and Universal Transverse Mercator Grid Coordinates are a direct mathematical conversion from Latitude and Longitude to a Cartesian Northing and Easting (Y & X) Coordinate System.
  • Plane Coordinates must maintain the same Datum Tag [e.g. NAD 83(1993)] as the Latitude and Longitude.
Data From NGS
  • Geodetic Control in the National Data Base is issued in 15 month intervals on CD-Rom
  • Control Data Sheets are available from the NGS Web Site: www.ngs.noaa.gov
  • CORS and Precise GPS Orbit Data is also available from the NGS Web Site
National Geodetic Survey Data From Mass Highway
  • Data not in the NGS Data Base is available from Mass Highway’s Survey Section
  • Fax a Request Letter and Map of area where Control is required to 617-973-7065 (a nominal fee will be charged to non-state agencies)
  • Questions and special requests should by directed to 617-973-7483
Interesting Web Sites
GIS/GPS/RS Web Forum: http://www.ggrweb.com/webbbs.html
The On-Line Resource for Professional Land Surveyors: http://rpls.com


Contact Information:
Curtis Crow
Massachusetts Geodetic Advisor
National Geodetic Survey
Massachusetts Highway Department
10 Park Plaza
Boston, MA  02116
Phone: 617 973 8466
E-mail: clcrow@aol.com

Presentation by Jim Bosworth, Maine Technical Source/Trimble
"The GPS Future ..."

Mr. Bosworth presented the audience with examples of new GIS applications utilizing GPS technology.  Topics covered included the use of GPS technology for emergency dispatching, intelligent transportation systems, and surveying.  The meeting concluded with a summary of technological developments that are anticipated from the GPS industry in the coming months and years. 

Short Term Advances in Hardware

  • Size  (PCMCIA card receivers)
  • Inclusive Components (Antenna/Receiver, Radios, Beacons)
  • Faster Processing (Geoid Modeling in field)
  • Lower Battery Consumption
Advances in Software/Firmware
  • Increased Accuracy via Software (GIS and Survey)
    • Multipath Reduction
    • Reduce “Noise”
    • Faster Processing in Field
      • Differential Correction (USCG, Base Station)
      • Geoid Modeling
GPS Future System Upgrades
  • Scheduled Enhancements
Funded Updates
  • Full Constellation of 24 Satellites (27 existing)
    • Funded Maintenance thru  2008
  • Removal of Selective Availability - 2000
  • Addition of L2 Civil Frequency and L3 Frequency - 2005
  • Addition of GWEN Sites -2003
Addition of 2nd & 3rd Civilian Frequencies
  • “On The Fly” Integer Ambiguity
    • Single Receiver cm Accuracy in Seconds…
    • Eliminates Base & Radios
    • True One Person
Addition of GWEN DGPS Sites
  • Ground Wave Emergency Network
  • Federal Railway Funding
  • US Continental DGPS Coverage
  • CORS Sites
  • Fort Edwards-Sarasota Springs, NY - 6/99
GLONASS
  • Down to 14 Satellites, 12 by end 98’, & 5 by end of 99
  • Russia no Funding
  • Low Maintenance, Not  Reliable
  • European Funding $
Future Applications
  • Infinite Possibilities
  • One Person Mapping/Surveying
  • Telecommunications
  • 911 Emergency Response
  • Vehicle Tracking/Scheduling
  • Timing (Cesium Clocks)

Contact Information:
Jim Bosworth
Maine Technical Source
110 Winn Street
Woburn, MA 01801
Phone: (781) 932-8888 or 1-800-332-1599
Fax: (781) 932-0450
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