Practical applications for environment and agriculture in rural africa
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Practical Applications for Environment and Agriculture in Rural Africa. Session 4: GNSS implementation and uses in agriculture and environment United Nations/Zambia/ESA Regional Workshop on the Applications of Global Navigation Satellite System Technologies in Sub-Saharan Africa

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Practical Applications for Environment and Agriculture in Rural Africa

Session 4: GNSS implementation and uses in agriculture and environment

United Nations/Zambia/ESA Regional Workshop on

the Applications of Global Navigation Satellite System Technologies

in Sub-Saharan Africa

26 June 2006, Lusaka, Zambia

Presented on behalf of :

Dave Doyle, Chief Geodetic Surveyor

DOC National Oceanic and Atmospheric Administration, National Ocean Service

National Geodetic Survey


Michael Rasher, National GPS CoordinatorUSDA Natural Resources Conservation Service

National Cartography & Geospatial Centerby

Ken Alexander

Senior AdvisorNational Space-Based PNT Coordination Office

Geodetic Control

  • Network of monumented points

  • Precisely measured in accordance with standard procedures

  • Meets accuracy specifications

  • Adjusted to tie together and documented for multiple uses

Stainless steel rod

driven to refusal

Poured in place

concrete post

Spatial Data Accuracy

  • Accuracy crucial to building useful Geodetic Information Systems (GISs)

  • GIS builders and users must understand:

    • Impact of data accuracy

    • Details of spatial data accuracy

    • Spatial data accuracy needs

  • Surveying and mapping professionals should:

    • Understand accuracy needs of users

    • Be involved in data design and collection

 2000

Why High Accuracy

  • Realistic, useable representation of data

    • For local government, facilities management, utility and other applications

  • Large scale applications can be conducted

  • Maps and decision making information reliable

  • Data can be aligned and easily integrated

  • Survey data and GPS data can be input directly

  • High accuracy data saves expense for many operations

 2000

Misperceptions about Accuracy

  • Assumptions:

    • It will take care of itself

    • We’ll work on it later

    • The maps look good

    • The maps look accurate

    • We don’t really need that much accuracy

    • What we have is good enough

    • Just load whatever data we can get

    • It’s too expensive

  • Too little attention and understanding

 2000

Results of Inadequate Data Accuracy

  • Data mismatches, inconsistencies, lack of registration

  • Confusion

  • Battling basemaps

  • Wasted resources

  • Decisions based on “bad” data

  • Decisions based on in appropriate data

  • Lawsuits

  • Failed projects

 2000

Autonomous Positioning: Before May 1, 2000

  • L1C/A Code

  • Selective Availability On

25 - 100 m

Worst Case Horizontal 100 m

1996 Federal Radionavigation Plan

Section A2-1, Part B

Standalone Positioning Today

  • L1C/A Code

  • No Selective Availability

  • Accuracy Improvement Initiative

~ 4 - 6 m

Unaugmented Positioning: next decade

Improved resistance to interference and availability

~ 1 – 3 m

Standalone GPS, Galileo, GLONASS

Combined constellations to provide modest accuracy improvements?

Achieving Accurate GIS

  • GIS needs: resource (survey) grade GPS

    • Accuracy ~ one foot

  • GPS data can be used to adjust other data

    • Can be used for survey control

  • GPS = Accuracy

Resource grade GPS Positioning:

~ 1 foot

Large Area High Accuracy Differential Reference System

  • ACCURATE: cm accuracy on a global scale

  • MULTIPURPOSE: Best Support for: Geodesy, Geophysics, Surveying, Navigation, Mapping, Charting and other GIS activities

  • ACTIVE: Accessible through Continuously Operating Reference Stations (CORS) and other post processed (derived) products

  • INTEGRATED -- Support International services and standards (e.g. International Earth Rotation Service, International GPS Service etc.)

Continuously Operating Reference Stations (CORS)

Installed and operated by diverse, Federal, State, International and local Agencies

  • NOAA/National Geodetic Survey

  • NOAA/OAR Forecast Systems Lab

  • U.S. Coast Guard - DGPS/NDGPS

  • Corps of Engineers - DGPS

  • FAA - WAAS/LAAS (Future)

  • State DOTs

  • County and City

  • Academia

  • Private Companies

Continuously Operating Reference Stations (CORS)

  • Variety of “Geodetic Quality” Dual-Frequency

  • Receivers and Antennas are available

  • Manufacturers include:

  • Allen-Osborne



  • Trimble

CORS Requirements

  • Receiver/Antenna at least dual frequency (L1 and L2)

  • Very stable mounting

  • Reliable power available

  • Provider has on-site Internet access

  • Secured location

  • Approximate cost ~ $30 – 50k each

Continuously Operating Reference Stations (CORS)

  • International Terrestrial Reference Plane Coordinates

  • Network data collection - Hourly & Daily

  • Daily 3D Network Integrity Adjustment

  • Public Data Distribution - Internet

  • (

  • 11 Year

  • NGS Provides:

  • Global On-Line Data Holding

International GNSS Service

Tracking Network

Not Operational

What is OPUS?

  • NGS On-Line Positioning User Service

  • Processes GPS data

  • Global availability (masked)

  • 3 goals:

    • Simplicity

    • Consistency

    • Reliability

You’ve got mail!

OPUS solution

Unaugmented GPS for Agriculture and Environment

Locating and Recording Natural and Cultural Features for Local and Regional Planning

Village in Ghana

Wild Fruit Burkina Faso

Processing Mango Guinea

Food Security and Reforestation

Improved Granary Uganda

Children Planting Trees Ghana

Purifying Water Cameroon

Pond Construction Cameroon

Developing, Protecting, and Ensuring Water Supplies

Solar Panels for Water Pumps Niger

Dam ImprovementMadagascar

Preparing, Monitoring, and Managing Wildfires

Protecting and Managing Wildlife and Habitats

“We must feed our people, have safe drinking water, treat the ill ...transportation, exports and other things will come in time. “

Global Positioning System

Practical Applications for Agriculture and Environment in Rural Africa

At the end of the Day…

Change can occur with GPS

Sunset in Zambia

Ken Alexander, Senior Advisor

National Space-Based PNT Coordination Office

Herbert C. Hoover Bldg., Rm. 6822

1401 Constitution Avenue, NW

Washington, D.C. 20230

Ph: (202) 482-5809

Fax: (202) 482-4429

Presentation available:

Contact Information


How Does OPUS Work?

NGS-PAGES software used

3 “best” CORS selected3 separate baselines computed3 separate positions averaged

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