GPS on the Back 40: Assisting forest management with global positioning

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GPSon the Back 40Assisting forest management
with global positioning
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• GPS is a military system designed to provide
  the information necessary to determine locations
  accurately, anywhere in the world

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Global PositioningSystem (GPS)

• Continuous Position Fixes
• Worldwide Coverage
• Lat. / Long. / Elev.
• Centimeter to 5-meter (or worse)

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There are actually twoGlobal Positioning Systems

• NAVSTAR
• NAVigation System Timing And Ranging
• GLONASS
• GLObalnaya NAvigatsionnaya Sputnikovaya Sistema

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NAVSTAR GPS has 3 Segments

• Control Segment
• Space Segment
• User Segment

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Space Segment Description
24 Satellites 6 planes with 55o orbit Each plane
4 SVs 20,200 km orbit 1 revolution / 12 hrs
Very high orbit for Accuracy Coverage Survivabilit
y
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Status of Space Segment

• In development since 1973
• Block I (1978-1986)
• No signal degredation
• Block II/IIA (1989-1997)
• Signal degredation until summer 2000
• Block IIR
• Launched from Jan or July, 1997 to Nov, 2004
• Block IIR-M
• Launches began Sept. 2005
• Most recent- Dec, 2007 Operational Jan 2, 2008

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The Delta rocket launches GPS 2R-15. Credit
Boeing photo by Carleton Bailie
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Navstar Satellite Paths over Sinsinawa
1045 a.m. to 1145 a.m. Saturday, March 8, 2008
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Glonass Satellite Paths over Sinsinawa
1045 a.m. to 1145 a.m. Saturday, March 8, 2008
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Navstar Control
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User Segment (nearly everyone you can think of)
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How Accurate Is GPS?

• That depends.
• Time spent at a geographic location
• Design of receiver
• Receiver configuration settings
• Relative position of satellites
• Correction methods

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Will limit discussion to recreational grade GPS

• Because they are readily available
• Because they will allow you to do most of the
  things a private landowner might want to do.
• Because you wont have to sell 20,000 board feet
  of timber in order to buy one.

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Reasonable Accuracy Expectation for Recreational
Grade GPS

• 15 to 30 feet in unobstructed locations
• Potentially much worse under forest canopy during
  leaf-on period
• Even the most expensive GPS units wont do as
  well in forested settings as in unobstructed
  locations

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Typical Recreational Grade GPS units
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GPS alone provides some help with management
decisions

• Can be used to mark locations you wish to return
  to later
• Most GPS units will allow you to determine
  distances and areas as well.
• Useful for finding locations if coordinates are
  known

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If you want to make maps of your forest you need

• GPS receiver
• Software to download GPS points and tracks
• And convert them to useable format
• Software to process GPS data into useable maps
  (Geographic Information System software)

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Power of GIS comes from dynamic link between
spatial data (maps) and data base file
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Steps in integrating GPS GIS

• Use GIS and existing files to the extent possible
• Its easier
• Its faster

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Probable existing layers

• Aerial photos
• May be able to digitize ownership boundaries
• May be able to digitize some forest stands
• May be able to digitize farm lanes, streams,
  ponds, etc.
• Topographic maps
• Differentiate upland from bottomland
• Differentiate aspect differences
• Soils layers

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For things not visible on photos use GPS

• Gives reasonably accurate representation for
  things not visible otherwise
• Requires software to download and convert for GIS
  use
• May require some additional work once in GIS

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From the Forest to GIS

• Use GPS unit to collect data
• Use waypoint function to collect point locations
• Location of sample points
• Location of property corners, etc
• Use track function to collect data for lines or
  areas
• Lane center lines
• Forest stand boundaries, etc

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Downloading GPS Data

• Use software appropriate for your GPS
• Specify whether data is to be points, lines, or
  areas
• Download data
• Export data in a format compatible with your GIS
  software

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DNR Garmin
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Track File
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Point, Line and Area with Trimble GeoXT
(4500.00)
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If you are techno-inclined, with a little effort
and a relatively small monetary investment, you
can add some useful tools for forest management
and have some fun in the process.
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Whether youGPS
Or GIS
Have fun in the woods