Introduction to GPSGIS

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Introduction to GPS/GIS
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Collecting location data

• Coordinates that denote the location of an
  infestation
• Using a hand-held GPS unit
• Online method (more on this later)

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GPS Equipment
Palm
Handheld
Survey
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Coordinate Systems

• Coordinate settings
• UTM x,y, and zone
• Lat/Long x and y
• Datum
• (NAD27 and NAD83)

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UTM Coordinates

• Universal Transverse Mercator
• Originally used by US Army on large scale maps
• Grid system
• Divides the earth into 60 zones (each 6 degrees
  of longitude wide)
• X,Y system in meters east of zone line and north
  of equator (in Northern Hemisphere)

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UTM Coordinates

• Location data in a combination of X,Y and zone
• Southeast lies within Zone 16, Zone 17 and Zone 18

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Lat/Long Coordinates

• Based on degrees of a circle (360º total)
• Latitude expressed as degrees north of equator
  (Southern Hemisphere is denoted by a negative)
• Longitude expressed as degrees east of the Prime
  Meridian (west is denoted by a negative with the
  maximum value of 180º and minimum value of -180º)

Lines of Latitude
Lines of Longitude meridians
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-

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Latitude-Longitude

• Latitude
• Starts at Equator
• 90ºN and 90ºS
• U.S. 24º and 49º
• Longitude
• Starts at Prime Meridian
• 180ºE and 180ºW (denoted with a negative)
• U.S. -65º and -125º

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Latitude-Longitude

• All values for longitude in the United States
  will be a negative number

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33.75333, -86.59917
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33.75333, 86.59917
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Latitude-Longitude data

• DD/MM/SS (Degrees,minutes,seconds)
• DD/MM.MMM (Degrees, decimal minutes)
• DD.DDDDD (Decimal degrees)
• Same coordinate system, different ways of
  expressing it

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Latitude-Longitude data

• 32º 45 12 x -84º 35 57 DD/MM/SS
• 32º 45.2000 x -84º 95.00 DD/MM.MMM
• 32.75333º x -84.59917º DD.DDDDD

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Datum

• Set of surveyed points used as a reference for
  making maps
• Most USGS topographic maps used the survey points
  from 1927 (NAD27)
• Those points were re-surveyed and corrected in
  1983 (NAD83)
• WGS84 is another datum often used, essentially
  the same as NAD83

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Collecting location of an infestation

• We prefer that you use Latitude/Longitude
  expressed in Decimal degrees
• With NAD83 (or WGS84) datum
• Most GPS units have the ability to set coordinate
  system

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Using a handheld GPS

• Single point to denote entire infestation
• Try to collect that point in the center of the
  infestation

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Using a handheld GPS
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Recording point data

• Stand at, or as near as you can to, the center of
  the infestation
• Make sure the GPS is set to show lat/long data in
  decimal degrees (DD.DDD)
• Make sure datum is set to 1983 (NAD83)
• Often, the longer the GPS is stationary, the more
  accurate the point is

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Recording point data

• Either write-down the coordinates (record at
  least 5 decimal places) or create a waypoint (so
  that you can write it down later)
• Title the point something that can associate it
  with the area or invasive species (Dougs farm
  or Garlic Mustard 1)

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