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Published byLouisa Richardson Modified over 9 years ago
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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 Handheld Survey Palm
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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 (“Doug’s farm” or “Garlic Mustard #1”)
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