Introduction to GPS/GIS

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

GPS Equipment Handheld Survey Palm

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

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)

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

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”

- +

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

Latitude-Longitude All values for longitude in the United States will be a negative number

,

,

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

Latitude-Longitude data 32º 45’ 12” x -84º 35’ 57” DD/MM/SS 32º ’ x -84º 95.00’ DD/MM.MMM º x º DD.DDDDD

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

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

Using a handheld GPS Single point to denote entire infestation Try to collect that point in the center of the infestation

Using a handheld GPS

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

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”)