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Capturing data and use of GPS Capturing data GIS GPS Paper maps - - PDF document
Capturing data and use of GPS Capturing data GIS GPS Paper maps - - PDF document
Capturing data and use of GPS Capturing data GIS GPS Paper maps Coordinates Satellite images What is a GPS? Global Positioning System A network of satellites that continuosly transmit informations Making possible to identify locations How
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What is a GPS?
Global Positioning System A network of satellites that continuosly transmit informations Making possible to identify locations
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How works a GPS
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Possible sources of errors
- Getting signals from 3-4 satellites GPS calculates
its position by triangulation
- The number of satellites “in view” depends on the
time of day and where you are on earth
- Unfortunately satellites are often hidden behind
mountains, buildings and even forests
- The more satellites that can be tracked the greater
the chance of an accurate position fix.
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Sources of Errors in GPS
- Poor signal reception
can be cause by
– Blockage by buildings, hills, trees and even your own body – Weak batteries – Interference from other electronic equipment in use nearby
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This is your GPS
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Pages featured in your GPS
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Menu button
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Acquiring satellites
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Horizontal position Latitude Longitude Latitude Longitude Altitude
Acquiring satellites
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Acquiring satellites
Horizon 45° above the Horizon Overhead
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Defining your position
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Defining your position the average position
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GPS use
- The GPS gives you the possibility to define
your position with coordinates:
– Latitude – Longitude – Altitude
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The two coordinates together do the earth’s grid Latitude and Longitude are expressed in: Degrees, Minutes, Seconds
- Long. W 73° 59’ 15 ’’
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Latitude, longitude, decimal degrees
- Latitude and Longitude can be also
expressed in decimal degree
Decimal degrees = Degrees + (Minutes/60) + (Seconds/3600) 73° 59´15 ´´ = 73,9875
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Basics
Latitude: 90 North 1 Equator 90 South Longitude: 180 West Null Meridian 180 East
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To allow to pass from a curved Earth to a flat map
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Mercator projection
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Advantages of UTM
- Square grid allows easy measurement
- Cartesian coordinate system
- Metric unit
- No negative numbers
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