Garmin eTrex - Hiking GPS Receiver User manual

GPS data: ETrexQGIS 1
Collecting and
Working with
GPS Data
Created November, 2012
for use with:
Garmin eTrex, QGIS v. 1.7

GPS data: ETrexQGIS 2
Supplemental QGIS Exercise: Collecting and Working with GPS
Data
In this exercise you will learn how to collect data using an eTrex GPS unit. You will
then learn how to load data from an eTrex GPS unit into QGIS and display it on a
map. The instructions may vary slightly depending on your operating system and
hardware.
SECTION A: Collecting Data with a GPS Receiver
Introduction: What is GPS?
Step 1: Learn more about GPS and get familiar with receiver unit.
Step 2: Learn how to get a clear signal and the importance of locking onto an
adequate number of satellites.
Step 3: Understand the unit setup.
Step 4: Collect location data.
SECTION B: Displaying GPS Data on a Map
Step 1: Connect the GPS unit to your computer using the proper cables.
Step 2: Run the download program by using the properly installed plugin.
Step 3: Download your waypoints to a file and display them in a new layer.
Step 4: Examine your points along with some area background data
displayed from the internet.
Step 5: Save the data properly.

GPS data: ETrexQGIS 3
SECTION A: Collecting Data with a GPS Receiver
Introduction to GPS
GPS stands for “Global Positioning System”. It refers to a collection of 24 satellites
placed in orbit all around the earth with very precise clocks on board. By locating the
signals from at least 4 of these satellites from a point on the earth using a GPS
receiving unit, you can pinpoint your exact location at any given time.
Step 1: Familiarize yourself with the eTrex unit and turn it on.
The Up and Down buttons on the left will allow you to select options on pages
and menus, adjust the display contrast, zoom in and out on the Map Page, and
cycle through data on the Pointer Page.
The Enter button will confirm data entry and menu selections. Pressing and
holding this button activates the Mark Waypoint Page
The Page button will switch between pages and back you out of pages. If you
start to do something and don’t want to continue, you can stop by pressing this
button.
The Antenna should be kept unobstructed at all times in order to receive a clear
signal from as many satellites as possible. It is best to hold the unit at chest-
height, out in front of you so that your body does not block the signals.

GPS data: ETrexQGIS 4
This is the rear of the unit:
The unit requires 2 AA batteries to operate. A data cable will be needed in order
to transfer data to a computer after collection.
Step 2: Locate Satellites
Press the On button (on the right side of the unit). The unit will start to look for
satellites and will display the satellite acquisition page. This process normally
takes several minutes, so be patient. (The satellite signals do not go through
walls, so this cannot be done from inside a building).

GPS data: ETrexQGIS 5
For more detail on which satellites have been located, press the Enter button (on
the left of your unit) and choose Advanced Skyview:
This page will provide more information about the position of the satellites in the
sky and each one’s signal strength. It can help you identify possible obstacles
blocking the signal (such as buildings, trees, mountains, etc.) Preferably the
satellites locations will be a mix of high and low on the horizon, in several
different directions.

GPS data: ETrexQGIS 6
Once enough satellites have been located, the unit will say “Ready to Navigate”
and provide an estimate of accuracy. The exact number is not crucial, just know
that it can be influenced by a number of factors, mostly the number and location
of available satellites, and that you don’t want the number to be excessively large
(such as 100 meters or 300 feet). Also be aware that the location accuracy from
an inexpensive hand-held GPS unit is somewhat limited.
Step 3: Check the unit setup.
Press the Page button (right side of unit) several times, until you reach the Menu
page. Highlight the word Setup and press Enter.

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You will see the following screen. Note the settings. These are important to record
as part of your data collection so that when you bring the points into a GIS they can
be properly displayed. A common mistake when copying data is to leave off a
negative sign (which denotes latitude south of the equator) or to leave off too many
decimal places, if using decimal degrees (6 is desirable) or to record coordinates in
degrees-minutes-seconds and then improperly translate these into decimal degrees.
WGS 84 is the most common map datum; for most projects you will want to make
sure it is being used. It’s not likely you will want to change these settings, just make
a note of them, especially the first time you start using your GPS unit.
Step 4: Collect waypoints
Press the Page button (right side of unit) until you reach the Menu page, as
above. This time highlight the word Mark and press Enter.
You will see the following screen:
The Waypoint ID is important to note on your survey spreadsheet or data table as
this is what will link it to all information collected at that point, such as facility
Waypoint ID
Coordinates
h=hemisphere (northern or southern)
d=degrees
m=minutes
s=seconds (in this case, decimal seconds)
NOTE: other common settings for coordinate formats
include decimal degrees and decimal minutes—
hemisphere can also be denoted via a + or - sign

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name or other information. (You can highlight this number by scrolling up to it
and pressing Enter if you’d like to change it.)Then highlight the word OK (this is
the default, as shown above) and press Enter to record the point.
NOTE: You can collect your data either as a series of waypoints (most common for
health survey data collection) or as a “track”.
Continue to collect a series of waypoints while walking around to different
locations and pressing “Enter” at each location. The Map view screen will
show you your progress. Pressing the Up and Down buttons will zoom you in
and out on this screen.
Finally, turn off the unit to save batteries. (Turning off the unit will not cause
you to lose any data you have entered). You now have a data file you’ll be
able to view in QGIS, in the next section of this exercise.

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SECTION B: Displaying GPS Data on a Map
Step 1: Connect the GPS unit to your computer.
Flip up the rubber cover on the back of the GPS receiver unit near the top and
insert the data download cable. The opposite end of the cable will be a serial
connector.
Next, determine what type of input ports are available on your computer.
If you have a serial port, this is the preferred method. If you have a USB port,
you’ll need to use a USB/serial adapter cable.
Turn on the GPS unit. (Don’t worry what the screen says; you can bypass the
screen which searches for satellites at this point.)
You may get the following message, if you are trying to connect the device via
your computer’s USB port:
It’s also possible that you will need administrative privileges on your computer in
order to use the hardware. Follow the instructions in order to get the computer to
recognize the device.
Step 2: Start up QGIS on your computer and check for the GPS Tools plugin.
Double-click the QGIS icon on the desktop to start the program. Check your
plugin manager to ensure that “GPS tools” is enabled. (See graphic below. If
you need help with this step, or need to “fetch” the correct plugin from the
internet, please return to Exercise 2: Explaining plugins.The GPS tools
plugin is part of the main plugin installer that comes with version 1.7.4.)

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Step 3: Run the GPS Tools Plugin and download the points.
From the menu, select Plugins > Gps > Gps Tools.
(NOTE: If you have QGIS versions 1.6 or 1.8, the GPS tools may be in a
different menu or toolbar location.)