 |
|
We have Garmin eTrex receivers available for your use, although it is not central to our research objectives. These are rather simple devices to use, and are quite portable and durable under normal use. PLEASE LEAVE THE PROTECTIVE CASES ON EXCEPT TO CHANGE BATTERIES! The receivers are also reliable within their limitations, most notably that they have a 15 m horizontal accuracy (elevation readings are far less reliable). THE RECEIVER MUST BE IN AT LEAST 3 MPH OF MOTION FOR SEVERAL MINUTES TO PROPERLY RECORD (+ OR - 15 M ACCURACY) POSITIONS!
To start the receiver, push and hold the Power button for about two seconds (see control panel details below). Initially there is a Welcome page, then a SATELLITE screen appears showing the status of satellite signal capture. Signal capture and lock may take several minutes if there are dense clouds or foliage overhead, and probably will not capture adequate signals at all inside of buildings. Various prompts come up if the signal is unsuitable for several minutes.|
|
|
|
to Controls diagram; "Back" to return here
|
When you initially start the unit, a SATELLITE screen is in view while the receiver attempts to capture a necessary number of signals from several satellites. The outer circle represents the horizon, the inner circle is 45 degrees above the horizon, and the center of the circles is directly overhead; north here is at the top. A black square is a satellite that the receiver has locked onto; a weak satellite has no square. The histograms below the circles indicate the relative signal strengths (solid for ready, open for ephemeris still being collected). Both portrayals give the satellite ID number. Once locked, you can begin using the MAP or POINTER screens. The MAP page display shows your position relative to other nearby waypoints ("landmarks"). Pushing the Up or Down buttons enables you to change the display scale. If you push the Enter button you have various change options to this display. After making any, push Page to return to the main MAP page display. After the receiver has at least three locked satellites, Page to POINTER. It will have UTM coordinates of your current location across the bottom. The compass shows the direction towards a GOTO waypoint ("target"), and above this there is information about the distance and estimated travel time (based on your latest velocity) to the GOTO destination. Using the Enter button on this page brings up options that ordinarily we will not need; push Page to return to the main POINTER page display. The MENU page provides access to many functions. Please do NOT make any Setup changes, as these need to remain consistent between class members. [BACK] |
Use the Up or Down buttons to select MARK, then Enter to record positional information (for the location where you push it) as a "waypoint". Push Enter at the "OK?" prompt to store this waypoint, or Page to return to the MENU page. If you wish to name your waypoint, push Up then Enter to call up a scrolling alphabet selector. Use the Up or Down buttons to select letters, and the Enter button to move to the next character position. You can label (up to six characters) your waypoint this way, and then Enter when done.
Waypoints remain stored in the receiver until 1) you delete them, or 2) the batteries go dead.
If you select and Enter WAYPOINTS, you can use the Up or Down buttons to select one (or the Nearest one). BE CAREFUL NOT TO PUSH ENTER WHILE "DELETE ALL" IS THE SELECTION! Once you Enter to select a waypoint, the Up or Down buttons give you a choice of various options. Highlighting the waypoint name, then Enter, allows you to relabel that waypoint. Highlight and Enter GOTO sets that waypoint as your destination target for the MAP and POINTER displays.
We will not use the MENU page's ROUTE and TRACKS displays, as these are active navigation rather than the position data capture functions that we need for this course.
Below is the practice map and list of waypoint coordinates that we shall use to familiarize you with GPS functions here on campus.
[BACK] [TOP] 344 Calendar 358 Calendar
You
are visitor # to this Web page since
10SEP01.
N. C. Heywood maintains this page, last updated 25NOV03.
