Garmin Tips, Hints, Explanations, or Whatnot......
 
Contents:


Character Set for Comments
Comment Field and Date/Time
Compass
Computer to GPS Receiver

Computer Thinks GPSR is a Mouse
Creating a Waypoint
Data Fields
Dead Reckoning

Entering Strings (Names) Efficiently
Garmin Receiver Models
Garmin's Save Function
Gray Background Hides Lines
The Little Circle on Outer Circle
Map Display Options on Map76
Map Display Too Crowded

MapSource
MapSource Map Sets
Marking a Location
Memory Bar Indicator

Message Field and Date/Time
My Own Maps
My Own Points of Interest
Nearest to Pointer on 76 Series
Pre-entering Waypoints
Screen Contrast

Screen Resolution
Screen Scale
Simulator Mode
Track Logging

Track Log Hard to See
Unit to Unit Data Transfer
Waypoints, Routes, Tracks, and Maps
 


Garmin Receiver Models

The basic "eTrex" (also known as the Yellow eTrex) and its high-end version, the "Summit", are relatively similar.  The next product line released has the "click stick".  They are the "Venture", "Legend", and the "Vista".  The comments that follow that mention the eTrex series are most appropriate for these "click stick" models.  In the year 2004 Garmin released two new eTrex models called the Legend C and Vista C.  These color models are different enough from the other eTrexes that it might have been less confusing to have given them different names.  So be aware that some of the comments below about eTrex series may still apply to the Legend C and Vista C and other comments won't.  For instance the connector for power and data is different and no longer supports "RS232" serial but does support USB.

In a similar vane the new 2004 models 76C and 76CS also have firmware changes from the older 76 and 76S so some comments that apply to the older 76 series won't apply to the new series.  In other words there are more changes than just a gray scale to color screen and screen size.  The "C" stands for color.

The other new 2004 models are the 60C and 60CS.  These are very similar to the 76C and 76CS with the primary differences in the case and memory.  The 76C series have more memory, a better basemap, a different case/button style, and ready to go for "marine" use.  You can get the marine data information file from the Garmin web site and download it into the 60C.

I didn't need the marine information that came with the GPS76 and found that the eTrex Venture had more small town information than the GPS76 so I downloaded the city database for the Venture into the GPS76.

In 2005 a new hardware version of the basic yellow eTrex was released.  It's faster, has WAAS, and more memory than the original eTrex.

In 2006 Garmin introduced the "x" models.  Their advertising refers to "x-treme" but "x-tended memory" might be a more realistic way to view it.  The models are:
Legend Cx, Vista Cx, 60Cx, 60CSx, 76Cx, and 76CSx.  The 60 and 76 series (with the "x") also have SiRF III chipset, the eTrexes do NOT have that chipset.  Older receivers have on the order of two to three correlators per channel (approximately 30 give or take some).  The SiRF III has effectively about 200,000 correlators to search the code - frequency space for correlation peaks.  This makes the receiver much faster at getting a location and at finding very weak signals.  All the "x" models take a microSD memory card.



Simulator Mode

On many Garmin models when a receiver is in "Simulating GPS" mode you can change the "Speed" to a non-zero value and adjust direction to simulate movement.  On the GPS 76 series try going to the compass page and set one of the data fields to display speed.  Pushing the rocker switch up or down increases or decreases the speed by 10 mph when the receiver is configured to "statute" distance and speed.  Pushing the rocker switch left or right will rotate the compass display so you can set the direction of simulated travel.

This can be a fun experiment to try, find the coordinates of some San Francisco hotels, or possibly one of the hotels Miami has to offer, and toy around with their locations. It's one way to get a handle of what the device does.




Waypoints, Routes, Track Logs, and Maps

See  Garmin Screen Examples

For the basics see  Waypoints, Routes, and Track Logs



Marking a Location, Creating a Waypoint

Some of the models have a menu command or icon function to mark (create) a waypoint.  These models usually have another "shortcut" way of creating a waypoint given below.  To create a waypoint for your current location (of course the GPSR has to have a location fix/lock):

To enter your own waypoint with some coordinates you have, do the above to get the waypoint screen (it will display your current location coordinates), move to (select) the location field using the rocker key, "Click Stick", or the "UP" and "Down" buttons (depending on which model you have), and change the coordinates to whatever you want.

To mark a location based on the map screen:


Pre-entering Waypoints

Since it usually takes awhile to enter waypoint names, you can enter the waypoints ahead of time with the appropriate name and the coordinates at your current location.  Then when you reach the location, use the "Project Location" or "Reposition" function with a distance of zero to mark the current location.  The "Project Location" function is in the menu for the "Waypoint" screen on the GPS 76 series and the basic eTrex.  The GPS 76 series will project from the current location, "the map", or another point.  The "Reposition" function is a menu item on the "Click Stick" eTrex series.



Entering Strings Efficiently (Waypoint Names or Comments)

The GPS 76 series scrolls up and down the available character set with the rocker switch (the 12 series has a slightly different character set and behavior).  So the question is where are the halfway points for efficient character entry.  Note that "underscore" is not an actual character.

Forward from "underscore":  _ABCDEFGHIJKLMNOPQRSTUVWXYZ*+-0123456789
Backward from "underscore": _9876543210-+*ZYXWVUTSRQPONMLKJIHGFEDCBA_


So 20 forward strokes are needed to get to "T" and 20 backward strokes are needed to get to "T".

The GPS 76 series enters a default number for the waypoint name.  Unlike the 12 series this number is not cleared when the field is entered for editing.  This means starting from zero often and the other numerals in the first three positions instead of "underscore" for character entry.

Forward from "zero":  0123456789_ABCDEFGHIJKLMNOPQRSTUVWXYZ*+-
Backward from "zero": 0-+*ZYXWVUTSRQPONMLKJIHGFEDCBA_987654321


So it takes 20 forward strokes to get to "J" and 20 backward strokes to get to "J".

If you do a "rocker right" when the character position is an "underscore" then a "rocker left" the position becomes the "narrow space".  So this two-stroke sequence puts the character position into a different place in the character loop.  This can be used to enter some characters a little faster.  So using the shortcut "Underscore" to "narrow space" (Right then left):

Forward:  ><*+-0123456789_
Backward: ><*ZYXWVUTSRQPONMLKJIHGFEDCBA_


So it takes seven shortcut strokes to get to "2" and seven normal back strokes to get to "3".
And it takes 14 shortcut strokes to get to "O" and 14 normal forward strokes to get to "N".

"Underscore" is the basic character position display when the field is selected and "Enter" is pushed and before any value is entered.
"*" represents the narrow character field that is "blank".  It will be a space if other characters are entered after it.



Characters Supported in the Comment Field of the 76 Series

The GPS 76 series supports (displays) the following characters in the comment field when downloaded from the computer or entered with the rocker switch:

Between "Z" and digits:  ! " # $ & ' ( ) * + , - . /              Between digits and "A":  : ; ?

The following characters do not seem to be supported:

@ % ^ _ | ~ ` = \ [ ] { }



How to do a "Nearest to Pointer" Function on the 76 Series

When you pan the map you might be interested in getting a list of waypoints, points of interest, cities, or exits that are nearest to the location of the pointer not your current location.  When the pointer is at the desired location, push the "NAV" button, select "Go To Point", pick the appropriate type of point, and you will get a list either by "Name" or by "Nearest".  If the list is by "Name", use the "MENU" button to change to "Find Nearest".  Note that the type of points available depends on what was loaded in the receiver.  These points might be pre-loaded by the factory in the "basemap" or transferred by you from one of the MapSource products or waypoints transferred by some other program.

This function is straight forward on the eTrex Venture, Legend, and Vista.  Pan to the location with the click stick and then use the "Find" button.



Computer to GPS Receiver

The National Marine Electronics Association (NMEA) issues standards for interfacing marine electronics devices.  GPS receivers can be one of those electronic devices that support NMEA protocols.  When the GPS receiver is set to NMEA, it usually sends a "steady stream" of current position data to whatever is listening.  This is often used for real time tracking on a laptop computer running a mapping program or a handheld - Palm or Windows CE.

If you are having trouble getting your GPS receiver to communicate with your computer program that supports GPSRs try setting the GPS receiver to NMEA mode (serial data format).  When the receiver has a lock or is in simulator mode, it should send out NMEA data strings (ASCII text) which you should be able to see with a terminal program (i.e. HyperTerminal with Windows) on the computer.  The default speed is usually 4800 bps on the GPS receiver so make sure that the terminal program is set the same.  If you receive the NMEA strings then you know you have the correct port and the cable is good for sending data in at least one direction.  Sending data from a handheld to the GPS receiver may still not work because of poorly designed cables with low voltage supply handheld computers.

To transfer waypoints, routes, and tracks to a Garmin receiver, the receiver's serial data format needs to be set to "GARMIN" mode (GRMN / GRMN in a 12XL).  You usually can't set the speed for this mode in the Garmin receiver because it is fixed at 9600 bps (map and firmware transfers automatically shift to a higher speed).  The program you are using on the computer to transfer waypoints, etc. may or may not automatically set the speed when you set the GPS manufacturer to "Garmin".  So make sure the speed is also set to 9600, if it is settable by you, in the software on the computer.

You might set the "Baud Rate" in MapSource to 115,200 so that map and firmware transfers to the GPS receiver can proceed as fast as possible.  If there are errors, you might have to try a lower setting.



Computer Makes GPS Receiver the Mouse

If you have a situation where the GPS receiver must be connected to a Windows® based computer, the Plug-n-Play feature may decide that the receiver is a serial mouse.  You might be able to get around this problem by letting the operating system install a serial mouse driver for it but then disable that device. If you do have a serial mouse make sure you don't disable your mouse.

What you need to do depends on the version of Windows® you're using.  Try attaching the GPS receiver to the computer and start up the computer with the GPSR on.  When the computer detects the GPSR as a mouse, turn off or disconnect the GPSR so that you can still use your mouse with the computer.  Go to the device manager and look for a new mouse, something like "Microsoft Serial Ball Point Mouse".  Right click on it and look for a "Disable" function or "Properties" and then "Do Not Use This Device" or "Stop It" and set "Startup" to "Disabled".  Do Not uninstall.

To find the "Device Manager" try "Settings"->"Control Panel", then "Device Manager" or "System".  Another way to get to "System" can be "Right Click" on "My Computer" (desktop) and select "Properties".  On "System Properties" select "Hardware" and find "Device Manager".

See also the Microsoft Knowledge Base Article  # 283063, "Serial Device May Be Detected as a Serial Mouse in Windows 2000".



Garmin's Save Function

The "Save" function on current Garmin handhelds is something of a misnomer.  It's function is reduce (eliminate some or a lot of data) and then store.  The "Save" function may have been primarily intended for the "TracBack®" feature and not actually additional "track" storage.  In a sense it creates a type of route that is more detailed than the standard "Route".  The active route lists Turn 1, Turn 2, Turn 3, etc. instead of waypoint names since waypoints aren't involved in the TracBack of a "saved" track.  It is a blurring of the distinction between a route and a track.

The "Save" function removes many of the active track log points and throws out the date/time information.  A "save" function on other brands of GPS receivers may actually save all the data in the current track log - for instance check Lowrance (however note that Lowrance doesn't store date/time information in its track logs).  The active track is not automatically deleted.  There are some exceptions: Geko 201 and 301.  The Geko 201 and 301 retain the date/time information in the processed (saved) track logs but still reduces the number of points to a maximum of 500 (from possibly 10,000).  A short active track log of up to maybe 150 points might be "saved" without any points being removed. The etrex series, the 76 series, and the 60 series all throw out the date and time stamps when the active log is "saved" to the "saved" storage areas.

The removal of points is based on an algorithm to pick the most significant points.  It does not necessarily reduce to the maximum number of points that can be stored.  For instance an active track log of 2016 points might be reduced to 197 points even though there is storage space for 250 points (recent firmware releases have increased this to 750 points in some models).  Note that the loss of date/time stamps means the software on a computer won't be able to compute your speed for the various segments.

The new color models, Legend C, Vista C, 60C(S), 76C(S), have 20 "saved" track areas of  a maximum 500 points.  The Legend, Vista, map76, 76S have 10 "saved" track areas of a maximum 750 points.  The Venture and GPS 76, have 10 "saved" track areas of 250 points.

You do not need to "save" the track to transfer it to your computer.  The active log and the saved logs are all transferred to the computer when a "get track log" command is executed.

Transfering a track log that is longer than will fit from a computer to one of the "save track log storage areas" will result in it being truncated.  In this case the track log is not processed to reduce the number of points.



Comment or Message Field and Date/Time Stamps

If the waypoint name is a code or a shortened form of a place name, this field is handy for adding additional information about the waypoint such as the full name of the location, the elevation of a mountain peak, etc.

When you create a waypoint (mark a location) the date and time of creation is placed in the comment field.  For most models the comment field holds 16 characters.  It is 50 characters long in the Garmin V.

The eTrex line does not have the comment field that most other Garmin receivers have, so if you want a date/time stamp on your waypoints, don't get a receiver in the eTrex series.



Garmin Track Logging

Garmin handheld receivers have one track log called the "Active Log".  The Garmin receivers do not really have a save track function although that is what it is called.  The operation is a reduce and then store function.  It is used for a detailed back track route that Garmin calls "TracBack®".  It only stores the most significant points of your route.  These track storage areas are good for storing trail maps, coast lines, boundary lines, etc.  You can create the line set on the computer and send them to the receivers storage areas.  Besides the horizontal coordinates the elevation, time, and date are recorded in the track log.  The times and dates are removed when a "save" is done.  There are some exceptions: Geko 201 and 301.

With Garmin receivers, you do not need to "save" the active log to transfer it to a computer.  The active log and all the stored logs in the Garmin receivers are transferred to the computer when a track log transfer is done.

Most receivers support logging by time or distance intervals.  Garmin also has an "Auto" setting that logs a track point when you deviate from a straight line by a certain amount or speed drops to zero.  You set the offset amount from a straight-line with the interval setting values of: "Least Often", "Less Often", "Normal", "More Often", "Most Often". The "Auto" setting will probably give you the best representation of your route while using the fewest number of track points.

Older Garmin receivers, such as the 12XL, named track logs like "Track 001".  Newer Garmin receivers, such as the eTrex and 76 series, name track logs like "Active Log" or  "Active Log nnn" where "nnn" is 001, 002, 003, 004, etc.

If you want to transfer a track log from the computer to the receiver's active log space (large area - often 2047 to 10,000 points) make sure the log is named "Active Log" or  "Active Log nnn" .  For old receivers such as the 12XL, the track log will need to be named "Track nnn", where "nnn" is a sequence number:  001, 002, 003, etc.  If you want the log to go into one of the 10 storage areas, give it some other name.  The log will be truncated to fit the storage area (often 250 points).  The basic eTrex stores about 1535 track points and recent firmware releases for the GPSmap 76, 76S, Legend, and Vista store about 10,000 track points in the active log area and 750 points in the "Saved Track" area.  The storage area of the GPS 76 and eTrex Venture remains at 2047 points.

The new color models, Legend C, Vista C, 60C(S), 76C(S), have 20 "saved" track areas of  a maximum 500 points.  The Legend, Vista, map76, 76S have 10 "saved" track areas of a maximum 750 points.  The Venture and GPS 76, have 10 "saved" track areas of 250 points.

Old receivers generally only record horizontal coordinates and not the elevation (altitude).  Newer receivers record three coordinates (x, y, and z) in both the waypoint mark and the track log.  So don't expect to get a graph of the altitude if track logging is off or if you use an older receiver such as the 12XL.  So far Garmin receivers with a barometric altimeter have an altitude graph.  The other Garmin receivers usually do not have an altitude graph.

By using the "Save" function on the newer receivers, you can create a detailed route from the saved log (simplified track log) called a "TracBack®".



Garmin's Memory Bar Indicator

On newer model receivers the amount of memory used for tracks, routes, waypoints, user settings, and possibly other internal needs for items such as a TracBack® is shown in the memory bar.  The memory used for maps is not included in this display.  For map memory usage you need to keep notes from MapSource of how much memory each map set that you are downloading is going to use.  You might find that you are using up to about 6% with  nothing stored (waypoints, track logs, etc.).  This is the amount for your user settings. So far I have not found this indicator to be of any use.

The memory usage I am interested in is: tracks, waypoints, routes, and maps.  The receiver won't tell you how much space is available for waypoints or maps.  The track page will tell you the percentage used for track logging and the route page will tell you how many unused routes are left.

The older 12 series receivers gave you a count of how many waypoints were stored and how many track log points were stored so you knew exactly how many more waypoints and track points you could add.  This was great!  On the newer receivers I don't know when I'll run out of waypoint storage space.  I also only know when I'll run out of track log space within 1% but that's not so bad.



Garmin's MapSource

MapSource is a program for sending maps, tracks, waypoints, and routes to a Garmin GPS receiver.  It also gets waypoints, tracks, and routes from the receiver.  MapSource can display a background map on the computer screen.  MapSource is sold with some sort of map data and is given names such as TOPO (not to be confused with National Geographic's TOPO!!), Roads and Recreation, Metroguide, City Select, and City Navigator.  The names reflect the type of map data that is sold with the utility program.

You can have two instances of MapSource running at the same time and copy waypoints and tracks (or portions thereof) from one window to the other.  This allows you to merge portions of data from one file to another.

Maps loaded into the receiver are deleted by downloading a new set of maps.  All existing maps in the receiver are deleted except the base map which is stored in ROM.  That means you can't change the base map at all.

The receiver does not have a delete map function.  Try downloading an empty map set to the receiver.  But why do you want to do that?  MapSource version 5 may no longer allow the download of an empty map set.

You can turn off the display of specific map sets by going to the "Main Menu" on the GPSmap 76 and selecting "MapSource Info".  Note that you can load both the topographic and a Metroguide map for the same area.  Only one will be shown on the map screen.  You can see the underlying one by turning off the display of the top one.  The hierarchy of which maps are displayed may be: City Navigator/City Select, MetroGuide, Roads & Recreation, TOPO, WorldMap, and then the basemap.

You can't create a "track log" with this program for download to a receiver.  Many third party programs allow you to create a "track log" and download it to the receiver.  This allows you to create a "trail map" (track log trails or trail track logs) for display on the receiver or outline coastlines, property boundaries, etc.

The version of MapSource that you received on the CD-ROM may be so out of date that it won't work with your new GPS receiver.  You can download a newer version from Garmin's Internet site.



MapSource Map Sets

Map sets from the various MapSource products can be loaded into a Garmin mapping receiver at the same time but only one can be displayed at a time.  Otherwise you would have one mess of a display - removing conflicting data from the various sources is not something a receiver is capable of doing at this time.  The display hierarchy from highest priority to lowest is something like the following: City Navigator/City Select, MetroGuide, Roads & Recreation, TOPO, WorldMap, and then the basemap.  To view a map set of lower priority, you have to disable (turn off) the sets with higher priority.  This is done with the function "Main Menu->MapSource Info" on the GPSmap 76. On the eTrex Legend and eTrex Vista look under the Map Setup screen for the “i” button and select it.  Check the menu for the screen (button next to the “X” at the top) for quick ways to change groups of maps.



Your Own Maps and Points of Interest (POIs)

"Only" Garmin's MapSource™ can download maps to Garmin's receivers except that some people have reverse engineered Garmin's data structure and created GPS Mapper as one example.   Look for "GlobGPS", "MapDekode", and "GPSMapper" to create your own maps (a lot of work).

For GPS Mapper try:  http://www.cgpsmapper.com/  and  http://www.gpsinformation.net/gpsmapper/gpsmapper.htm
Note:  From about Sept. 20, 2003 to Oct. 6, 2003 the chrisb.org server may be down.  Try gpsmapper.keenpeople.com instead.

For MapDekode try:  http://planeta.terra.com.br/informatica/download1/dekode_contract.htm

Also check the GPS TrackMaker® site for hints on map creation using MapDekode.

"GlobGPS" helps in creating the data for GPS Mapper.  I understand that a soon to be released version will read OziExplorer's waypoint files and generate POI files.

The eTrex Venture and GPS 76 have a 1 Meg. memory area for storing "Points of Interest".  These are similar to waypoints but contain more information.  Normally, like maps, you would get Garmin's "Points of Interest" CDROM to download to the 1 Meg. storage area.  However you can create your own POIs and download them with GPS Mapper to the Garmin models that support POIs.  Note that POIs are also part of mapping receivers but are connected to the map data set.

Why would you want to do that?  Most of the receivers currently store 500 waypoints (recent firmware releases on some models have increased that limit to 1,000).  I don't know what the limit is with 1 Meg. but it might hold 10s of thousands - could also be dependent on how much information is included with each point.  I haven't tried it yet so I'll post more after I have tried it.



Garmin Screen Contrast

If you can't read the screen very well, maybe the screen contrast is set too low.

For some of the eTrex models, go to the Main Menu, select "Setup", then "Display".  Use the "Click Stick" to move to the contrast slider and then select it by pushing in the "Click Stick".  Once the contrast slider is selected, move the "Click Stick" up or down to move the slider then push the "Click Stick" in to finalize the contrast setting.

For the 76 series, push and release quickly (holding the button down will turn the unit off) the power button to bring up the contrast setting.  Then the rocker pad will move the contrast-setting bar.

For the 12XL, push the rocker pad left or right when the satellite screen is displayed.  This action will bring up the contrast slider.



MapSource TOPO Park Shading

National Forest and National Park areas are shaded green on the computer screen.  They are displayed on the receiver's screen in "light" (seems like "dark") gray making it hard to see some features that are drawn in dark gray or even black when it's only one pixel wide.  You can turn off the shading by going to Map Setup, Area Tab, and set "Zoom" for "Park" to "OFF".  This applies (more or less similar commands/placement) to the 12Map, V, and GPSmap 76 type grayscale mapping receivers. If you are in a park type area (national forest) the gray background should disappear making it easier to read other items on the display.

Apparently there is no way to turn it off on the eTrex Legend and Vista.



Map Display Too Crowded?

The map display has detail level settings of "Most", "More", "Normal", "Less", and "Least".  Look for it under the menus for the map display.  Also the display of some features can be turned off or the level they are shown at changed.  For those features that have a zoom level setting, the feature will be displayed at the zoom level set and below (closer).  If the zoom level is set to "Auto", it is displayed when "Garmin" thinks is best.  The eTrex Legend has a much smaller option set than the GPSmap 76.


The GPSmap 76's (not 76S) "Map Setup" has the following tabs and settings:

General
    Detail: Least, Less, Normal, More, Most
    Orientation: North up, Track up, Course up
    Colors: Land, Water
    Auto Zoom:  Set On/Off

Map
    Basemap:  Set On/Off
    MapSource:  Set On/Off
    Lat Lon Grid: Set Zoom Level including Off
    Grid Labels: Set Zoom Level including Off

Waypoint
    Waypoints: Set Text Size or Off and Zoom Level including Off
    Active Route Waypoint: Set Text Size or Off and Zoom Level including Off

Point
    Points of Interest: Set Text Size or Off and Zoom Level including Off
    Geo: Set Text Size or Off and Zoom Level including Off
    Exit: Set Text Size or Off and Zoom Level including Off

Marine
    Spot Soundings: Set Text Size or Off
    Navaids: Set Text Size or Off and Zoom Level including Off
    Tide Stations: Set Text Size or Off and Zoom Level including Off
    Services: Set Text Size or Off and Zoom Level including Off

Line
    Track Log: Set Zoom Level including Off
    Saved Tracks: Set Zoom Level including Off
    Course Lines: Set Zoom Level including Off
    Bearing Line: Set Zoom Level including Off

Area
    River/Lake: Set Text Size or Off and Zoom Level including Off
    Park: Set Text Size or Off and Zoom Level including Off
    Other: Set Text Size or Off and Zoom Level including Off
    Metro: Set Zoom Level including Off

Topo
    Major Contour: Set Text Size or Off and Zoom Level including Off
    Inter Contour: Set Text Size or Off and Zoom Level including Off
    Minor Contour: Set Text Size or Off and Zoom Level including Off
    Land Cover: Set Zoom Level including Off

City
    Large City: Set Text Size or Off and Zoom Level including Off
    Medium City: Set Text Size or Off and Zoom Level including Off
    Small City: Set Text Size or Off and Zoom Level including Off
    Small Town: Set Text Size or Off and Zoom Level including Off

Road
    Freeway: Set Zoom Level including Off
    Highway: Set Zoom Level including Off
    Local Road: Set Zoom Level including Off
    Local Road Name: Set Text Size or Off and Zoom Level including Off

Other
    Railroad: Set Text Size or Off and Zoom Level including Off
    Accuracy Circle: Set On/Off
    Heading Line: Set On/Off
    Lock to Roads:  Set On/Off

Text sizes are "Small", "Med", and "Large"; zoom levels are "Off", "Auto", and all the
map scale levels.



Dead Reckoning / Satellite Tracking Loss

Most Garmin receivers have a 30 second dead reckoning feature.  If you enter a tunnel or put your hand over the antenna (to block all satellites) the receiver will assume you are traveling in the same direction and at the same speed as you were before reception was lost for 30 seconds.  Then it will report loss of lock.


If all satellites are not lost you may have the situation where only three satellites are being tracked (or four in some configurations) resulting in a 2D location fix.  The last valid elevation will be assumed - not so bad if you are traveling on a flat road or trail. If your elevation has changed and you know the correct value you can enter that elevation for a more accurate location reading.  Look for "New Elevation" in the menu for the "Satellite Screen" on newer Garmin receivers.  It will probably be grayed out (unavailable) for a 3D fix but a darker color (available) when you have a 2D fix or worse.  However on GPS 76 series I have found they don't always "accept" the elevation I enter.  If the last elevation is say 8800 ft. and I enter the correct value of 8600 ft., the value displayed may stay at 8800 or change to something in between such as 8700 ft.



Garmin GPSR  to Garmin GPSR Data Transfer

Older Garmin handheld GPS receivers, such as the 12XL, had "Send" and "Receive" commands to transfer waypoints, routes, tracks, etc. between the units.  Newer model receivers, such as the eTrex and 76 series, do not have these commands.  The newer receivers also have newer data packet structures to support the longer waypoint names, etc. and track logs are named differently, "Active Log" instead of "Track 001".  If the new unit receives a track log that is not named "Active Log" (or Active Log nnn), that track log is sent to one of the saved track storage areas and truncated to fit.

This generally means that you can send some data (waypoints especially) from the older unit to the newer unit because the newer units understand the older data structures. However if the older unit requests data from the newer unit, the newer unit sends it in a data structure that the older unit doesn't understand.

For additional information:

"Notes on GPSR to GPSR Data Transfer"



Garmin Screen Resolutions

  Screen Size in Pixels Length of Scale Physical Screen Size
GPS 76C:
160 x 240 pixels (color)
33 pixels
1.44 x 2.19 inches
Venture: 160 x 288 pixels 33 pixels 1.1 x 2.1 inches
GPS 76: 180 x 240 pixels 46 pixels 1.6 x 2.2 inches
12XL: 64 x 100 pixels   1.5 x 2.2 inches
These are approximate values based on the scale's center of vertical to center of vertical.....
(Length of scale minus 1 pixel)
GPS 76C's Scale Feet per Pixel
GPS 76C's Scale Feet per Pixel
20 feet .63

300 feet 9.38
30 feet .94

500 feet
15.63
50 feet 1.56

800 feet
25.0
80 feet 2.5

0.2 mi
33.0
120 feet 3.75

0.3 mi
49.5
200 feet 6.25

0.5 mi
82.5





GPS 76's Scale Feet per Pixel   GPS 76's Scale Feet per Pixel
20 feet .4   300 feet 6.7
30 feet .7   500 feet 11.1
50 feet 1.1   800 feet 17.8
80 feet 1.8   .2 mi  23.5
120 feet 2.7   .3 mi  35.2
200 feet 4.4   .5 mi  58.7
         
Venture's Scale Feet per Pixel   Venture's Scale Feet per Pixel
20 feet .6   300 feet 9.4
30 feet .9   500 feet 15.6
50 feet 1.6   800 feet 25.0
80 feet 2.5   .2 mi  33.0
120 feet 3.8   .3 mi  49.5
200 feet 6.3   .5 mi  82.5
12XL's Scale (Screen Width) Feet per Pixel
.2 mi 16.5
.3 mi 24.8
 .5 mi  41.25
The current location arrow on the GPS 76C is 11 pixels wide by 16 pixels high.  At a zoom level of 120 ft. the arrow is about  41.25 ft. by 60 ft.

The current location arrow on the GPS 76 is 11 pixels wide by 17 pixels high.  At a zoom level of 120 ft. the arrow is about  29 ft. by 45 ft.



Garmin Data Fields

The most of the data fields on various screens can be set to display the following types of data:

GPS 76 and GPSmap 76 Version 2.08:
 
Accuracy ETA at Destination Speed Overall Avg. Speed (Total)
Bearing ETA at Next Time of Day Trip Time - Total
Course Maximum Speed Time to Destination Turn
Depth Moving Avg. Speed Time to Next Velocity Made Good
Distance to Destination Trip Time - Moving To Course Water Speed
Distance to Next Off Course Track Water Temp
Elevation Pointer Trip Odometer  

Venture Version 2.31 (and probably other "Click Stick" eTrexes except for additional fields for those with additional functions such as the Vista.):
 
Bearing Elevation Maximum Speed Trip Time - Stopped
Course Final Destination Moving Avg. Speed Trip Time - Total
Off Course Final Distance Overall Avg. Speed Time of Day
To Course Final ETA Odometer Turn
Current Destination Final ETE Sunrise Velocity Made Good
Current Distance Heading Sunset Vertical Speed
Current ETA Pointer Trip Odometer  
Current ETE Speed Trip Time - Moving  



The Compass

The compass takes a fair amount of power on the sensor (S) models.  It can be toggled ON/OFF by holding down the "Page" key.  Leave it off when you don't need it to save batteries.


For the compass to work, the 76S, 76CS, and 60CS need to be held horizontally (a bubble level could help).  For the GPS receiver to work well, these receivers need to be held vertically.

Note that the accuracy specification is typically 2 degrees with proper calibration and 5 degrees at extreme northern and southern latitudes.  Many non-electronic compasses are better than this and don't need batteries to work.

Apparently the new "X" series (60CSx and 76CSx) have newer magnetic sensors that are more efficient so that leaving the compass ON won't have a large impact on battery life.



The Little Circle

Some pages such as the satellite page have a circular display that can be set to either display your direction of travel at the top (track up) or display north up.  If it is set to display north up then your direction of travel will be indicated by a small circle on top of the large outer circle.


 
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