A GPS User Manual: Working with Simulation Mode

Many new users of Garmin receivers have questions about simulation mode on their new units. Once they have worked through the getting started portion of the manual the wonder if they would ever want to use simulation mode again. This chapter explains what can be done with this useful feature.

Note that this mode is not always called simulation mode on the different models. On the etrex it is called "demo mode" or "gps off" while the emap calls it "Use Indoors" on the local menu or "gps off" on the setup menu.

On most units you can turn on simulation mode from the main menu. This is done by selecting "System Setup" and toggle the mode entry from "normal" or "battery/power save" to "simulation" mode. Some units have "system setup" as a submenu choice of "setup". On the G-III family and some etrex models this is also available from the local menu on the satellite status page. This information is only remembered for this power on cycle and the unit will revert to its previous mode automatically after you turn it off. Of course you can also modify this mode manually at any time during this session.

Table of Contents

Training Purposes

Certainly one of the first uses for simulation mode is to learn how to use the unit. Many of the Garmin manuals use this mode to demonstrate and introduce the main features of the product. In addition a store clerk may use simulation mode to demonstrate the product although you may find some of them that don't even know how to turn it on. To highlight this use the e-trex unit calls this mode "demo mode." Demo mode mode differs from standard simulation mode in that a fixed speed is set (20 mph) which causes the gps to appear to move. This can be used to follow a route.

Upon entering simulation mode you will find that the gps seems to have a lock on satellites and everything works similarly to the way it works when you actually have a fix. The satellite status page shows that you have a lock on the satellite graphic display and indicates that you are in Simulation mode in the status text field. The rest of the fields in the unit do not show that you are in simulation mode but may have extra commands or other information and may perform differently. For example, the units with object oriented commands add selection capability for speed and track settings so that you can change them on any screen at any time to permit simulating actual movement while using the gps. Menu oriented units set this information on the original simulation mode setup screen so if you wish to change it you need to revisit the setup screen. The e-trex unit has a fixed setting for speed and track which in consistent with its being called a "demo" mode rather than a full "simulation". Some etrex units also have a "gps off" mode which is similar to demo mode except the speed is set to zero.

The emap has a simulation mode as of the 2.70 release of the firmware. Selecting "Use Indoors" from the map page local memory or "GPS OFF" from the main setup menu will include simulation mode by enabling the gps screen. In previous versions this menu entry was disabled.

  1. Start the gps and turn on simulation mode using on of the above methods.
  2. Select the GPS status screen
  3. You can now use the up/down arrow keys to set speed and the left/right arrow keys to set the direction. Observe the direction by watching a small circle at the edge of the large status circle. It starts out at north.
  4. Once the speed and direction are set you can leave the screen with escape and use the unit similar to other Garmin receivers in simulation mode.
  5. You can return to the GPS status screen to make adjusts in speed or direction.
  6. Turn off the unit or select use outdoors to go back to regular navigation.

You can practice navigation as well as familiarizing yourself with other features. The goto command can initiate a simulated goto with one of the waypoints in your unit. You can add speed to actually "travel" to the waypoint. On older multiplex and G-12 family receivers the object oriented interface will permit you to select speed on the position page or either navigation page and enter the speed you wish. You can also enter the direction by selecting and changing the track display. On the III family you can change to the compass/HSI display page and use the up/down arrows to change speed. The effect of cdi can be explored on the HSI or Highway page using the left/right arrow keys.

Waypoint and Route Maintenance

One of the uses of simulation mode is to allow for route and waypoint maintenance. The e-map considers this use important enough to call simulation mode "inside mode" on that model. While you can perform this maintenance on a unit that is trying to track satellites you may get "poor gps coverage" because you are using it indoors or other annoying messages. Setting simulation mode avoids these messages and as a bonus saves about 1/2 on the battery consumption since in this mode all of the power is removed from the receiver circuitry.

Use this mode when you are downloading or uploading data to and from your pc or when you are just reviewing and fixing names in a waypoint list or building new waypoints or routes from map data. This is also a good mode to use when you need to collapse a few duplicate waypoints that appear due to using the backtrack command. Decide which waypoint you want to keep and then use the 'change' command in the local menu for route editing to change to the waypoint you wish to use. You will need to delete the extra waypoints separately.

On the older multiplex units and the G12 family you can change the location directly on the position page just by selecting it and changing the numbers. This has a number of useful uses. For example you can set the numbers you wish, hit the mark key, and enter the newly made waypoint directly into a route. The route number is remembered from entry to entry so you can build up a route from a map very rapidly using the technique. Another use is to set the current location for viewing purposes on the map page. Since Garmin receivers only show the icons for the 9 closest waypoints to your current location this method of changing your current location can be used to view and perform waypoint maintenance on waypoints that are at far distances from your present actual position. Note that this change will not cause problems when you power off the unit. It will forget the simulation position and remember the previous real position.

The G-III family of units will not let you change your current simulation position in this way. If the new location is not too far you can use the simulator to "drive" there by setting a high speed and track direction. Otherwise there is a neat trick to move the current location. Bring up simulation mode and then simulate a re-initialization of the unit. After selecting this from the status page you can change the location using the map to position the cursor. Once accomplished you will find the simulation mode get a lock at the new location amazingly fast! At this point the 9 nearest waypoints will be computed for the new location.

Using your Garmin as a Calculator

Your gps is also quite useful as a navigation calculator. Using simulation mode for this is not required but is recommended to save batteries and when indoors. While it won't add and subtract a gps is certainly capable of doing several other navigation related tasks.

It can be used calculate the great circle distance between two points. Just put the points of interest and then use the waypoint page to display the distance and bearing. Since your current position is the waypoint named ______ (6 underscores) you can also calculate the distance from your current location.

Your gps supports more than 100 datums. Each waypoint is stored internally using WGS-84 but you can translate it easily to match whatever map datum you may need. Just select the map datum of your choice and the gps will compute and display the new coordinates referenced to that datum. Similarly you can translate from one grid system to another. For example lat/lon can be displayed in degrees and decimal parts of a degree but the unit can just as easily translate those numbers and display in degrees, minutes, and seconds. One really useful conversion is from lat/lon to UTM coordinates.

Similarly you can translate distance from english to metric and back again simply by changing displayed units. You can also convert angular measurements the same way. The current defined magnetic declination will be shown on the auto-mag setup screen. This is done with a table that is stored inside the unit.

Navigation in Simulation Mode

Strange as it may sound there is some navigation features on some of the Garmin handhelds that can be used in simulation mode. In particular any of the newer units support a screen that shows the sun and moon positions. This can be used as a crude compass to determine North and can be quite effective under conditions where you can't get a fix or need to conserve batteries. For rough estimates hold the unit in front of you with North straight ahead and then rotate you body until the sun or moon in the display is approximately where it really is in the sky. You are now facing North. For more accuracy lay the unit on the ground and use a straw placed vertically along the edge of the unit to cast a shadow over the face. Align the unit so that the edge of the shadow from the straw splits the sun and hits the dot in the center of the circle. Now the front of the unit is facing North. Note that this is true north.

The Vista and Summit contain a built in compass and altimeter. These are certainly useful for navigation use even without the standard gps features. Note that "demo mode" cannot be used for this since the compass is disabled in this mode but "gps off" will work fine. If you have a topo map available in the unit you can use the altimeter to help determine your location relative to the map features and topo data and then the "New Location" setting on the status sceen can be used to move your apparent position to the location on the map that you have determined. Then the waypoints you have saved and the maps that are loaded can be used to plan your trip or guide you out of an area where there is no gps coverage. Of course, the compass and altimeter are useful with a paper map as well.

Other Purposes

One of my favorite uses for simulation mode is to playback a route I have saved overlayed onto a map on my pc. Activating a route and providing some speed to the gps will cause it to run the route automatically turning at each waypoint and traveling on to the next. Since all functions are enabled in simulation mode you can turn on the NMEA interface and the output of the simulation run will look exactly like you were really traversing the route. This can be used to display your route on a map or to debug a mapping programs gps interface.

A novel use, submitted by a reader, is to use the gps as a timer. If you set a waypoint as a destination and provide some speed you can watch the screen and use the screen predictions as a timer. If you have an audbile alarm feature on your gps it will even alert you when the cake is done.

00/5/17 initial release
01/03/24 added emap data
01/06/16 added new emap data and more etrex stuff
01/09/22 added description of finding north using the sun/moon display

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