How to simulate navigation

Some GPS receivers have a simulator or demonstration mode. This is probably one of the most overlooked (but coolest) features on a GPS receiver. The simulator mode acts as if the receiver is actually acquiring GPS satellite information. You select a speed and a direction, and the GPS receiver pretends you’re moving. Because the receiver isn’t relying on acquiring satellite data, you can comfortably sit inside the house in your favorite chair, getting familiar with your new purchase.
Depending on where you live or work, how many windows you have, and your view of the sky, your GPS receiver might (might) work indoors (or at least close to windows). Although you’re limited to what you can do with a GPS receiver indoors, it’s fun to see just how much GPS coverage you can get walking around inside a building.
There are lots more things you can do with a GPS receiver besides using it for basic navigation. Think outside the box. Some examples include

• Take digital pictures of cool places and record their coordinates with your GPS receiver. You can post them on a Web site or e-mail them to friends.
• If you have a small GPS receiver (like a Garmin Geko), securely attach it to your dog’s collar and track where Fido goes for the day. (You can also find commercial GPS pet locator products on the market.)
• Use your track log to create art. Some GPS users express themselves as artists by using their GPS receiver to record their movements as they walk around trying to create shapes or pictures. (Don’t believe me? Check out www.gpsdrawing.com.)

Your goal should be to become confident using your GPS receiver and to have fun in the process.

Finding your ancestors

A lot of people are into genealogy these days, and your GPS receiver can be a helpful tool in tracking your ancestors, whether they are Aztec people or Visigoths. When you visit a cemetery looking for long-lost kin, bring your GPS receiver with you to record the exact locations of tombstones and grave plots. You can pass the latitude and longitude on to other relatives doing their own genealogical research. The coordinates can be extremely useful for someone locating a small out-of-the-way cemetery in the countryside, or a relative buried in a cemetery with thousands of plots.

How far, how fast?

Your GPS receiver also contains a very accurate trip computer that displays information about distance, speed, and time. After you read your user manual on how to reset and start the trip computer, here are some ideas for getting familiar with how it works:

• When exercising: When you run, jog, bike, or whatever, take your GPS receiver with you on your favorite course to see just how far you go. At the end, check your average and maximum speed.
• When on walks: If you have children and they walk to school, go with them on their route to see exactly how far it is. (And then tell them you used to have to walk at least ten times that distance . . . in the snow . . . uphill both ways . . . when you were young.)
• When doing lawn work: The next time you cut the grass, take your GPS receiver with you and see just how far you push your lawn mower. Don't drop and chew the receiver with the mower, if that happen then all my condolence is for you.
  

Coming home

Everyone has opinions and like to know where people stand on different things, so here’s an exercise to let you know exactly where you stand —when you’re outside your backdoor.

1. Take your GPS receiver outside where you live and create a waypoint for the spot where you’re standing.
2. Name the waypoint HOME.
3. Turn the GPS receiver off and go for a walk. How far is up to you, but at least travel far enough that you can see your starting point.
4. When you’re ready to head back home, turn the GPS receiver back on and use it to navigate back to the HOME waypoint.

Be sure to move through the different onscreen pages to watch the direction and distance change as you head back home. After you enter the HOME waypoint, no matter where you are, if you have your GPS receiver with you, you can always tell exactly how far away home is. Remember, this is in a straight line as the crow flies unless you’ve got a GPS receiver that supports autorouting.

How to Use Your GPS Receiver?

Finally! After you initialize your GPS receiver and change some of the system settings, it’s time to use it. Start with _ Going through the GPS receiver’s different onscreen pages and see what information is displayed.

• Walking around and watching what happens to the numbers and your position on the GPS receiver’s mapping and trip pages. (Do this outside, of course.)
• Pressing buttons and seeing what happens. You may want to have your user manual nearby in case you get lost between information screens.

GPS receivers are pretty robust, and you’re not going to hurt your new purchase by being curious.
GPS receiver screens can be scratched relatively easily. Investing in a carrying case will keep the screen scratch-free; many cases have a clear plastic face that allows you to use and view the GPS without taking it out of the case. Another way to keep the screen from being scratched is to buy thin, clear plastic sheets used to protect PDA screens, cut them to shape, and place the sheet on top of the GPS receiver screen.
The following are some simple exercises you can try that will help you become familiar with your GPS receiver. When you first start using your GPS receiver, take the user manual with you. If you forget how to do something or have a question, the manual will be right there for reference.

How to Change GPS Receiver Settings?

After you initialize your GPS receiver for the first time, you need to change a few of the receiver’s default system settings. You only need to do this once, and a few GPS receivers will prompt you to make some of these changes as part of the initialization process. These changes are mostly to customize settings based on your location and needs. Check your user manual for specific information on how to change the system settings described below. Although GPS receivers have a number of system settings that you can change, here are some of the important settings you’ll want to initially adjust:

• Time: Your GPS receiver gets very precise time data from atomic clocks aboard the satellites, but it’s up to you how the time will be displayed. You need to specify
• Whether to use 24-hour (military time) or 12-hour (AM and PM) time
• Whether Daylight Savings Time is automatically turned on and off
• What your time zone is (or your offset from UTC)
• Your GPS receiver gets time data from the satellites in the UTC format. UTC stands for Coordinated Universal Time (no, the acronym doesn’t match the meaning), an international time standard. UTC is a time scale kept by laboratories around the world, using highly precise atomic clocks. The International Bureau of Weights and Measures uses time data collected from the labs to establish UTC, which is accurate to approximately one nanosecond (about a billionth of a second) per day. In 1986, UTC replaced Greenwich Mean Time (GMT) as the world time standard. The Greenwich meridian (prime meridian, or zero degrees longitude) is the starting point of every time zone in the world. GMT is the mean time that the earth takes to rotate from noon to the following noon. These observations have been kept since 1884 at the Royal Observatory in Greenwich, England. In hours, minutes, and seconds, UTC and GMT always have the same values.
• Units of measure: Your GPS receiver can display distance information in statute (such as feet and miles), nautical (knots), or metric (meters and kilometers) formats. The default setting for GPS units sold in the United States is statute, so unless you’re boating or want to use the more logical metric system, leave the setting as-is.
• Coordinate system: By default, your GPS receiver displays positions in latitude and longitude. If you want to use location coordinates in a different format, now’s the time to change the setting.
• Datum: The default datum for all GPS receivers is WGS 84. Unless you’re planning on using your receiver with maps that have a different datum, leave the default setting.
• Battery type: The default battery setting on most GPS receivers is alkaline. If you’re using another type of battery, select the correct type. The battery type setting doesn’t affect the GPS receiver’s operation; it only ensures that the battery life is correctly displayed on the screen because different types of batteries have different power characteristics.
• Language: Most GPS receivers are multilingual, so if you’d rather view the user interface in a language other than English, it’s as simple as selecting a different language from a menu.

The trimble software

During certain times of the day, you might have better satellite coverage than at other times because of the number of satellites that are in view and the position of a single satellite relative to the GPS receiver and other satellites in the constellation.
Trimble Navigation (www.trimble.com), one of the largest manufacturers of commercial and professional GPS receivers, has a free Windows program called Planning, shown in the figure here. Planning is designed for surveyors who need to know when the best time is to use GPS surveying instruments. Just enter the latitude and longitude coordinates of a location and the date, and Planning gives you information on

• DOP: Dilution of Precision describes how accurate a reported GPS position is. The smaller the DOP number, the higher the accuracy.
• Satellites: You can see how many satellites are in view if the sky is unobstructed, the optimumtimes of satellite visibility, and the satellite orbit paths. You don’t need to be a surveyor to use this information. Knowing optimal GPS times is useful for all sorts of outdoor activities. For example, if you’re serious about geocaching, you can select the best time of day to look for caches when your GPS receiver gives you the most accuracy. Planning is easy to use and works for any location in the world with all the GPS satellite information presented in graphs or lists.

To download Planning, go to www.trimble.com/planningsoftware_ts.asp?Nav= Collection-8425.

Preparation for GPS receiver initialization

You really don’t need to know this technical information to operate your GPS receiver, but to start acquiring satellites to get an accurate location fix, a GPS receiver needs the following satellite data:

• A current almanac (rough positions of all the satellites in orbit)
• The GPS receiver’s current location
• The current date and time
• Ephemeris data (precise position of individual satellites)

If some or all the data is missing or out-of-date, the GPS receiver needs to get updated information from the satellites before it can accurately fix a current position. The types of data that are outof-date or missing determine how long the GPS receiver takes to initialize. If the GPS receiver is brand new, out of the box, several hundred miles away from where it was last used, or has been stored for a prolonged period of time, initialization will take longer.

How to Initialize Your GPS Receiver?

Your GPS now has power, so it’s ready to go, right? Well, almost. After you put batteries in your GPS receiver and turn it on for the first time, don’t expect it to instantly display your location. A GPS receiver first needs to go through an initialization process before it can tell you where you are. The type of initialization and the amount of time it takes depends on what information the GPS receiver has previously received from the satellites and when. The process is mostly all automatic, and you don’t need to do much as your GPS receiver starts up and begins to acquire satellites. Your GPS user manual may contain model-specific initialization information. To initialize a new GPS receiver, take it outside to someplace that has an unobstructed view of the sky (such as a large field or a park) and turn on the power. (You did install the batteries first, right?). After the start-up screen displays, the receiver will begin trying to acquire satellites.
It can take anywhere from 5–30 minutes for the GPS receiver to gather enough satellite data to get a position fix for the first time (usually more toward the 5 minutes end of the scale). Don’t worry; your GPS receiver isn’t going to be this slow all the time. After the GPS receiver is first initialized, it usually only takes 15–45 seconds to lock on to the satellites when you turn it on in the future. In order to speed up the location fix for the first time or when the GPS receiver has been moved hundreds of miles since it was last turned on, many GPS receivers have an option where you move a cursor on an onscreen map of the United States or world to show your general location. Providing a general location helps the GPS receiver narrow its search for satellites that are visible from your present location, speeding up the initialization process. Manufacturers often use the terms cold start and warm start to describe different GPS receiver start-up states and times. Unfortunately, their definitions of these terms can be different, which makes comparative information about start times not very useful. Just remember that under the same conditions, with a similar view of the sky and with their antennas optimally orientated, most modern GPS receivers generally take the same amount of time to acquire satellites and fix a location.
Most GPS receivers have a satellite status page that’s displayed while the receiver is acquiring satellites; see an example status page in Figure 5-1. This page typically consists of two circles that represent a dome of sky above your head. The outer circle is the horizon, the inner circle is 45 degrees above the horizon, and the center of the inner circle is directly overhead. The N on the page represents north.
Based on the almanac information, the GPS receiver shows the position of satellites within the circles, representing them with numbers. As a signal from a satellite is acquired, the number is highlighted or bolded. Underneath the circles are a series of bar graphs with numbers underneath them that represent signal strength. The numbers correspond to the satellites that the GPS receiver has located. The more a bar is filled in, the better the GPS receiver is receiving signals from that particular satellite. Try moving your GPS receiver to watch the satellite signal strength change. If signals are weak or you get a message about poor satellite coverage, move to another location and change the position of the receiver to better align it with the satellites that are shown onscreen. If you’re successful, you’ll see new satellites acquired, the signal strength increase, or both. The more satellites you acquire and the stronger the signals, the more accurate your receiver is. Holding the GPS receiver properly will optimize signal reception. If your GPS receiver has a patch antenna, hold it face up, parallel to the ground. If your GPS receiver has a quad helix antenna, hold it straight up so that the top of the receiver is pointing toward the sky.
After the GPS receiver gets enough information from the satellites to fix your location, the screen typically displays an Estimated Position Error (EPE) number. Based on the satellite data received, this is the estimated error for the current position. The smaller the number displayed, which will be in feet or meters, the more accurate your position.
Estimated Position Error (EPE) is a bit confusing. If you see an EPE of 20 feet, it doesn’t mean that you’re within 20 feet of the actual coordinates. You’re actually within up to two times the distance of the EPE (or even more) from the actual location. For example, if you have an EPE of 50, your location could be 1–100 feet of the actual coordinates. EPE is not a maximum distance away from the actual location; it’s only a measurement estimate based on available satellite data. To complicate things even further, different GPS receiver manufacturers use different formulas for determining EPE, so if you set three different GPS receiver brands next to each other, they all display different EPE numbers. Some manufacturers are conservative with their numbers, and others are optimistic. Don’t get too caught up with EPE numbers; just treat them as ballpark estimates — and remember, the smaller the number, the better.

More about GPS battery

After you select the type of batteries you’re going to use, you should be aware of some other issues when it comes to powering GPS receivers:

• Battery life gauges: In the GPS receiver’s setup information page, you can specify what type of battery you’re using, such as alkaline or NiMH. The battery type setting helps the GPS receiver make an accurate guess how long the battery will last. Remember that different battery types have different discharge rates. All GPS receivers also have an onscreen battery gauge that shows you how fully charged the batteries are. If you set the wrong type, the worst that will happen is that the gauge won’t be accurate. See how to extend battery life with some GPS receiver models in the sidebar, “Battery saver mode.” Always check the battery level of your GPS receiver before you head out on a trip and also remember to carry spare batteries. One way to tell which batteries are new or charged is to put a rubber band around the good ones. By feeling around in your pack or pocket, you can instantly tell which ones are fresh. Note: Rechargeable batteries discharge faster than alkaline batteries when they’re not in use, so if you haven’t used your GPS unit in a couple of months, don’t be surprised if those rechargeable batteries are dead or don’t have much life left in them.
• Cigarette lighter adapters: If you’re primarily using your GPS receiver in a car or truck, you can save on battery costs by powering the GPS receiver with a cigarette lighter adapter. These handy devices run a GPS receiver from your car’s electrical system. You can buy a generic version or one made for your model (sold by that GPS receiver manufacturer). Depending on the model, adapters cost between $20–$40, with the generic versions a bit cheaper than the manufacturer models. Cigarette lighter power adapters have straight or coiled cables. Although coiled cables are tidier, if your cigarette lighter isn’t close to the dashboard, a coiled cable can pull your GPS receiver off the dashboard if it’s not securely mounted. Adapters with straight cables don’t have this problem; you can tidy up any slack in the cable with a plastic zip tie.

Battery saver mode

Some GPS receivers have a battery saver mode that can greatly extend the life of your batteries. (Check your user manual to see whether your model has this feature and how to turn it on.) Normally, a GPS receiver processes satellite data every second and determines your speed and location. Based on this information, the GPS receiver predicts where you should be the next time it gets satellite data. If the prediction is close to your actual position and battery saver mode is turned on, the GPS receiver will start receiving satellite signals every five seconds or so instead of every second. In addition, some of the internal electronics are turned off during this wait period. Because a reduced amount of power is needed, the battery life is extended. The GPS receiver continues to access satellite data every five seconds until the predicted location isn’t accurate anymore, at which time it switches back to receiving data every second, starting the process over again. (Some GPS receivers provide you with a number of choices of how often satellite data is received. The more seconds, the more battery efficient the receiver is.)