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Using an application such as RoboGEO (www.robogeo.com) to incorporate GPS positional data into your digital photographs makes recording and documenting points of confluence easier.

Benchmarking/Trigpointing

We now move on to finding not points on the globe, but real things. Benchmarks and trigpoints are points used by mapmakers when surveying. They are known points of the Earth’s surface that have been accurately marked. The benchmark is a physical object — usually a concrete pillar or a metal disc, as shown in Figure 12-4.

FIGURE 12-4: A trigpoint

Trigpoint — short for triangulation point — is the term commonly used in the U.K., but it is included here because it is now used in the U.S., too.

On these pillars or discs will be information that is used for logging. Sometimes it is just an ID for the marker, while other times it may be more. There is nothing inherently exciting about the actual marker or the places where they are located. It simply goes to show that if people are made aware of a given point somewhere, some of those people will want to seek it out.

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It seems that the government departments responsible for keeping track of these markers (the United States Geological Survey in the U.S. and the Ordinance Survey in the U.K.) approve of benchmarking because benchmarkers visiting them can report on any damage that they have suffered, or that they are missing.

Finding benchmarks isn’t hard. Some are marked on maps. However, the digital age has made finding them much easier, and now the main geocaching website (www.geocaching.com) lists benchmarks in the U.S.

For a listing of U.K. trigpoints, visit www.trigpointinguk.com.

Finding benchmarks is a matter of logging on to www.geocaching.com and doing a search. Start off by doing a search of your local area (you can search based on zip code). This should (hopefully) pull up a big list of them. For your first outing, it is advisable to pick a benchmark that has already been visited by others — this enables you to confirm that it is actually there (or was on the date of the last find). More important, the log might contain a photograph that you can use in your hunt.

After downloading the coordinates to your GPS, simply follow the pointer until you get close. However, now things get interesting. You are looking for something that is not hidden per se, but it might not be too obvious. Finding huge concrete pillars is easy, but finding a small nondescript bolt in the ground can be quite hard, so you may need to search for a while before you find it. Console yourself, however, with the knowledge that the more you find, the easier it becomes!

Once you have found the benchmark, you can log it. There are no logbooks to fill in or swaps for you to trade, but you can take the details off the marker. You can also take a picture of it (put your GPS in the shot if possible).

When you get back to your PC, you can log your find on the geocaching website.

Don’t go out benchmarking expecting a find every time. Many benchmarks are old and damaged, missing, or in overgrown areas.

GPS Drawing

Many GPS units are now capable of displaying a map. This can either be a detailed map, showing roads, rivers, coastlines, and contours or it can be a very simple map showing nothing more than waypoints that you have entered. What both have in common is that they will be capable of displaying the trail you have navigated on the screen with the map. This trail, known as a track or breadcrumb trail, is the log of the path that you (or, more accurately, the GPS) took. When these units became more popular, they spawned a new GPS-related hobby — GPS drawing!

GPS drawing (sometimes called geo art) is an activity in which you walk around with a GPS switched on and track your position, and then you use the track or breadcrumb trail to create a picture on the screen of the GPS. Figure 12-5 shows an example.

Seems easy — but it isn’t. You have to make really huge movements in order for them to appear on the screen, which means that you need a lot of space in which to work. It’s also good to have a plan in advance.

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FIGURE 12-5: A GPS drawing

Of course, there is a website that is devoted to GPS drawing — called, unsurprisingly, www.gpsdrawing.com.

You can carry out GPS drawing in any activity that you do outdoors — walking, hiking, jogging. But why be restricted? What about having a go while skiing? Or cycling? In the car? You don’t even have to be limited to being on the ground! Even pilots, sailors, and skydivers can enjoy GPS drawing!

Here are some tips for newcomers to GPS drawing:

You need plenty of space to do even the simplest GPS drawing. Flat ground without hedges, walls, streams, and rivers is ideal.

Steer clear of cliff edges, mountainsides, and other dangerous areas.

You will need a mapping GPS unit — it’s nearly impossible to use any other kind of unit (unless it is hooked up to an external device, such as a PDA).

For the best drawings, you need a clear view of the sky. That rules out wooded areas and deep valleys or ravines.

Make sure you start off with new (or freshly charged) batteries. Some GPS units will lose the breadcrumb trail if they shut down because of flat batteries.

It might be a good idea to practice before trying something ambitious. Try following the markings on a football field or parking lot.

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Make faint lines by doing one pass. To make lines that are thicker or bolder, do multiple passes along the same route. The more passes you make, the darker and thicker the lines will appear. You can also use lines consisting of various numbers of passes as shading.

The slower you go, the thicker and darker the line will appear. Therefore, the thicker lines will represent areas you’ve traversed several times slowly, and the faintest ones will represent areas you’ve covered only once, and fast.

You might find it handy to use small markers as you draw. Depending on the area you are in, you could use stones, sticks, or golf tees. The easiest terrain to GPS draw in is sand.

Don’t worry if you make minor mistakes — these are common. Just pick up from where you went wrong and continue.

After you are done, save the log of your track to prevent it from being deleted or overwritten (consult your GPS manual for information on how to do this).

Finally, if you have mapping software, import the log of the track into that for a better view.

For more information on GPS drawing visit www.gpsdrawing.com.

Hide-and-Seek

Why search solely for inanimate objects with your GPS? Geocaches and benchmarks are very well and good, but you can put a new twist on hide-and-seek with your GPS.

For this game, you need a GPS and a walkie-talkie. The walkie-talkie enables you to transmit your coordinates to the other players.

To play this game properly, you really need more than two people, preferably two teams. One team does the hiding while the other team does the seeking. You can add all sorts of variations to this game (such as playing it at night as a stalking game in which the seeking team has to sneak up undetected on the hiding team).

You can also employ some aids in this kind of game to help it along. One such aid is the Garmin Rino GPS receiver. This is a combination GPS receiver and walkie-talkie that enables you to transmit coordinates from one unit to the other (as well as transmitting voice). This is known as an Automatic Position Reporting System (APRS).

Garmin Rino GPS/walkie-talkie hybrids are also excellent for families that want to keep in touch while on the move outdoors.

You don’t need Garmin Rino GPS receivers to do this, however. If you have a GPS such as a Garmin eTrex (in fact, all modern Garmin units as well as Magellan units will do) and two FRS (Family Radio Service) two-way radios (these need to have headphone and microphone connectors on them in order to interface), you can do the same thing — well, you do need two other kits: One is called a TinyTrak3 and the other is a Terminal Network Controller (TNC). You will also need to make a few cables.

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To summarize, you will need the following:

2 GPS receivers

2 FRS two-way radios

Set of cables for connecting the units together (covered shortly)

1 TinyTrak3 kit

1 TNC kit

1 PDA (for viewing locations). The only ones I tested are Palm devices running 3.01 they must have a serial port. Alternatively, a laptop will do.

The TinyTrak3 is a GPS position encoder and is available from www.byonics.com/tiny trak in various forms (kit or ready-made). Prices start from $36 for TinyTrak3 in kit form.

After you have assembled the TinyTrak3 (it requires soldering but nothing difficult is involved), you can program it by connecting it to a PC via a serial port and running the configuration software, shown in Figure 12-6.

FIGURE 12-6: TinyTrak configuration software

Some important features of the configuration interface include the following:

Callsign: If you are using the system with an amateur radio kit, this is where you would put your FCC callsign. If you are only using FRS two-way radios, you can put any sixcharacter ID here.

Digi Path: The default value of WIDE2-2 is correct for this.

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Auto TX Delay: This sets the delay (measured in milliseconds) between pressing the transmit key and sending the GPS data. Set this to 300.

Auto Transmit Rate: This sets the interval between GPS updates. This can be whatever you want, but you should set it to a short interval initially so you know that the system is working. I recommend between 5 and 120 initially.

Quiet Time: This sets the duration during which the radio channel must be quiet before the system transmits a location packet. If the channel is shared with voice, set this to 500.

MIC-E Settings: Leave these options disabled.

Once the preceding settings are specified, the TinyTrak3 is ready for use.

Next, you will need to assemble the TNC. This is available in kit form from http://john. hansen.net (this is much cheaper than buying a readymade kit, which can be expensive). Currently, the kit retails at $45. Assembly of this kit is straightforward, but like the TinyTrak3, it requires some soldering.

Then you need to assemble the cables, of which there are three. Before you begin assembly, you need a conductor plug that fits the headphone and microphone socket for your radios. These are available from electrical outlets or you can cannibalize an old set of headphones and microphones for the job.

The first cable is a GPS-to-serial port cable, the assembly of which is described in Chapter 2.

Next is a cable to connect the TinyTrak3 to the radios. Figure 12-7 shows the wiring details for the cable to connect the radio to the TinyTrak3.

5 9 4 8 3 7 2 6 1

+5V

GND

5 9 4 8 3 7 2 6 1

To TinyTrak

FIGURE 12-7: TinyTrak wiring diagram