Google Earth

The first thing to know is that you do not have to purchase the premium edition of Google Earth to be able to use it with your GPS, so save yourself the US$20 (unless you also want the polygon drawing tools of course). The way to do it is download your track files to your PC using your GPS PC software, then use GPSBabel to convert the data into a KML file ready to be opened in Google Earth.

Here is a sample of what you will see when you overlay a GPS track and waypoints into Google Earth. This is the Manly Dam Mountain Bike track in Sydney. Using the controls in Google Earth (as shown down the bottom of the image) you can zoom, pan, and rotate etc. You can download sample Google Earth GPS tracks from my MTB Website at http://fatboysbicycleclub.wikispaces.com in the Our Favourite Rides section
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DG Terrain Viewer

You can download the software from the DG Terrain Viewer website. At the site you will see references to the different types of terrain formats that are available. If you are not in the USA (and there's 5.7 billion of us), then the best you can do is 90 metre resolution in the form of SRTM3 data. The data is available from the links on the website. Be aware that the link to SRTM3 World tiles actually links to an old version of the SRTM data at the Nasa website. You can access the newer data by moving up a folder level on the FTP server or by clicking the correct link here. Here is the relevant Australian data.
Now a tip for young players - the tiles are 1 degree lat/long square and are labeled with the bottom left hand coordinates of the tile. So if you are looking for the Sydney region, you would need tile S34E151.hgt (it is stored on the server in a ZIP file).

What you can expect is to be able to create an image like this one. This is Manly Dam in Sydney Australia and the track in the image is the Mountain Bike track that circles the dam.

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Earth Tracker (ie Google Earth Tracker)

You can download the software from the Earth Tracker website. This software lets you take your laptop preloaded with Google Earth in your car, plug in your GPS and watch your self move around in real time in Google Earth - now that's cool. The free version is designed to stop working at random - you get to see how it works, then I guess you pay for it if you like it (the website says it is a nominal registration fee. The instructions say you need to refresh the Google Earth maps on your laptop, then unplug the laptop without shutting down and get in your car and go. In my experience this isn't necessary - I assume Google Earth has been updated so it caches the image files and will operate at anytime off line.
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Geocaching

Geocaching is a game (sport?) where you are given the coordinates for a cache (pronounced cash) which is normally a little treasure chest of nicnaks. The idea is you set off to find it, and once you have found it, you log your visit in a log book and on a web site, take a trinket and leave another trinket for the next treasure hunter. Given that GPS devices are normally only accurate to about 5-9 metres, the cache can still be quite difficult to find, particularly if the person who hid the cache is sneaky.

Now you really can't [easily] use a car navigation system to go Geocaching. The main reason is that in car navigation systems assume that you are on a road, and hence they tend to compensate for slight errors by placing you on a road even if you are not on a road. If your car nav is portable like the Navman iCN 510, and if the Geocache is far enough away from the road then you should be right. Otherwise, read up on why you need 2 GPS devices.

There are 2 great resources to facilitate this game geocaching.com and geocaching.com.au. If you are in Australia, don't dismiss the geocaching.com site. This game is truely international and there are a lot more Australian caches stored on the international site than on the Australian site.

Geocaching is a lot of fun, particularly if you have kids. My suggestions to get you going are:

Go to the geocaching.com web site and register as a user. You don't need to be a premium member and hence it costs nothing to sign up. Give youself a username that is a bit of fun and that you are happy to live with, as once you get going you will start to log your visits to various caches - changing your username later is going to be painful.
In the top RH corner of the web site is the "search for caches..." box. Click on the Advanced Search option, then enter your postcode (this works fine for Australia however not all postcodes have caches - so try variations around your postcode if you luck out) and click Seek.
You will get a list of caches in your postcode area ready for you to set off.
If I am travelling to an unfamiliar area, I find it easiest to look up a postcode of the area before I leave and enter the postcode into this search page. You can find all the Australian postcodes at postcodes.com.au.
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