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GPS and Cub Scouts

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I've been asked to do a presentation for our Cub Scout pack on geocaching and how GPSr's work.


I can boil down an explanation of geocaching for the younger minds ( 6 - 11 year olds), but does anyone have an age appropriate description of how to describe how a GPS system works?


I know how to describe it to an adult (both a general purpose adult and a mathematically / engineering inclined one) but how do you distill it for the younger audience?


Any thoughts would be appreciated.

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There’s no point delving into any math at that age. Atomic clocks, nanosecond timing, and complex math are way beyond what they would comprehend. A quick demonstration will give them plenty to ponder.


To illustrate the satellites, put 3 scouts at various distances from the center of the room. They are the "satelites". Do a countdown and have all of them roll a marble (the signal) at the same speed toward a target (GPS receiver) in the center of the room (may need to build some short ramps to release the marbles at the same speed). They’ll see that the “signals” arrive at different times at the "gps receiver"


Then draw one big circle explaining that the center is the satellite and the size of the circle shows the time it took for the marble to roll. Ask them to show you where they are on the circle. After you let them discuss it for a while, draw a second circle of a different size and show them the two points of intersection. After you show them that they could be at either point, ask them to figure out how to resolve it. You’ll get some interesting ideas! If they don’t come up with the answer put in the third circle and talk about why a minimum of 3 signals is necessary.


That should be enough explanation for that age, but be prepared for some off the wall questions.


[This message was edited by Moore9KSUcats on March 12, 2003 at 11:30 AM.]

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Teach them what triangulation is by selecting two volunteers. Have them stand five or six feet apart. Give the first boy the end of a string which is four or five feet long (distance A). Give the second boy the end of a longer piece of string (distance :o.


Explain that there is an object positioned at distance A from the first boy and at distance B from the second. Ask, "where is that spot?" -- it's at one of two points where the circumferences swept out by the string/radii intersect.


Next, grab the two free ends of the strings and pull them taut. Explain that the two volunteers are like GPS satellites and that if you had a GPSr it would receive signals from satellites which tell the unit how far away they are (i.e. "how long the string is"). If they ask how that's done, you could draw an over-simplified analogy to counting the elapsed time between a lightning flash and a thunderclap to figure out it's distance.


Explain that the satellites use very accurate atomic clocks, and that you actually need at least 3 sats for a 2D global position and 4 sats for 3D (position plus altitude).


Then if you think they can handle the jump, show them the following website (or just print a picture of a calculated position):




Hope this helps,



[This message was edited by Cache'N'Carry on March 12, 2003 at 11:44 AM.]

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Hey Poppa Duck, I'm a cub scout den leader and just got back from teaching the boys how to carve ivory soap with a plastic knife. Was wondering if you would be willing to post here how it went (teaching the boys about GPS's and Geocaching.) I'd be interested to see. Thanks! icon_smile.gif

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I just did a breif overview of GPS last night for our den. The way I presented it to them was that there were a bunch of sat.'s that sent down a radio signal and allowed you to know where you were.


By Far they were much more interested in the Geocaching part of my discussion. I'd keep it breif as any technical information is quickly disregarded in lieu of idle kid chatter. icon_smile.gif








Cache'n Retrievers


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Thanks to all for the suggestions. I like the two using the volunteers. I'll take them to heart as I plan the lesson.


The only problem with the existing websites out there( re: how stuff works), is that it's good for an adult, but I think it's still too complicated for the kids.


I'll let you all know what I come up with and how it works out.

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When I had to teach it to my son's scout troop I use the FAQ page from here and kept it simple on the gps stuff and concentrated on the planning and going on the hike for the cache.


We have been on 3 now and the youth love them.


I might still have the lesson I will let you know.






Ontario geocachers http://groups.msn.com/GeocachinginOntario/homepage

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I did a demo for scouts that age, I used the desciption from HOWSTUFFWORKS web sit and i hide three caches ahead of time out in the playground and put ring pops in each, then broke them into three teams and sent them on a search. all three were found without a problem and several now geocache with their dads.

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With great ideas. I'm looking forward to using some of these ideas in a future pack meeting!


Thanks everyone for sharing the info (especially the how-stuff-works website - that's going to be an often referenced site as my kids grow!)


- HartClimbs


"If someone did you a favor - something big, something you couldn't do on your own, and instead of paying it back, you paid it forward to three people...and the next day they each paid it forward to three more...and the day after that, those 27 people each paid it forward to another three...and each day, everyone in turn paid it forward to three more people...in two weeks, that comes to 4,782,969 people."

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Hi Poppa Duck

I'm a Cub Leader in the UK too and since discovering Geocaching in January I'm totally hooked and trying too to find a way to involve it in Cub meetings. As GPS's aren't that common in the UK yet I don't think a talk to my cubs about GPS would be much use - but they are up for finding treasure and the travel bugs are great for teaching geography. If you think of anything, maybe our Cubs could get in touch with your Cubs. We have about 15 boys and they're mostly either 8 or 10 (not many 9 year olds). We're based in the South of England, midway between London and the coast and the setting is pretty rural (we have to cross a stream on a wooden bridge to get to the hut).


I was thinking of getting the boys to help plant a cache locally (but maybe not tell them exactly where it is!).

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Thanks again for all the suggestions.


We actually decided to break this out over several pack nights. The first one was the other night. I introduced the topic as "who wants to go on a treasure hunt" and it worked pretty well.


All I covered was geocaching in general and used several boys to give a demo of the concept of how the GPS works - about 15 to 20 minutes total. I put together a super size demo cache using a big pretzel jar that everyone got to hold and look into. I also had a single page handout that everyone took. It was an abbreviated version of the FAQ on one side and several pictures / diagrams of the GPS satellite network and how the concept works.


Funny thing happened that both the Cub Master and I picked up on. I figured I'd loose the younger kids attention span and keep the older ones interested. Exactly the opposite happened - the Weblos wandered off during the demo, but the Tigers, Bears and Wolves stayed with it.


The next phase will be at our May meeting. Traditionally it is the spring carnival - we're going to add a geocaching segment on the school grounds. I figure for the younger kids make it a treasure map based experience and for the older ones let them use the GPS to find several caches.


I'm also hiding a real cache in one of the campgrounds that we use that already has several cache's. On our next overnight the boys can search for it and see who/what has been traded.


All in all, I think it's working out quite well and hopefully several of the boys and their parents will get hooked.

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Just to close out this thread, the scouts finished off their geocache experience last night.


I hid three caches on the school property and for the younger kids gave them a treasure map and the older kids just the coordinates and a gps.


Everyone had a great time and went home with plenty of booty.


If anyone is interested in the materials I put together, just let me know.


-Poppa Duck

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Some good ideas here. I know that some closeby Scouting groups have done a wee bit of GeoCaching and I'm very much interested in getting some Cubs/Scouts out next Season. Might even get them looking for one that I hide!

A great way to "Keep the 'OUT' in ScOUTing!"


"Dr. DumbAss, he da man!

If he can find it... anyone can!"

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