Saturday, February 23, 2008

Go away, anchors! Bad anchors!

I'm planning a puzzle cache called Anchors Aweigh! So I checked to see how many geocaches have this name. The answer is 13. For fun, I checked to see how many geocaches have the name Anchors Away! The answer is 20. I decline to draw conclusions about geocachers from this. I will say that none of the Anchors Away! caches are in Minnesota. We're a smart bunch.

By the way, the cache is about ANCHORS in the context of a mathematical algorithm. Can you guess what it's about?

An embarrassment of riches in the way of geocaching social events lately: WeekNight caching in Ham Lake on Wednesday night, and Breakfast Buddies in Richfield this morning.

The highlight of the Ham Lake outing was the spectacular lunar eclipse overhead. It was also nice to hang out with topgear, Bus&Betty, and sir_zman. I hadn't met topgear before, but I had found some of his caches, so it was cool meeting him by accident at his own awesome puzzle cache ORIGAMI FLYING BIRD before the WeekNight. We all ended up at the Green Mill for dinner, but getting there was a trick. sir_zman gave me coordinates for the restaurant, but they took us both to an industrial park across the street from the complex that Green Mill is in. zman put his geo-sense to work, but I had to stop in at a Walgreens for directions before logging the dinner smiley.

Also, along the way to dinner I stopped off for a quick one, The Puck Stops Here!, another topgear cache as it turns out.

Two FTFs in the last couple days -- a poppa99 footbridge cache in Bordertown (nice meeting him at BB today), and a Bobcam puzzle cache, his first out of 85 hides. The Bobcam cache I DNFed last night with mini-bass, but I had solved the puzzle correctly. Bobcam had a little kink to work out of the puzzle (I've been there, I understand!), so I went out there again with Millah with the correct coordinates, and we still couldn't find it. A quick phone call to Bobcam produced the hint we needed, and one ripped Millah down coat later, we had our co-FTF. On to Richfield.

The Old Country Buffet was crawling with geocachers! I think the management was a little nervous, but they got our money, so it's all good. Who did I meet or talk to? I know I'll forget someone, but I'll give it a shot:

  • Millah
  • Pippin and Merry
  • Bus&Betty
  • topgear
  • Bobcam
  • knowschad
  • sir_zman
  • two of hearts
  • Oneied Cooky
  • TheCollector
  • minnesotabrad
  • Moe the Sleaze
  • poppa99
  • speedysk1
  • RubberToes
  • Red_Devil35
  • Jonas
  • GeoPierce

All these people to give pathtags to, and wouldn't you know it, I got a call from my wife a half-hour after the event to say that my pathtags had arrived in the mail. (Isn't it sweet that she recognized the importance of this fact?)

Congratulations to Millah on his 500th cache find -- Picture Sudoku -- which we picked up after the Breakfast Buddies event along with several others as we bumped into multiple cachers on the Traveling After Party Event Cache. We celebrated Millah's milestone with a Flat Earth Cygnus X-1 beer afterwards (we did not play Hemispheres [edit: Cygnus X-1 is on Farewell to Kings] by Rush, however). Millah gets Pathtag #1. Now, it's time to address some envelopes. Fifty pathtag trades to make good on. I turned off the trade button, but I'll be happy to trade with local cachers!

Monday, February 18, 2008

V = (4/3)*pi*r^3

Thanks to sir_zman, host of the Twin Cities Geocaching Podcast, for his kind words about this blog in his 2/18/08 podcast. Since he mentioned the math content of this blog, here's a related rates problem for you: if the radius of my head is growing at a constant rate of 50 meters per second, then at what rate is the volume of my head growing when its volume is 100 cubic meters?

If my head grows to 100 m^3, then you, the reader, won't have to worry about the wild success of this blog leading to advertising content; I'll just sell ad space on my forehead. Hm, that'll make stealth difficult on those urban caches... I should rethink this.

Seriously, I don't think I have anything special to offer here. I am no fountain of knowledge about geocaching. In fact, almost every geocacher I know has more cache finds than me. But if someone sees something here that leads to another social connection -- of which I've enjoyed many already -- then it will have served its purpose. It's a sort of virtual event cache.

Thanks also to zman for choosing not to broadcast the story I told at WeekNIGHT in Cottage Grove about my disturbing the natural environment of Lakeville in reckless pursuit of a cache. I guess he didn't want it construed as endorsement of a particular brand of chainsaw. Kidding, kidding... still, I don't want it to get around.

In other news... rickrich had to remove the Where's Yoda calculator from his webspace; his ISP identified it as malware. I think it's because the puzzle is based on the Pythagorean Theorem. Shady Pythagoreans... has changed the status of my order from "unshipped" to "in progress". Could it be?! Maybe I'll have some tags to share in time for Breakfast Buddies in Richfield on Saturday... two FTFs in two days: knowschad's Little Crow and Millah's A or A ?... 25 caches on Sunday, most of them orange... in case you haven't noticed, Bobcam -- prolific Twin Cities cache hider and finder -- is 4th (down from 2nd; come on, Bobcam!) in the USA in Find Rate, according to INATN. Started at the end of September 2007, has >1000 finds... WeekNIGHT is at Ham Lake on Wednesday. I have new tires, so I might be able to make it.

Saturday, February 16, 2008

gpx2ipod problem solved

One problem is solved on the quest for paperless perfection. I investigated the files that were being corrupted between the .gpx file and the Notes folder of the iPod, and I realized that any cache name containing a colon wasn't being handled properly. It appears to me that the gpx2ipod script was trying to fix the situation by replacing the colon with a slash, which seems like an odd choice, and then when these files went to the ipod, everything in the cache name before the slash was missing, and the body of the note was empty.

Out in the field I only look up caches by GC number, so I edited the script to write only the GC number, not the cache name, as the name of the note.

I replaced

cat - $tmpfile <<<$xmlpretext > "$outpath/$cacheid $name"


cat - $tmpfile <<<$xmlpretext > "$outpath/$cacheid"

Works like a charm. There is still the issue that the iPod doesn't like notes that are bigger than 4k. Not much of a problem, though; in my last pocket query of 500 caches, there were 12 files bigger than 4k.

Friday, February 15, 2008

The quest for the perfect paperless experience

When I first started pulling pocket queries and stopped printing out cache pages, I used gpsbabel on my Mac laptop to load caches on to my Garmin Vista through the serial adapter and a USB-serial converter, and I used gpx2ipod to load caches into the Notes folder of my iPod in disk mode. Around the time I got the Garmin 60CSx, I began to experiment with MacCaching and CacheMate to load caches on to the 60 (USB!) and a Palm III (through its serial adapter and the USB converter) that I bought in 1999.

Two things became obvious very quickly: first, it took the Hotsync manager about TWENTY MINUTES to load a 500 cache .gpx-turned-.prc on to my Palm III (which I think may be made out of wood, I'm not sure). Second, MacCaching is just not happenin'. Its map utility plots the first five caches in the database and that's it. Useless.

So, back to gpsbabel and gpx2ipod. I am trying to address the map issue by investigating some Linux tools like gps-map that rickrich has developed for use with gpsbabel. Still working on it -- I had to install Xcode and MacPorts, and I think something may still be missing, or I've got something in the wrong directory. Work in progress.

gpx2ipod is also fluky. It puts Notes on the iPod at a blazing speed, but sometimes I'll get out to a cache and realize that the relevant cache file is missing. Also, sometimes it chooses the filename to be the GC number and other times the filename is the cache nickname. Maybe these are the same issue.

Until I get in the groove, I am printing screen shots of the Google maps interface and WRITING in the GC numbers near the icons. How lame is that?!

Thursday, February 14, 2008

My first WeekNIGHT

I went to my first WeekNIGHT caching event last night in Cottage Grove. This one was hosted by broken tooth. It was nice socializing with everyone, including:

  • Millah -- I picked Millah up, and we thought we'd have all kinds of time for pre-caching, but we pulled into Hamlet Park's parking lot just in time to start. We underestimated the time to get to Cottage Grove.
  • broken tooth -- A couple weeks ago I grabbed an early morning puzzle cache that was placed by broken tooth's son K-3. I thought I might get FTF on that one, but when I pulled into the parking lot, Millah and DLHCacher were chatting, having just found the cache.
  • sir_zman -- It was nice to meet him finally, after emailing back and forth about ways to use geocaching in educational programs. He spent some of the time (but not ALL of the time!) capturing audio, presumably for his podcast.
  • Bus&Betty -- The nicest couple you'd ever want to meet. There are a lot of nice caching couples in the Twin Cities! They do a lot of traveling and so had stories about how the natural pitfalls of geocaching are different in different places.
  • cstjohn -- We talked a good bit about pathtags and the perils of turning on the "allow trades" button. I grabbed her pathtag out of Due We Dez Maul, the awesome library cache up in White Bear Lake.
  • TheCollector -- Millah and I grabbed his mall series in Burnsville on the way down to Lakeville last Sunday, and we also found an unpublished cache of his without realizing it. He was trying to publish in a place near the final location of a puzzle cache (that we were looking for).
  • MN_Cavepeople -- with the understated and wry sense of humor. I mean, just look at the picture on his profile! It was great telling stories with everyone over dinner and drinks at Ruby Tuesday.

I took a wrong turn on the way from the caching to the restaurant, and Millah and I found ourselves within 100 feet of a nano cache in front of a grocery store, so we stopped and picked that one up on the way to dinner. I think some of the others stopped for that one after dinner.

Getting home was not pleasant. The roads were horrible. In fact, the old '99 Accord is getting new tires today. Also, I had to make an emergency Valentines stop for the kids. Can't leave any of their classmates out on Valentine's Day. When you have twins, you have to get two of everything, and when they're giving Valentines to their classmates, that adds up!

What am I giving my kids for Valentine's Day? How about the gift of me not geocaching? Maybe some other stuff too. That's not totally fair -- the mini-double-bass likes geocaching too!

Where's "Where's Yoda?"?

Blogger has disabled my page Where's Yoda? due to a violation of Terms of Service. I doubt that it's because there is a photo of a Yoda Pez dispenser that I did not take myself. Reading the discussion groups, I think that a bot has identified the script on that page as spam. Many people are finding it difficult to get responses out of Blogger, so I am not optimistic that it will be up and running anytime soon.

Anyone have suggestions on where to host this little calculator? I don't want to put it on my work web space, and I don't want to pay.

When our local cache reviewer asked me to move that calculator off this blog, because Groundspeak doesn't want cache pages linking to commercial sites, he was doing me a favor; otherwise, this blog would now be disabled. Who knows, maybe it will be soon, and I'll have no idea why and no way of finding out.

UPDATE: rickrich has generously offered to host the Where's Yoda? calculator. Blogger can take their sweet ol' time. And they will.

Monday, February 11, 2008

Time to take a deep breath.

After publishing Where's Yoda? last week and amusing myself and, I hope, others with alternate approaches to a solution, I turned my attention on Saturday to closing out the Plato's Five Gems series. I had the kids for the afternoon at Edinborough Park in Edina (and of course checked for nearby park'n'grabs, but the timing didn't work out), so I was free for a little while on Saturday evening to place Dodecahedron and Bunganator's Grand Slam.

I had previously released Octahedron, Icosahedron, Tetrahedron, and Cube, and so I returned to those caches to drop off clues for the Grand Slam. When I returned to my marked location for Dodecahedron, I was alarmed that the coordinates were a good bit off, but I hope that the geobeacon that the cache sits in will announce its presence enough to forgive some fluky coordinates. It's hard to juggle coordinate changes and the fact the puzzles are closely tied to the digits.

The Grand Slam cache was fun to place, because the cache itself is an icosahedral die. A very small number of cachers have the clues from all four of the old caches in the series (I'm emailing them to previous finders on request), so it could be a while until Grand Slam is found.

It was a little nerve-wracking Sunday and Monday, because I placed Dodecahedron too close to an unsubmitted cache that of course I was unaware of. But thanks to some mysterious and much appreciated dealings between our hard-working local cache reviewer and a gracious fellow cache hider, Dodecahedron was allowed to nestle in among its friends.

I must say, for the record, that I believe cache hiders should not be allowed to hold a location by reporting a cache but not submitting it. Priority should be given to the first to submit, not the first to report. That said, it has happened to me twice out of nine hides so far, and it has worked out for the best in both circumstances.

This is particularly bothersome for folks who hide mainly puzzle caches, because often the puzzles have to be reworked if the final location is changed.

Sunday Millah and I headed to Lakeville, mainly to finish off Bunganator's Climb On series of puzzle caches about rock climbing. We tried to pick off some traditionals in the area, too, and toward the end of the trip, we realized that we had around 25 finds and that I might be close to 300. Turns out, I was at 297 at the end of the day, so this morning I grabbed two on the way to Millah's puzzle cache Read 'Em And Weep, which came out of King Boreas' awesome Jukebox Hero seed cache.

Time to take a deep breath. Nine cache hides feels like plenty right now.

Friday, February 8, 2008

The backdoor to Where's Yoda?

One thing I love about geocaching is that each person can interact with the game/sport/hobby however he or she chooses. If you pull out a laptop at a pick-up soccer game, you will get looks.

Yesterday, I published a puzzle cache called Where's Yoda?. In order to solve the puzzle, the cacher uses a Javascript calculator that I hacked together from some code I stole from a colleague. That calculator is now here and not on this blog because does not like it when cache pages re-direct to pages that have links to commercial sites, as I do here (for convenience, not necessarily to promote those products).

I am fascinated with ways that cachers can get around actually solving a puzzle. One way would be to look at the code in the page source for the calculator, so I had to figure out how to encrypt that code. (And if you can decrypt that, then more power to you!)

Another way that cachers get around solving puzzles is by flooding with checks until they hit Success! This Yoda puzzle has 10^6 possible answers, so that's not really a problem here.

A third way is by plotting possible answers on Google Earth. For example, on Millah's musical puzzle cache Final Countdown I didn't have the hundredths of west or the thousandths of north, so I plotted a rectangle in Google Earth and guessed where it should be (incorrectly, it turns out).

In order to discourage this, once the cacher finds the coordinates of Yoda (X,Y), I give the cache coordinates as (7X-2Y+230,Y^2-7X^2-48339), so that distances in Yoda-land don't correspond to distances in cache-land. (I realize that a box of 1'N by 1'W is not a square, but that can be accounted for.)

Well, around the time last night that the cache was published and the first responders were going after it, I realized that these formulas give a bit of a "back door" around the calculator (which gives the distance between a guess and Yoda's location). Here's how it goes:

7X-2Y+230 and Y^2-7X^2-48339 need to be between 0 and 999. If you use a computing package like Mathematica (which I'm using a lot these days for my multi-variable calculus course), then you can determine that there are only 339 (out of 10^6 !!!) possible locations for Yoda and hence the cache. Here's my code:

z = 0; For[x = 0, x < 1000, x++,
For[y = 0, y < 1000, y++,
If[-1 < 7 x - 2 y + 230 &&
7 x - 2 y + 230 < 1000 && -1 < y^2 - 7 x^2 - 48339 &&
y^2 - 7 x^2 - 48339 < 1000, z++;
Print[z, ": Yoda=", {x, y},
"--> cache=", {7 x - 2 y + 230, y^2 - 7 x^2 - 48339}]]]]

And here's some of the output:

1: Yoda={36,240}--> cache={2,189}
2: Yoda={36,241}--> cache={0,670}
339: Yoda={367,996}--> cache={807,854}

I'd like to figure out how to write a script that exports these coordinates to a KML or GPX file that Google Earth can then plot. I wonder how many of those 339 possible locations correspond to plausible hiding spots? Of course, this is all much more involved than just working with the calculator as intended.

Like I say, geocaching is whatever it means to you. And today, geocaching looks a lot like my job! Time to go grab some LPCs!

Thursday, February 7, 2008

Where's Yoda? calculator

The Where's Yoda? calculator has been moved here.

Wednesday, February 6, 2008

It's not the front page of the Star Tribune, but...

I went to San Diego in January for a mathematics conference, and I was eager to do some caching there, especially since pfalstad and FSU*Noles have several puzzle caches that are duplicated in San Diego and the Twin Cities.

The chairman of my department was also at this conference, and I mentioned to him that I was planning to take an afternoon to rent a car and hike around the hills up by Escondido. It turns out that he grew up in that very area, and he told me that he was interested in coming along for the hike and that he'd be willing to drive.

Now, I don't have a problem advertising my obsession with geocaching. I wouldn't have a blog otherwise, I suppose. But it was with a fair amount of hesitation that I came clean and told him that I was planning to go geocaching. Not always a good idea to reveal an all-encompassing hobby to your boss. Anyway, he said that he was (still) interested in coming along, and it turns out that we had a very nice time. The culmination of our caching route was his finding a plastic lizard with a micro-cache shoved inside, wedged between two boulders, at the top of a significant hike up a rocky hill in the Mission Trails regional park. Good stuff.

Since then, he tells me that he mentions geocaching to lots of people, with a variety of responses. "Oh, I've heard of that." "Why would you want to do that?" In fact, his family puts together a monthly family newsletter, and his geocaching expedition got coverage this month. I know, it's not the Star Tribune, which had an article (discussed in the MnGCA forums) on page one last Sunday about GPSrs and geocaching, but I'll do my small part to spread the good word.

Tuesday, February 5, 2008

The Pathtag Wait is on.

You can see the design of my pathtag above. I ordered it around 1/25, and they say it'll be 4 to 6 weeks before they arrive in the mail.

In the meantime, I have been receiving many pathtags in the mail. You see, when I approved my design, I turned on the Accept Trades button at, and I had 40 within a week. Luckily, these are trusting people, because they have been sending me their tags on the assumption (warranted, I promise) that I will reciprocate when I receive mine. It's a very nice way to distract myself from the fact that I don't have mine yet.

I think I will turn off the Trade button at 50. I ordered 150, and I want to have plenty to place in Twin Cities-area caches and to hand to local cachers.

Let me know if you would like my pathtag!

It was designed by my brother, who is a graphic designer at the Seattle Art Museum. He designs those big lamp post banners that announce big exhibits like "Picasso and friends" (which turns out to be one minor work by Picasso and a bunch of art by people you've never heard of). Let me know if you like what you see and want help designing yours.

Here are the pathtags I have from local cachers:

I found one other tag in a cache: The Fat Cats' pathtag, which I found in FSU*Noles' and pfalstad's San Diego Mastermind cache.

I feel violated.

Last weekend I replaced the cache containers for two of my six cache hides: Plato's Five Gems: Tetrahedron and the final stage of Octahedron. These disappeared almost certainly at the hands of medallion hunters. Grey Wolf told me that lots of medallion hunters were out in Highland Park. This was before the clues started pointing towards Mounds Park.

It turns out that Millah and I were at Mounds Park the weekend before the medallion was found there. (By the way, does anyone know coordinates of the medallion's location? I bet we were close to it without intending to be.) I left with a real sour taste in my mouth for the Medallion Hunt, as you might have guessed if you saw any of my cache logs. I know that many geocachers are medallion hunters (Cooler Crew?), but we came across some pretty surly characters that day. That's what $10,000 does to you, I guess. I imagined having a conversation with someone like this... "You mean you look for stuff that's not worth anything?" "Ah, but the value of a smiley!" :)

So, what happens here? I'm guessing people get excited when they see the container, run back to their car, and when the payload isn't in there, they chuck my lock'n'lock, complete with camo paint, right into the nearest trash can.

On the other hand, I haven't had any geocoins or travel bugs stolen yet, knock on wood, so my Faith In Humanity ratio remains high. Just think if King Boreas lost 1/3 of his caches in one day!

Monday, February 4, 2008

Geocoins are for geocaches.

This weekend a local cacher said in a log that I was brave for activating and putting in a cache my 2007 special edition MnGCA geocoin.

I have to admit that I did hold on to it for a while. But I really wasn't enjoying it as much as I might when it's out traveling around. I love finding geocoins in caches, and I love getting logs on my own coins and bugs. So I want to handle my own small geocoin collection in the same spirit -- by putting them all out there.

We'll see if my tune changes when this or some other coin disappears. (I replaced my first two muggled caches this weekend, so I'm aware of the disenchantment this might create.) But I'm willing to take that risk in order to help create the kind of critical coin-mass in caches that I would enjoy myself.

Why are there only five Platonic solids?

A Platonic solid is a convex polyhedron that has faces that are regular polygons and has the same number of regular polygons around each vertex.

See my series of (four, so far) caches related to Platonic solids: Plato's Five Gems: Tetrahedron, Cube, Octahedron, and Icosahedron. Dodecahedron coming soon!

Let's show that any Platonic solid has to be either a tetrahedron, a cube, an octahedron, a dodecahedron, or an icosahedron.

Let V, E, and F be the number of vertices, edges, and faces of the Platonic solid. Let N be the number of edges of each face, and let M be the number of faces (and hence also edges) around each vertex.

Then we have M x V = 2E and N x F = 2E (in each equation, we're noting that each edge has been counted twice).

Now we have to use Euler's formula: for a convex polyhedron, V - E + F = 2. I'll prove that later on. Substituting V = 2E/M and F = 2E/N, we get

2E/M - E + 2E/N = 2.

Divide both sides by 2E, and we get 1/M - 1/2 + 1/N = 1/E, or 1/M + 1/N = 1/E + 1/2.

Since E is positive, we must have 1/M + 1/N > 1/2, and also M and N have to be at least 3 (do you see why?). The only pairs (M,N) that satisfy these inequalities are (3,3) (tetrahedron), (3,4) (cube), (4,3) (octahedron), (3,5) (dodecahedron), and (5,3) (icosahedron). End of proof.

Now, why is Euler's formula true? There are lots of proofs, but here is one of the easier ones to understand:

Remove one face from your Platonic solid, thinking of it as just the outer skin of vertices, edges, and faces, not the stuff inside. If we can show V - E + F = 1 for that thing, then we will have shown that V - E + F = 2 for the polyhedron.

Imagine flattening that ball with a hole onto a table. That doesn't change V - E + F. Now, one at a time, remove an edge that is on the border and also remove the face that it is next to. E goes down 1, and so does F, so that's a net change of 0 to V - E + F. Continue doing that until you have one polygon left. That polygon satisfies V - E + F = 1, and so the original polyhedron satisfies V - E + F = 2. That proves Euler's formula.