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Include A Way To Test A Coordinate


Iowa Tom
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I just finished a half-hour of juggling a zillion numbers required for determining the coords of a puzzle cache. :P With the hope of finding it I’m going out tomorrow with my son and the new Magellan eXplorist 210 that we gave him this Christmas. I do wish that the cache owner made a way to test the coord before I drive 20 minutes, one way.

 

I myself own some caches that people must calculate the coord for. To reduce the chances of someone’s wasting lots of time and gas, which may occur if they make a mistake, I provide the following information. What you see in Sienna colored letters below is from one of my caches.

 

To test your result, go to this this website and use option 3. In the Source Latitude cell, copy and paste the following coord or type in 42 29.580'N. In the Source Longitude cell place this information: 092 20.580'W.

 

In the Destination cells enter YOUR predicted coordinate. BE SURE TO USE THE EXACT FORMAT as I used above. Use the default Units for results, statue miles, then click on Send Query.

 

A correct answer will read: Distance between 42 29.580'N 092 20.580'W and (your calculated coord) is 1.1997 statute miles.

 

What do you think? Is this something that you think is a good thing to include in certain situations? If you know of any caches that include things like this, please tell us exactly how they word it and to what websites they link you to. I could always write the owner for verification of a coord but may have to wait for days or may never get a response.

 

Thank you for your thoughts!! :P

 

-it

Edited by Iowa Tom
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Just to clarify - normally a checksum is the total of all the numbers in the puzzle coordinates added together (47 34.123 would have a checksum of 24). There's other methods but that's the one I've seen most often.

 

There's a local cacher here who has a website similar to what you describe, except you just put in the GCxxxx code, and your answer, and it tells you if you're correct or not. Nice.

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Lots of puzzle caches use checksums.  This is especially popular in Europe.  A good idea if the owner wants to be helpful.

Until a few months ago, I didn't know what a checksum was; now I are one!

 

15 digit checksum...all puzzle cache pages should include them... maybe there should be a rule, or something! B)<_<

Edited by sept1c_tank
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One reason I use this website is because I want to introduce people to its usefulness.

Why are you so fixated on this particular website? There are lots of places online to calculate distances, and most of those don't use the weird coordinate format of your site.

I will be MORE THAN GLAD to consider another (more user friendly) website that can be used to determine the distance between two coords. Please post the URLs. Thanks!!

 

By the way, I went out this afternoon and spent a significant amount of time and gas $ chasing after what must have been a faulty coord that I came up with. I rechecked my figures over and over before I went out too. NUTS. There was no way for me to test the coord before I took off, hence my reason for bringing this topic up. B)

 

-it

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the trouble with a simple check sum is that it does not correct for a simple transposition error. ...123 adds the same as 132 and that puts you quite a ways off.

 

I will always answer anyone who writes to confirm coordinates.

 

I also did some web searching on how to do a more accurate check sum - used that on one of my caches after a fellow local cacher suggested it.

 

The distance idea is not a bad idea either. It depends on typing in the coordinates correctly and you need two sets. It too does not allow for some errors (on the same radius - different angle with the same distance) but these might be hard to make.

 

cc\

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The distance idea is not a bad idea either.  It depends on typing in the coordinates correctly and you need two sets.  It too does not allow for some errors (on the same radius - different angle with the same distance) but these might be hard to make.

Thanks a bunch for your post cc!

 

The one coordinate (lat & long) I provide. It could be any one but I usually use the fake coordinate or one of the real coords that part of the cache is linked to. I suggest they copy and paste the coord I give to prevent error. It’s up to them to double check the relatively few numbers they have to work with. The real location is always less than 5 miles away from the coord I give them. The odds of someone coming up with a distance that exactly matches the radius I post, like 1.235 miles, is remote.

 

I do a lot of things in my caches that are designed to teach something about what the seeker can use the Internet for. Figuring the distance between to points is one of those things.

 

I hope that someone provides me with one or more distance calculators that are online based (no need for a download) and that are better than the one I mentioned that I use. B)

 

-it

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I will be MORE THAN GLAD to consider another (more user friendly) website that can be used to determine the distance between two coords. Please post the URLs. Thanks!!

Well, I have good new for you! A couple of options exist.

 

First is my program GeoCalc, which is free, gratis, for nothing. It's a Windows executable that does distances and can parse coordinates taken directly off of geocaching.com web pages (actually, it does several other formats, too).

 

Second is the Web page of my friend Boulter, located here. It also sports very user-friendly coordinate entry. Try it!

 

As for verifying coordinates, I have thought about making a Web page where you could enter your puzzle solution coordinates and it would tell you if you were right or wrong. The problem there is that somebody could "brute force" it, by sending thousands of possible solutions until the right one was found. In order to prevent that, I'd have to implement some kind of IP-based throttling, which is a serious pain. So, instead, I try to respond as immediately as I can to any requests for coordinate verification sent me by email.

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HERE is my solution. I don't have the nifty "put it in however you like" type of entry. Mainly, it's because you can only get one wrong answer and then you have to wait an hour. This is so folks don't simply make continuous guesses. The six input boxes help make sure you've got it entered correctly.

 

Later, I might work on a two step process where it will take coords however you want to enter it then asks "are these the coords which you want to check?" before giving an answer. This would help prevent getting hit with an entry error and have to wait an hour.

 

Of course, this only works for puzzles you complete before heading into the field.

 

For one that works well while you're in the field is the simple checksum mentioned above. There is room for error and extrapolating the last digit you need, but it will catch 99% of all errors and prevent a lot of frustration. It's helpful on multis where you go to multiple places and to back track to simply see ifyou made an error would not be fun. With the check sum, you know if you made an error and know you'd have to back track to find it.

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I pulled some "checkum" type information from one of my puzzles becasue it let mathematically clever folks find the cache since I had a maximum radius and several other helpful pieces of info. They narrowod it down to 3 or 4 possible spots and searched them exhaustively...

 

Now I just encourage my seekers to contact me if they want a hint or confirmation.

 

Paul

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Thanks for the replies.

 

I didn't know I got any for a while because, even though I am supposed to get an automatic notification, I often don't. I clicked on Track this topic and got the usual, " You are already subscribed to this topic or forum."

 

I finally figured out the puzzler cache which precipitated this discussion. The owner is very busy and does not answer mail in a timely manner so I got some help from a friend that already found it. He helped me to see my errors. I was only about 20 miles off! I was searching in a wooded area along a creek in Amish country. :antenna:

 

Now can someone lead me to a URL that shows how to do the check sum.

 

Thanks!

 

-it

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I didn't know I got any for a while because, even though I am supposed to get an automatic notification, I often don't. I clicked on Track this topic and got the usual, " You are already subscribed to this topic or forum."

I don't know if this has anything to do with it:

 

There may be more replies to this topic, but only 1 email is sent per board visit for each subscribed topic. This is

to limit the amount of mail that is sent to your inbox.

 

We now return you to your regularly scheduled topic...

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To sum things up, I'm not familiar with checksum. Can sumbody please provide an actual worked out example by summarizing the technique. B) I would like to see a link to an actual cache, w/o actually giving away any real summations of course. [i have read about it now but I suspect that somebody out there can breath some life into the concept.] Also, how about an example of a Digital Root along with a cache that uses it. :lol:

 

Thanks for the summary.

 

-it (= -1 * the sum of i + t)

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To sum things up, I'm not familiar with checksum. Can sumbody please provide an actual worked out example by summarizing the technique.

Around here, people usually just give the sum of the digits in the cache coordinates. So, for example, the checksum for

 

N 37 49.537, W 121 48.825

 

would be

 

3+7+4+9+5+3+7+1+2+1+4+8+8+2+5 = 69.

 

Sometimes people give the sum of the lat and long separately.

 

There's also the "digital root" where you take the checksum described above and add its digits together to get a new number, repeating as necessary until you have a single digit. The result is just a simple function of the number:

 

DR(n) = 1 + [(n-1) % 9]

 

where % is the mod operator.

 

I've been thinking about adding a tab to GeoCalc that will calculate checksums from coordinate strings for you. Would that be useful to anyone? Since I am presently unable to cache for a couple weeks (I hurt myself yesterday) it's a fine opportunity to add new features...

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Thanks fizzymagic for the enhancement now available to us.

 

I think I will add a link to your program in some of my ccahes as another option for testing the final coordinate that a player comes up with.

 

A hour ago my son and I finally found the puzzler that initiated my starting this thread. I will contact the owner and tell him about the various check options.

 

-it

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now, only question....whos calculator is most accurate?

What / who is the standard?  distances etc?

To me absolute accuracy is not the issue (unless I am trying to determine whether two places are closer than the minimum distance allowed between caches, or parts of a multi, that being 0.1 mile).

 

Consistency (precision) is most important.

 

-it

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now, only question....whos calculator is most accurate?

What / who is the standard?  distances etc?

The "high accuracy" mode in GeoCalc uses the Vincenty method for calculation of the geodesic distance. It's mathematically the most accurate method around, good to a few millimeters over several thousand miles. You will get exactly the same answer with pretty much any website, since they tend to use the same algorithm and the same ellipsoid (GeoCalc uses the WGS84 ellipsoid).

 

But even though the algorithm is very accurate, the results aren't exactly Gospel. That's because the actual distance depends on things you don't know. For example, most implementations of Vincenty's method assume that the points are exactly on the ellipsoid; in real life, they will be at some elevation above sea level, and sea level isn't even exactly on the ellipsoid anyway because of variations in the gravitational force from variations in the density of the Earth's crust.

 

GeoCalc also allows you to do the calculations using the Great Circle method, which approximates the Earth as a sphere instead of an ellipsoid. Those calculations are less accurate.

 

And it allows you to calculate distances along a "rhumb line," which is a path of constant heading. Rhumb lines are actually spirals, but they are useful for navigation.

 

Bottom line: geodesy (measuring distances on the Earth) is a very complicated subject. Use the high-accuracy mode of GeoCalc and it will give you answers plenty accurate for any geocaching purpose you'll ever have.

 

Oh. And one more thing: download the newest version of GeoCalc from here. I found a little bug where it wouldn't parse the coordinates copied straight from this site properly. The newest version is 0.9.21.

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I will be MORE THAN GLAD to consider another (more user friendly) website that can be used to determine the distance between two coords. Please post the URLs. Thanks!!

Well, I have good new for you! A couple of options exist.

 

First is my program GeoCalc, which is free, gratis, for nothing. It's a Windows executable that does distances and can parse coordinates taken directly off of geocaching.com web pages (actually, it does several other formats, too).

 

Second is the Web page of my friend Boulter, located here. It also sports very user-friendly coordinate entry. Try it!

Thanks for the link. I use GeoCalc on my PC since it is more handy than a web site and as you say the coord input is user friendly. But there are times I like a web page converter, for example when I am using someone else's PC. I noticed that your friend's page does not calculate the bearing angle between the two points and does not display in feet. I recently put up a cache that required geometric calculations to find the final stage. Getting the results in feet and the bearing angles were crucial to being able to place or hunt this cache.

 

Just a sugestion.

 

As for verifying coordinates, I have thought about making a Web page where you could enter your puzzle solution coordinates and it would tell you if you were right or wrong.  The problem there is that somebody could "brute force" it, by sending thousands of possible solutions until the right one was found.  In order to prevent that, I'd have to implement some kind of IP-based throttling, which is a serious pain.  So, instead, I try to respond as immediately as I can to any requests for coordinate verification sent me by email.

 

Personally, if someone wants to find a cache this way, I feel let 'em. It's not like they get a prize or anything.

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fizzymagic,

 

I should have read the rest of the thread before replying. I didn't realize that you had written GeoCalc. It is a great program! The only complaint I have is that it is hard to find on the web. If I do a google search on GeoCalc I get a lot of commercial programs. You might consider giving it a more unique name like GeoCalc Plus or something.

 

I found it truely invaluable in setting up Thales' Theorem. I had to do a lot of calculating and checking of coordinates since I couldn't just place the cache and design the problem around it.

 

One problem I have a work is that they don't allow us to run any executables that have not been "approved". So I could not use GeoCalc at work (where the cache is). Is there a way to port GeoCalc to the Palm or possibly support some form of code that could run on my work machine, like JAVA perhaps? Although I am an engineer, I may be showing my ignorance on this. I do embedded stuff and have not had to learn how JAVA or similar byte code languages work.

 

I may be getting Forth installed soon on my work PC as a hardware check out tool. That should provide a framework for me to run programs that are not "blessed" by the PTB. Any chance your program is in Forth?

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