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# Re: Most impressive challenge idea?

Re: Most impressive challenge idea? January 10, 2018 05:05AM |
Registered: 4 years ago Posts: 58 |

Adding another challenge idea to the main one being discussed here:

This is from fizzymagic and is the "well traveled cacher challenge".

His idea is the cacher must find 6 caches such that the area of the polygon formed by those 6 caches is greater than 10% of the Earth's total surface.

The idea was discussed at some length in the Geocaching.com forums. fizzy got so far as doing a python implementation of a checker but no lua one exists. Offhand, I can't think of how this challenge would violate the challenge guidelines. No time limits, no explicitly defined polygon bounding where the caches must lie, etc. Any violation you can think of?

A sample of the output from his python checker is here in the thread:

https://forums.geocaching.com/GC/index.php?/topic/339949-challenge-cache-ideas/&do=findComment&comment=5615310

Locally we likely have 10 cachers that could qualify such a challenge.

This is from fizzymagic and is the "well traveled cacher challenge".

His idea is the cacher must find 6 caches such that the area of the polygon formed by those 6 caches is greater than 10% of the Earth's total surface.

The idea was discussed at some length in the Geocaching.com forums. fizzy got so far as doing a python implementation of a checker but no lua one exists. Offhand, I can't think of how this challenge would violate the challenge guidelines. No time limits, no explicitly defined polygon bounding where the caches must lie, etc. Any violation you can think of?

A sample of the output from his python checker is here in the thread:

https://forums.geocaching.com/GC/index.php?/topic/339949-challenge-cache-ideas/&do=findComment&comment=5615310

Locally we likely have 10 cachers that could qualify such a challenge.

Re: Most impressive challenge idea? January 10, 2018 05:09AM |
AdminRegistered: 4 years ago Posts: 629 |

rragan Wrote:

-------------------------------------------------------

> The idea was discussed at some length in the

> Geocaching.com forums. fizzy got so far as doing a

> python implementation of a checker but no lua one

> exists. Offhand, I can't think of how this

> challenge would violate the challenge guidelines.

> No time limits, no explicitly defined polygon

> bounding where the caches must lie, etc. Any

> violation you can think of?

>

I can't think of a reason either. It's more or less the same as saying log 2 caches with X km/miles apart. But it's 2 dimensional instead of 1 dimension.

-------------------------------------------------------

> The idea was discussed at some length in the

> Geocaching.com forums. fizzy got so far as doing a

> python implementation of a checker but no lua one

> exists. Offhand, I can't think of how this

> challenge would violate the challenge guidelines.

> No time limits, no explicitly defined polygon

> bounding where the caches must lie, etc. Any

> violation you can think of?

>

I can't think of a reason either. It's more or less the same as saying log 2 caches with X km/miles apart. But it's 2 dimensional instead of 1 dimension.

Re: Most impressive challenge idea? January 10, 2018 07:40PM |
Registered: 3 years ago Posts: 764 |

> His idea is the cacher must find 6 caches such

> that the area of the polygon formed by those 6

> caches is greater than 10% of the Earth's total

> surface.

>

> Locally we likely have 10 cachers that could

> qualify such a challenge.

I opened that thread and at first clance, I think that it needs a better definition. Calculating 10% area from the surface of the geoid (=Earth) is not so easy at all. Calculating area of polygon at a plane is easy but frankly, there is no straight line in this calculation if it goes right. (:P) The worse part may be the fact, that the checker must find those six caches which construct the largest area from all finds. The largest area from 0% - 50% range is achieved by selecting six caches from the same great circle. Any six caches from the same great circle gives area which is 50% of total area. So... the nearest straight power trail with at least six caches will do this. :D

> that the area of the polygon formed by those 6

> caches is greater than 10% of the Earth's total

> surface.

>

> Locally we likely have 10 cachers that could

> qualify such a challenge.

I opened that thread and at first clance, I think that it needs a better definition. Calculating 10% area from the surface of the geoid (=Earth) is not so easy at all. Calculating area of polygon at a plane is easy but frankly, there is no straight line in this calculation if it goes right. (:P) The worse part may be the fact, that the checker must find those six caches which construct the largest area from all finds. The largest area from 0% - 50% range is achieved by selecting six caches from the same great circle. Any six caches from the same great circle gives area which is 50% of total area. So... the nearest straight power trail with at least six caches will do this. :D

Re: Most impressive challenge idea? January 10, 2018 10:48PM |
Registered: 4 years ago Posts: 58 |

I think he assumed a polygon on a planar earth projection. Farthest NSEW finds would give 4 bounds Then picking two more gets interesting. If the first 4 are over 10% you could almost call it quits. Failing that, most NE,NW,SE,SW would be tried for the best two I guess. Current stats already list most northerly, easterly, etc. If those are "free", that could save time.

Re: Most impressive challenge idea? January 10, 2018 11:13PM |
Registered: 3 years ago Posts: 764 |

rragan Wrote:

-------------------------------------------------------

> I think he assumed a polygon on a planar earth

> projection. Farthest NSEW finds would give 4

> bounds Then picking two more gets interesting. If

> the first 4 are over 10% you could almost call it

> quits. Failing that, most NE,NW,SE,SW would be

> tried for the best two I guess. Current stats

> already list most northerly, easterly, etc. If

> those are "free", that could save time.

This is exactly what I mean. At the beginning, the tasks seems to be simple, but then more and more exceptions and additional terms, just because it does not work otherwise as was thought.

To be correct from the beginning, the challenge should start from requesting 10% area of rectangular world map in specific projection to be covered, not the surface of Earth. Then we can build a single convex hull covering all finds and then find all subsets of any arbitrary number of caches quite easily to find the largest. It is possible to cover the map from 0% to 100% with this kind of rules. The checker script needed for this kind of challenge is possible. You only have to request it for you challenge.

ps. I suggest Mercator projection because it is easiest (=only) to visualize in the checker.

Edited 2 time(s). Last edit at 01/10/2018 11:19PM by arisoft. (view changes)

-------------------------------------------------------

> I think he assumed a polygon on a planar earth

> projection. Farthest NSEW finds would give 4

> bounds Then picking two more gets interesting. If

> the first 4 are over 10% you could almost call it

> quits. Failing that, most NE,NW,SE,SW would be

> tried for the best two I guess. Current stats

> already list most northerly, easterly, etc. If

> those are "free", that could save time.

This is exactly what I mean. At the beginning, the tasks seems to be simple, but then more and more exceptions and additional terms, just because it does not work otherwise as was thought.

To be correct from the beginning, the challenge should start from requesting 10% area of rectangular world map in specific projection to be covered, not the surface of Earth. Then we can build a single convex hull covering all finds and then find all subsets of any arbitrary number of caches quite easily to find the largest. It is possible to cover the map from 0% to 100% with this kind of rules. The checker script needed for this kind of challenge is possible. You only have to request it for you challenge.

ps. I suggest Mercator projection because it is easiest (=only) to visualize in the checker.

Edited 2 time(s). Last edit at 01/10/2018 11:19PM by arisoft. (view changes)

Re: Most impressive challenge idea? January 11, 2018 12:24AM |
Registered: 4 years ago Posts: 58 |

Re: Most impressive challenge idea? January 11, 2018 12:38AM |
Registered: 3 years ago Posts: 764 |

rragan Wrote:

-------------------------------------------------------

> Fizzy suggested the Hobo-Dyer projection as

> reducing computational costs. See linked post in

> thread. I appreciate only Mercator mapping is

> supported.

I saw this but it is not true. It is true that in this Hobo-Dyer projection you can compare objects by size directly, but lines are not straight and sides of surface polygons are converted to curves same way as Mercator projection does.

It is much easier, if we start by defining polygons only on the rectangular map plane and not on the earth surface at all. All straght lines on map plane are curves on Earth surface, but who cares if it looks interesting on map ;)

-------------------------------------------------------

> Fizzy suggested the Hobo-Dyer projection as

> reducing computational costs. See linked post in

> thread. I appreciate only Mercator mapping is

> supported.

I saw this but it is not true. It is true that in this Hobo-Dyer projection you can compare objects by size directly, but lines are not straight and sides of surface polygons are converted to curves same way as Mercator projection does.

It is much easier, if we start by defining polygons only on the rectangular map plane and not on the earth surface at all. All straght lines on map plane are curves on Earth surface, but who cares if it looks interesting on map ;)

Re: Most impressive challenge idea? January 11, 2018 09:35AM |
AdminRegistered: 4 years ago Posts: 629 |

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