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Thread: Maine Cache and Cache Hider Stats

  1. #21
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    I was going by the depths on the map. Did you use your GPS?

    If it's only -1.5 feet, it may not be the lowest.

    I thought about adding the newest caches, but after thinking about it, I wasn't saure how much value it would have. I'm not planning on updating this on a daily basis.

    I am also pondering a list of Mainers who have placed caches in Maine, sorted by their join date. I could add Non-Placers to the list by hand. But I have mixed feeling about releasing that.


    Quote Originally Posted by tat View Post
    When I placed it, it was exactly -1.9 feet. It's hard to tell what the elevation is today. There is a jetty 8 miles away that is causing beach errosion at Camp Ellis (it's been on the news a lot this week!). All of that sand ends up on my cache! When the sand builds up too much, they dredge it out. So my cache is constantly being built up and torn down.

    How about the newest cache?
    DNFTT! DNFTT! DNFTT!

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  2. #22
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    Quote Originally Posted by brdad View Post
    I was going by the depths on the map. Did you use your GPS?....
    No, I used the tide tables. The lowest tides there are -1.9. The NOAA tide stations are a lot more accurate than my gps.

  3. #23
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    Probably someone already knows this or it's been discussed, but what are the top 10 most found caches in Maine (I imagine the ones that have been around the longest and in more populated or touristy areas would be the leading contenders) . . . and is there a way to find out what caches have the most DNFs (I can't help but think Old 470 would be on that list.)
    "Courage is not the absence of fear, but the realization that there is something more important than fear."

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  4. #24
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    Quote Originally Posted by firefighterjake View Post
    Probably someone already knows this or it's been discussed, but what are the top 10 most found caches in Maine (I imagine the ones that have been around the longest and in more populated or touristy areas would be the leading contenders) . . . and is there a way to find out what caches have the most DNFs (I can't help but think Old 470 would be on that list.)
    and if we counted each of your visits my lombard micro would be second
    Once the game is over, the king and the pawn go back in the same box.

  5. #25
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    Quote Originally Posted by tat View Post
    No, I used the tide tables. The lowest tides there are -1.9. The NOAA tide stations are a lot more accurate than my gps.

    But doesn't the tide chart show how high (or in the case of -1.9 how low) above/below the water depth?

    In other words, in your case, if the depth were 15 feet as I read, you subtract 1.9 from the 15, so the tide would be 1.9 feet lower than the normal low tide? The elevation would be unaffected by the tides, so the elevation of the waypoint would be -15 no matter where the tide was since elevation is referenced to sea level, not tide level. IIRC, sea level is halfway between high and low tides of the ocean.

    That's the way I assumed it was, but I am not sosure now.
    DNFTT! DNFTT! DNFTT!

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  6. #26
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    Elevation is referenced to mean sea level. Tide tables show the difference from mean sea level. So, if the tide table shows the tide height will be 0 feet, then the sea will be at the "mean" at that time. Of course, this assumes the atmospheric pressure is normal, there are no storms at sea raising the level, there is no flooding from nearby rivers, etc. NOAA maintains tide height stations. The data from these calibrated stations is used as a basis for tide charts.

    On the day I placed the cache, I was standing on the ground, in fair weather, with calm seas. The cache rules say to get as close to the water as possible without getting the tops of your feet wet. So, the elevation is very nearly at the level at that time.

    You can use this method to plot the profile of the beach head. Take each gps reading from all of the finders, look up the tide height and that is, by definition, the elevation for that point.

    If your chart was correct, I would have been underwater (-15 - (-1.9) = -13.1 feet)

  7. #27
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    So, the elevation of your waypoint is still, -15 feet, reguardless of the ocean level, correct?


    On the Maine Harbors web site, they say "The tide data on our charts is relative to mean lower low water (MLLW - 0.0') which is the average of the lower (of the two) low water heights of each tidal day. The unit of measurement is feet (and 10ths of a foot)."

    But either way, it still seems to me the water depth on a map is from mean sea level, so that would determine the elevation.

    See what you started by asking for highest/lowest? ;-)
    Last edited by brdad; 04-21-2007 at 07:41 AM.
    DNFTT! DNFTT! DNFTT!

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  8. #28
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    Quote Originally Posted by brdad View Post
    So, the elevation of your waypoint is still, -15 feet, reguardless of the ocean level, correct?


    On the Maine Harbors web site, they say "The tide data on our charts is relative to mean lower low water (MLLW - 0.0') which is the average of the lower (of the two) low water heights of each tidal day. The unit of measurement is feet (and 10ths of a foot)."

    But either way, it still seems to me the water depth on a map is from mean sea level, so that would determine the elevation.

    See what you started by asking for highest/lowest? ;-)
    Yes, it does get complicated.

    How is the elevation of the map defined? If it was defined as the elevation above MLLW, then the elevation of the sand on that day was -1.9. This fact requires the map datum to be 13.1 feet below MLLW, which seems like an odd choice.

    More likely, the water depth on the map is wrong. It may have been correct on the day the map data was collected! Don't forget, the elevation of the sand is constantly changing, so there is no way to keep the map up to date.

  9. #29
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    Yes indeed you fellas have waaaay too much time on your hands...
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  10. #30
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    Quote Originally Posted by tat View Post
    How is the elevation of the map defined? If it was defined as the elevation above MLLW, then the elevation of the sand on that day was -1.9. This fact requires the map datum to be 13.1 feet below MLLW, which seems like an odd choice.
    I beleive the elevation is measure in water depth at mean sea level. Most maps are, as the topozone map shows as well. And I agree, it is bound to change as the sand moves back and forth.

    I'm going to look for an actual nautical map of the area when I get a free minute and see what it says.
    DNFTT! DNFTT! DNFTT!

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