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Thread: Physical boundaries vs GIS boundaries

  1. #1
    Moderator LuJon's Avatar
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    Default Physical boundaries vs GIS boundaries

    Some time back I was running my sled down the Rex trail and I noticed that the trail on my fancy mapping GPS machine was several hundred feet frome the actual physical trail. This got me wondering, The regulations used the trail as a boundary. Should it be the physical trail or the documented trail in the GIS records? If the trail is the boundary and there is a moose ahead on the north side of it about 25'. Lets suppose he is a legal moose on the south side of the trail. If the GIS map shows that the trail is suppose to be 500' further to the north than it is physically located is that a legal moose or not? It would seem that it could be argued that the moose was actually 475 feet to the south side of the true surveyed boundary. It would seem that the latest GIS survey should be the standard as those boundaries do not move unlike a trail which is constantly changing and branching out.

    So what do you think true GIS or physical boundary, which one matters? Or is there a bunch of grey area moose we shouldn't shoot for fear of having out guns and hunting rights taken away?

  2. #2

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    A land surveyor once told me that where there is a discrepancy between the description and the actual physical location of a corner or or other monument, the actual physical location takes precedence.
    The issue of the trail moving over time would be the same as when a river is used as a boundary for a GMU. Rivers move over time, but regardless of whether or not your GPS is working you can always just open your eyes and see where the boundary is on any given day.
    I hope we don't ever arrive at the point where we have to take all sorts of electronic techno gear into the field in order to make sure that we're legal.
    Mark

  3. #3

    Default If I were sure

    1. That the same agency that is busting me has defined the "line" in a GIS format.
    2. They used the same datum set as my GPS.
    3. I have my shooting position plotted and ditance and azimuth to the moose (to show I have good cause to believe it was within the huntable area when I shot)
    4. I had all this data crosschecked on a backup GPS.
    5. And I knew the trooper would not confisticate my GPSs containing my proof as evidence......

    I would still let it walk, I have a real problem with boundaries as lines on a map. We have enough trails, roads, rivers and drainages to closely enough define areas, boundaries we can actually see. Outdoor activities are supposed to be simpler and enjoyable I thought.
    Mike
    Mike
    www.alaskaatvclub.org
    There is a faster way off the mountain, might hurt a little though.

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    Default

    I have to agree with Mike. I've done survey work with the BLM here in AK. The maps are usually NAD27 AK Datum, from the 1970's. Your GPS, if stock will have a WGS84 Datum set as the default and unless you change it, and most people won't know that minor detail.

    There is a large difference between WGS84 & NAD27 datums, depending on the location, a 1/2 mile or more; but a couple hundred feet is normal and is what I believe you are seeing on your screen.

    I also do Search and Rescue in Fairbanks, we have all of our primary units set to NAD27 to correlate with the maps, when we get a GPS reading for an injured person (from plane or ground), we set a backup unit to WGS84 to be able to check BOTH locations. In dense forest, that difference will prevent you from finding the person if you don't check them both. We have found that 95% of the people who use GPS leave it to default settings.

    Let the moose walk, it isn't worth the fight you would have to do to keep it.

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    Default

    I agree with blybrook. I too think that you are seeing the dfference between nad27 & wsg84. F&G list their areas using wsg84 which they note in the regs when they list a boundary using long/lat and as said the topo maps use nad27. Also note that if you use google earth be sure you are using the same systems.

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    Default Playing With Fire

    Can you imagine trying to justify to ANYBODY (let alone a trooper) how you thought you were justified in shooting a moose on the wrong side of a trail when the tracks from your sled/ATV clearly came from the real trail a few hundred yards away? He/she would laugh you out of the forest when your "imaginary" trail didn't show up on the "real" earth.

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    Thanks for the lesson on nad and wgs. greatly appreciated. J.

  8. #8
    Moderator LuJon's Avatar
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    Default

    Quote Originally Posted by Cazador View Post
    Can you imagine trying to justify to ANYBODY (let alone a trooper) how you thought you were justified in shooting a moose on the wrong side of a trail when the tracks from your sled/ATV clearly came from the real trail a few hundred yards away? He/she would laugh you out of the forest when your "imaginary" trail didn't show up on the "real" earth.
    Lets flip the scenario. Can you imagine getting busted for shooting a moose that was on the right side of the "real" trail but the wrong side of the GIS boundary?

    I also appreciate the info on the multiple GPS standards! Makes me wonder how many people are building cabins a couple hundred feet from their remote property

  9. #9
    Member martentrapper's Avatar
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    Quote Originally Posted by LuJon View Post
    true surveyed boundary. ?
    Now there's some wording a couple lawyers could argue over!
    Has the Rex trail been "surveyed"?
    I would think the wording of the reg would dictate where the line is. Without a legal requirement to have a GIS/GPS instrument, the line would be a physical line.

    Some CUA's have partial boundaries that are straight lines between points. One could have actual need of GIS info and units in that situation.
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