Question about compass's & google earth

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Brad
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Question about compass's & google earth

Postby Brad » Thu Aug 30, 2012 2:53 pm

How far off is north from magnetic north? If I want to make maps off google earth and print out and laminate, will my compass be accurate at getting me to where I want to go to scout or hunt? When you have north on google earth, is it true north or magnetic north? I also read something about maps having declination differences, what is that all about?


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Re: Question about compass's & google earth

Postby Bowhunting Brian » Thu Aug 30, 2012 6:43 pm

I believe magnetic north will be off more the further you are from the north pole. I also think a compass is accurate enough for most hunters. the only time I think it would really factor in is if you were trying to fing an exact spot.
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Re: Question about compass's & google earth

Postby Crazinamatese » Thu Aug 30, 2012 10:16 pm

Pages 57-71 in this link can answer some of your questions.
http://www.uvm.edu/~goldbar/FM3_25.26.pdf
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Re: Question about compass's & google earth

Postby jlh42581 » Thu Aug 30, 2012 11:18 pm

Bowhunting Brian wrote:I believe magnetic north will be off more the further you are from the north pole. I also think a compass is accurate enough for most hunters. the only time I think it would really factor in is if you were trying to fing an exact spot.


This answer is spot on. I worked in GIS for a few years. Think of the meridian lines and the equator. As you get closer to the equator they get wider apart. What this creates is an off shaped rectangle that constantly changes.

With a topo/aerial youll be plenty close enough. The only time it wont work would be over a heavy iron deposit.
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Re: Question about compass's & google earth

Postby Southern Man » Thu Aug 30, 2012 11:53 pm

Brad Lamont wrote:How far off is north from magnetic north? If I want to make maps off google earth and print out and laminate, will my compass be accurate at getting me to where I want to go to scout or hunt?


I have no problem at all finding exact spots I want to go using a compass and topo. Learning to watch the terrain and topo map is probably more important than relying on the compass for exact direction. Not saying the compass is not needed, it is, but only as reference for direction, even tho it may vary a bit.
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Re: Question about compass's & google earth

Postby Brandon » Fri Aug 31, 2012 2:43 am

I use google earth on my phone. blue dot tells me where Im at, and it changes to an arrow when I move to tell which direction im going.
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Re: Question about compass's & google earth

Postby headgear » Fri Aug 31, 2012 3:00 am

I have walked for miles pretty much blind except for an aerial photo and compass and I have always been able to find my location. You might end up to the side but I alwasy find the general area I am looking for. If you are going in blind for a hunt give yourself a little extra space so you don't accidentally show up in the wrong spot and your scent is blowing into the bedding area. Also walking out in the dark can be a little more challenging, trust your compass and expect to come out in a different location than your plan on. For way back locations I alwasys like to scout them first before I hunt.
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Re: Question about compass's & google earth

Postby natvbearhntr » Fri Aug 31, 2012 3:28 am

I used to walk blind then I got lost, then I walked in circles, then I bought a compass and didn't believe it was telling me to go in the right direction and again got lost, then I bought a GPS now I follow the line in and follow the line out. lol
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Re: Question about compass's & google earth

Postby Exophysical » Mon Dec 09, 2013 5:54 pm

natvbearhntr wrote:I used to walk blind then I got lost, then I walked in circles, then I bought a compass and didn't believe it was telling me to go in the right direction and again got lost, then I bought a GPS now I follow the line in and follow the line out. lol


I've got both and I would never consider a GPS an alternative to a compass, a handy addition but never a substitute. I once tracked a deer a long ways and used my GPS to get back to the truck, highly frustrating to say the least. Regardless of what the claims are they can not reliably tell direction unless one is moving, at the pace of a human bushwhacking through heavy timber you need to go a fair distance off course before it shows up on the GPS. If you like walking 3 miles of zig zags to go 1 mile then a GPS for general navigational purposes is great ! :D
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Re: Question about compass's & google earth

Postby ihookem » Sat Nov 29, 2014 2:28 pm

In Wisconsin m magnetic north isn't off by more than a few degrees. I can't walk nearly that straight in the woods.
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Re: Question about compass's & google earth

Postby Farrier » Wed Dec 10, 2014 3:10 pm

Go to the USGS website, find the area you want to map, use the "navigate" radio button to move around, then zoom in and use the "mark points" map tag,

LINK to USGS map site!

Once you have zoomed in to the point that the site puts named rectangles over the map you want, your can change from the "Navigate" to the "Mark Points", left click on each rectangle and leave a map mark on each one, then right click on each map mark, and select to either buy the map, or to download it. Download it as a zip file, once it is downloaded to your computer, extract the file from the zip file, you can now view the map in Adobe Acrobat.

At the bottom of that map is the declination. in looks like the image below, but the angle will be different.

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As you can see there is over 11° difference from Grid North to Magnetic North, on this map. When you know the declination you can set your compass, so that all bearings that you take, can be transferred to and from the map to the real world and back again.

Just checked Northern WI and it's 2.5° West of North.

Hope that helps!
Last edited by Farrier on Wed Dec 10, 2014 3:31 pm, edited 1 time in total.
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Re: Question about compass's & google earth

Postby Swampbuck » Wed Dec 10, 2014 3:22 pm

Brandon wrote:I use google earth on my phone. blue dot tells me where Im at, and it changes to an arrow when I move to tell which direction im going.


This or a gps app is the way to go. Compass and map are good to know how but new phones make it a snap. Even with no service.

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