gps coordinates

[timy]

green trails maps are 1-69500 scale with UTM grids on 2000

meter grids. The question is simple. On green tails maps

what scale (on the UTM card)is used to plot gps co-ordinates, keeping in mind that a UTM card has no scale for maps set at 1-69500

[Mos_Chillin]

Jesus, man. We are simple rock-pullers

[Arc]

lol

[ketch]

I'll give you a hint. In UTM, "U" stands for universal. The location does not change due to map scale.

[timy]

the location does not change to map scale BUT without the

right scale you cannot accurately post a position from a GPS unit onto the map. right? why else would they make a UTM card with 8 different scales?

[tomtom]

Interpolate.

 

Oh, wait. Math is hard and school sucks.

[ketch]

Timy you are right, but you know I can't read TomToms reply without .

 

Here is another hint 1/2 of 2000 =1000, 1/4of 2000=500. I hope you see a pattern here. I would strongly recommend gettin this straight before you try to use your GPS.

 

My experience is that substantial cloud cover, or snow, or a big rock, or ??? can interupt signals enough for the GPS to not be reliable. All the cool toys are nice. I've got some of them but, if your map and compass skills suck there will likley be a day when you are screwed.

 

PS. They make the fancy cards with multiple scales for people that don't want to think on their own or don't want to spend the time. PM me if you want to know an easy way to fashion your own scale for whatever map you might have.

Edited March 20, 2006 by ketch

[gslater]

My experience is that substantial cloud cover, or snow, or a big rock, or ??? can interupt signals enough for the GPS to not be reliable.

 

Hmmmm.... I doubt that. With what kind of GPS did you have this experience?

[timy]

oh gee I THOUGHT this was a site where NEWBIES could come to get information on subjects they have yet to become skilled at. I had no idea this was the whipping post site!!!

[crazyjizzy]

I tried to upload a drawn diagram of how any scale could be used, but i failed. Pick a scale which will numerically divide easily, and hold it at an angle to your grid, such that your two end points land on grid lines. Savy?

[Flatlander1]

Hey Timy:

 

I agree with you about the whipping thing. Green Trail maps appear to be drawn to a unique scale. If you haven't seen it before Maptools has a Green Trails UTM Tool for the 1:69,500 scale.

 

http://www.maptools.com/products/UTM-GT.html

 

Hope it helps, if not you might want to switch to a 1:24,000 USGS map of the same area. It would show more detail and is probably a better map for navigation.

 

Brad

[Mos_Chillin]

oh gee I THOUGHT this was a site where NEWBIES could come to get information on subjects they have yet to become skilled at. I had no idea this was the whipping post site!!!

 

Those are usually related to climbing, since this is a climbers site.

 

Geo-cachers probably wouldn't flame you for your particular request.

 

Welcome!

[iain]

a big rock

 

this can affect the performance of GPS units.

[ketch]

Yes gslater I have experienced challenges with GPS that were weather related. I can not name models off the top of my head but two of them were Garmin units one was a Magellen. It does take a signifiant amount but it does happen. Even when it is not completley lost the signal can be degraded to where position reliabilty is not as good. As to the big rock thing, think large face, if you are at the base you can loose up to half of the sky. If you are in a deep canyon more than half, and hope you never try one from a crevasse or severly restricted sky. Point being that GPS only works well if it can see 3 satelites and preferably four, If a large solid object impairs your view of the sky it don't work so good.

[crazyjizzy]

Hey Timy:

 

 

http://www.maptools.com/products/UTM-GT.html

 

 

Brad

 

Problem solved

[timy]

flatlander thanks much for the info. I do have a 1-24000

usgs map of the area I am interested and can readily plot a gps position on it, but those green trail maps as you've stated are a bit odd and don't conform to any scale. I came to this site because ALL of the people I know including those at the local gear store and REI or its web site had as much info as I already had -0-. Once again thanks!!!!!

[Flatlander1]

Timy:

 

No problem, glad I could help. For what it's worth I take one in the mountains with me but usually only mark waypoints as I'm climbing. We used one on Denali to mark the location of our tent at the 17,200' camp and needed it to find our tent when we got caught in a blizzard. They definetely help but keep up the map and compass skills.

 

Brad

[gslater]

Yes gslater I have experienced challenges with GPS that were weather related. I can not name models off the top of my head but two of them were Garmin units one was a Magellen. It does take a signifiant amount but it does happen. Even when it is not completley lost the signal can be degraded to where position reliabilty is not as good. As to the big rock thing, think large face, if you are at the base you can loose up to half of the sky. If you are in a deep canyon more than half, and hope you never try one from a crevasse or severly restricted sky. Point being that GPS only works well if it can see 3 satelites and preferably four, If a large solid object impairs your view of the sky it don't work so good.

 

Obviously, any situation where you lose your view of a significant part of the sky (cliff, canyon, whatever) will adversely affect the ability of a GPS to accurately determine your position. But when you said "a big rock", I guess I was envisioning a standalone large rock out in the middle of somewhere, not a cliff that blocks your view of the sky.

 

As for weather/snow/etc., I remain very confident that any modern 12 channel receiver won't have much problem determining your location.