Elevation Effects

[starkat2k]

Hi everyone.

 

I just got my first GPS (A Garmin eTrex Venture, on sale at Galyan's in Salt Lake City for $102), and I'm finally able to really participate in geocaching. But I have a couple of questions. Please help!

 

First question:

How does elevation effect latitude/longitude coordinates?

 

Reason for asking:

I looked up an address on www.geocode.com (the only place I know of to get coords for a street address), and entered it as a point on my Venture. Then, while out making tracks today, I reached the given address, only to find it about 0.6 mile due north of the point I made with my geocode coords.

 

Certainly, the coords could be incorrect, and I bet that they probably are, but I'm also wondering if the elevation will affect the coords as triangulated from the GPS? Here, in SLC, we're at about 4300 feet elevation.

 

Second question:

I see a lot of talk on here about using the compass to pinpoint a cache. Would I have to enter a route into my GPS unit in order to use the compass most efficiently, or is there another way that everyone knows but I haven't figured out yet?

 

I just think entering a route for each trip seems a little cumbersome.

 

Geocaching is something I've wanted to get into for a long time, and I'm happy to be finally able to do it! woohoo!!

 

-starkat

[+bons]

It appears that geocode.com returns coordiates in two formats: Decimal Degrees and Deg:Min:Sec.

 

I'll wager dollars to doughnuts that you're entering one of the two into a gps set for: degrees:minutes.minutes format (ie, those aren't seconds, those are decimal minutes. 30.50 on your GPS is really 30 minutes 30 seconds, not 30 minutes 50 seconds.

 

I've never known or heard of elevation affecting anything. Actually, I've thought about planning a cache that needs elevation in order to solve it properly (perhaps a cache at the right elevation and a micro giving a hint at the wrong elevation) simply because elevation seems to be so rarely used.

 

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

 

There are a few reasons to use a compass:

1) Many gps units don't actually have compasses. They figure out what direction north is by assuming you're walking forward and knowing where you are and where you've been.

2) Those GPS units with electronic compasses don't seem to be nearly as accurate as a $6 brunton.

3) Many of the people here are old school hikers, when a compass and a map was a way of life. Offset caches and other things that need a compass seem natural to them.

[Kerry.]

In simple terms elevation doesn't affect Lat/Long as a point say 10,000 metres vertically (as such) above a ground point of specific lat & long will have the same lat & long.

 

The XYZ coords that the GPS actually determines prior to conversion to a user friendly format (such as lat/long) is a 3 dimensional determination but not quite the same as pure elevation but is what the lat/long & elevation is determined from.

 

Cheers, Kerry.

[+Kewaneh & Shark]

Another cause of your address problem could be that Geocode.com may not have the address system for SLC properly installed in it's database. I know that for the most part, SLC addresses are on a grid-type system, but if there are any anomalies in that system, Geocode.com may not know about it. My town is also set on a similar grid-type system, with one acception - the north-south line that divides the addresses from east side of town and the west side of town has a jog in it - a jog of one mile. My home is inside of that jog and I have yet to find a GPS/address mapping system that can find where I live. I've used Garmins, Magellans, and other third party and internet applications and they all tell me I live a mile east of where I really do.

 

It's doubtful that elevation would have any effect on latitude & longitude. For the purposes of geocaching, any effect would be irrelevant. Just remember that there is an approximate +/- 10 meter error in the coordinate that your GPSr is showing you. The shown elevation has at least that much error as well, possibly more.

 

Some people use a compass when caching when they get to the cache site to pinpoint the cache. When you get very close to the waypoint you're seeking, the compasses or pointer arrows on GPSrs have a tendancy to start to 'spin' and move all over place. Cachers who use traditional compasses will stay outside of that 'spin-zone', let their GPSr settle down and give them a good bearing and distance, align the compass to it and follow it the rest of the way. I've tried using a compass, but one way doesn't help me find the cache any better than the other. I usually just use the GPSr. When the pointer on the GPSr begins to move all over the place, I know that I'm in the right spot. It's time to focus on the GPSr a bit less and focus on looking under bushes and rocks.

 

Good luck on your hunts.