Elevation And Cords.

[backpackermt10]

I'm sort of new at this whole geocaching thing so theres still alot that i dont understand. One question that i have though is, does elevation have an effect on your gps's cooridants, and if it does how do u find out what the elevation for the area that your geocaching in is?

[+Moose Mob]

Ignoring the fact we are on a psuedo-sphere, coordinates are in effect 2 dimensional, or the X & Y coordinates. Look at it as where you are on a printed map. Elevation is the Z coordinate, or height. and has no effect on the coordinates.

 

As far as teh elevaton of where you are headed, you need to view the coordinates on a topomap, such as the ones listed on the cache page, like topozone.

[+fox-and-the-hound]

I agree with the above. The only real effect elevation has had on us has been large land masses (hills, canyon walls, mountain ranges, etc) can sometimes block your line of sight with satellites and give you poor or "bouncing" coords. Otherwise, you should be good.

[+Team Cotati]

If you want to know the elevation for the area that you are IN as you stated, and you have a GPSr which is capable of displaying altitude, and you have four or more satellites locked, then all you need to do is look at the elevation displayed on the screen of the GPSr. Otherwise you will need a map that shows elevation changes along your route of travel. AKA a topology map of the area. You will also need to be able to identify your current location on the map.

Edited January 24, 2006 by Team Cotati

[+Sue Gremlin]

Isn't it fun when you know you are at ground zero, but you also know the cache may also be 200 feet away? 200 above or below you, that is.

 

I have nothing to add to this discussion.

[+Davispak]

Sharp changes in elevation can play havoc with signal and will throw it off some, just as canopy,weather, and time of day. It will only throw it off by about 50 feet at most depending on what you are dealing with and how good a GPSr you have. Heck on perfectly sunny days you can stand in one spot and get a 10 foot fluctuation.

[+JDandDD]

Not sure specifically what you are asking but real, physical elevation no but calculated elevation yes. The GPS tries to calculate its coordinates using the intersection of spheres, basically the intersection of orbital planes of the satellites. With very poor constellations (basically alignments of the satellites) the GPS can have very large errors in the calculations. It tries to place you on the surface of the planet (won't get into the complications but actually the spheres intersect both on the planet surface and at another point in space well above the surface).

 

If there is a sufficiently large error it can report an elevation that is way off and your coords will be way off as well. This happened this past week to me. I had a constellation that was 5 satellites in virtually a straight line from the horizon to the zenith. The best the GPS could do with the errors involved was place me 2500 meters above my actual elevation and about 1.25 kilometers south-south-east.

 

Long winded way to say 'So physical elevation no, but calculated elevation is related'.

 

JDandDD

[+Renegade Knight]

Isn't it fun when you know you are at ground zero, but you also know the cache may also be 200 feet away? 200 above or below you, that is.

 

I have nothing to add to this discussion.

I have been in that situation. Sometimes you just have to flip a coin and follow luck. Then you find it on the side of the cliff you didn't start on.

[+AuntFlora]

Having read all the posts, I still have a question. I am trying to locate a cache which is said to be in a parking structure. Topo maps don't really help here. I went to two different levels at the posted coordinates, but couldn't figure out how close I was because of the different floors. Maybe this is unique to this particular cache, GCRT0N.

[+Team_Talisman]

Having read all the posts, I still have a question. I am trying to locate a cache which is said to be in a parking structure. Topo maps don't really help here. I went to two different levels at the posted coordinates, but couldn't figure out how close I was because of the different floors. Maybe this is unique to this particular cache, GCRT0N.

 

Do this.... take a friend with you, go to top open air parking structure.... Find co ordinates.. Have frind go down one level usually you two can see each other...then you go down one level below friend.....Tell you find cache and get to bottom.....

 

Dave from Team_Talisman

[+Prime Suspect]

Having read all the posts, I still have a question. I am trying to locate a cache which is said to be in a parking structure. Topo maps don't really help here. I went to two different levels at the posted coordinates, but couldn't figure out how close I was because of the different floors. Maybe this is unique to this particular cache, GCRT0N.

There are enough clues in the cache's logs to tell you exactly what the relative elevation is.

Edited April 12, 2006 by Prime Suspect

[+hukilaulau]

Ignoring the fact we are on a psuedo-sphere, coordinates are in effect 2 dimensional, or the X & Y coordinates. Look at it as where you are on a printed map. Elevation is the Z coordinate, or height. and has no effect on the coordinates.

 

As far as teh elevaton of where you are headed, you need to view the coordinates on a topomap, such as the ones listed on the cache page, like topozone.

Am I missing something here? It sounds like you are saying that if I am looking for a cache that might be either on or under a bridge, my gps will register zero on the surface of the bridge even if the cache is 12 feet below. My experience contradicts this. When my gps will not read closer than 12 feet no matter what, I know the cache is either above or below me. Usually it has to be one or the other! Did I misunderstand what you were saying?

[+BigWhiteTruck]

The "coordinates" that we use for geocaching are latitude and longitude.

 

The bottom of a flagpole is at the same latitude and longitude as the top of the flagpole. Going up or down doesn't change your coordinates. In fact, if you imagine a laser beam originating at the center of the earth, shooting up between your feet and out into space, everywhere along that beam is the same latitude and longitude, just vastly different altitude.

 

You could think of your elevation (or altitude) as a third coordinate, in order to describe your location in three dimensions, but it's not useful enough for geocaching because most geocaches are located on the earth's surface, and therefore altitude of the cache is whatever the ground altitude is at that point.

 

In your situation, the cache hider has taken advantage of a unique place when there are multiple altitudes (different levels of the parking garage) at the same coordinates in order to be tricky. What you need to do is find the location at the top level of the parking garage. The cache is either right there, or directly below you (remember the laser beam) on one of the other levels at the same spot.

 

The reason I said to go to the top level of the garage is because that is where your GPS can get the best signal. If your gps got good reception even through concrete and steel buildings, ou wouldn't have trouble using it on each level.

[+Prime Suspect]

Am I missing something here? It sounds like you are saying that if I am looking for a cache that might be either on or under a bridge, my gps will register zero on the surface of the bridge even if the cache is 12 feet below. My experience contradicts this. When my gps will not read closer than 12 feet no matter what, I know the cache is either above or below me. Usually it has to be one or the other! Did I misunderstand what you were saying?

 

Unless your GPS has a built-in altimeter, it's not going to even be able to reliably detect a 12' elevation change. Errors along the Z axis are typically 3× the lat/lon error, so figure it to be in the 40' to 50' range.

 

A GPS reports all distances as if plotted on the surface of the theoretical ellipsoid of whatever datum it's currently set to.

[+lightnsound]

BWT nailed it. Unless the cache hider provides the altitude as additional information in the description, there's no way to know what altitude you are looking for. Therefore it's a moot point.

[+Kryten]

Sometimes caches are deliberately hidden in locations where the geography allows for hiding places at different levels. I've found one in on abandoned railway tunnel that sometimes has people searching the hilltop directly above. Steep cliffs with several paths running across the cliff face can be used in the same way. They make the search more interesting.

[+Lighteye]

Having read all the posts, I still have a question. I am trying to locate a cache which is said to be in a parking structure. Topo maps don't really help here. I went to two different levels at the posted coordinates, but couldn't figure out how close I was because of the different floors. Maybe this is unique to this particular cache, GCRT0N.

 

have run across two of those here in this area, and it took the wife and I a bit to do it through a 5 level parking garage, but we go it.