Elevation

[Big Brown Cacher]

OK, Ive found a few caches in my area and enjoying it greatly. Quick question on elevation though. 1st: Does the GPSr know how to compensate for extreme elevation changes in reguards to distance? In other words, if Im climbing a really steep mountain where the actual distance is 5 miles up, but on a map in 2D it looks like 3/4 of a mile. Can the GPSr compensate for that and show that I really hiked 5 miles?

2nd question: When entering waypoints for caches, I never see elevations in the description, Do I reset the elevation to zero in all cases urban? I do see in waypoint DLs that the elevation is listed as 0.0 in the ones Ive DLed. Thanx.

 

Me

[+BullDogBob&Double00]

No, It will not compensate for hiking upwards. It is an estimate at best. It is determined by how long it takes signals to reach your GPSr. Also you do not reset the elevation, mine wont even allow you to try. Just bells ans whistles that confuse people.

 

"WITHOUT GEOGRAPHY YOU'RE NOWHERE....Jimmy Buffett

[Kerry.]

No

 

Elevation is not a user configuration except for receivers capable of being configured specifically for 2D but 2D configuration is only suitable in specific instances.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+briansnat]

For units with a barometric altimeter (eTrex Vista and Summit for instance), the user can set the elevation manually. In fact they have to be calibrated from time to time (I do this by flipping to the map screen and walking to a contour line, finding my elevation and using that).

 

Other units use the satellites to determine elevation. On these devices the user can't manually adjust the elevation. BTW, the accuracy of this type of altimeter is poor. I've found it to be off by as much as 200 feet, up or down.

 

"Give a man a fish, he'll eat for a day. Teach a man to fish, he'll sit in a boat and drink beer all day" - Dave Barry

[Nightstalker1967]

If you really 'want' to enter a correct elevation value in your unit you can do it this way. Go to an actual marked benchmark location. Go into setup (the quick start or initiation screen) in your GPS and enter the elevation value of that benchmark. Sit down and record whatever your GPS shows as a value for about 30 minutes. Statistically extract (it helps to take along some type of statistical data recording and reporting device from quality assurance for this) the unit's most consistent reading. COmpare that to the benchmark value. If the values are very close you have a 'correct' value enetered and can quit. If not close enough, in your judgement, reinitiate your unit with a value that is a compromise and recheck. You should eventually get a decent value recorded.

 

I did this on top of Hanging Rock, NC in 1997 when my GPS was new ------- and never used the altitude again....... and now you know 'the rest of the story'........

 

"For the captain had quitted the long drawn strife

And in far Simoree had taken a wife." ( R. Kipling)

[Kerry.]

quote:

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Originally posted by Nightstalker1967:

If you really 'want' to enter a correct elevation value in your unit you can do it this way .... You should eventually get a decent value recorded.

---

 

What GPS receiver are you referring to?

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Nightstalker1967]

What GPS receiver are you referring to?

 

I was referring to a Magellon Pioneer. It was quickly replaced with the Mag.310, I think. But I am not an expert on GPS units. I just took the one I had and did what I wanted to do which included learning its capabilities and limitations. At that time the elevation data was purposely distorted by the government and I wanted to see if I could break their 'code'. Now it is not. At no time have I tried to actually determine how accurate the info is and it has been years since I even paid much attention to elevation on my unit except in a casual way of noticing it because it is there.

 

"For the captain had quitted the long drawn strife

And in far Simoree had taken a wife." ( R. Kipling)

[Kerry.]

At that time all data was purposefully distorted.

 

I got the impression that you thought by entering a "correct" elevation when initializing that this would somehow affect the elevation readings from that point on, BUT that is not the case.

 

All that initial elevation input did (similar with an approx location, date & time) was help the initializing procedure. Once initialized the date/time was fixed from the sats and the position & elevation are separately computed each fix and not connected in any way to those initialize "approximate" (or otherwise) inputs.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+evergreenhiker!]

quote:

---

Originally posted by BrianSnat:

For units with a barometric altimeter (eTrex Vista and Summit for instance), the user can set the elevation manually. In fact they have to be calibrated from time to time (I do this by flipping to the map screen and walking to a contour line, finding my elevation and using that).

 

Other units use the satellites to determine elevation. On these devices the user can't manually adjust the elevation. BTW, the accuracy of this type of altimeter is poor. I've found it to be off by as much as 200 feet, up or down.

 

_"Give a man a fish, he'll eat for a day. Teach a man to fish, he'll sit in a boat and drink beer all day" - Dave Barry_

---

Good idea, Brian,. Hadn't thought of calibrating my Etrex Vista that way.I usually just calibrate at trailheads or at lakes which have a known elevation posted in maps.

[+apersson850]

As previously stated, GPS units calculate distance as if the world is flat, or at least have no hills. For any reasonable slope, it doesn't make any difference that's noticable.

 

On my Vista, the elevation is determined by reading the air pressure. Such a meter has to be calibrated. This can be done by entering the elevation, provided it's known, or by entering the barometric pressure at your position, if you know that pressure. I'm now referring to the pressure at sea level, or rather what it would have been if you were at sea level.

Finally, the third method, which is usually inferior but better than nothing, if you don't know any of the above, is to calibrate to the GPS elevation. The Vista can also do this continiously, to eliminate long time drift due to weather changes.

 

Now, when it comes to waypoints, their elevation is automatically stored with the waypoint, if you store your current position as a waypoint. But when you store some other position, then the elevation is usually not known. If you do it on the Vista directly, it will leave that field blank. If you download a geocache location with EasyGPS, it will set the elevation to zero. You can then manually enter the correct elevation, when you find the cache, or just leave it as it is. It's up to you.

 

Anders