# True Distance?

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I hope I am able to ask this question so it makes sense as to what I want to know . We have been discussing for quiet some time now as to whether the gps distance readings are accurate when going on hikes that include a lot of climbing in elevation and descending. The best way I can describe what I am asking is to put it in an exaggerated question---if you had a ladder that extended vertical for lets say 1/2 mile---and climbed it, would the gps show that you had in fact traveled 1/2 mile even though you were traveling vertical instead of horizontal? Hope someone can answer this question . Thanks--Yankeeboy4

The GPS measures distance horizonitcaly (I know I didn't spelel that right) or as the crow flies. To give you an example using a real cache hidden in a 5 story parking garage. It would tell you that you were within 20 feet...but not on what level.

Any cacher that caches in the mountains will tell you that the distance given on the GPS is very decieving. It dosen't take into account the winding trails or the elevation climb.

Hope that helps.

El Diablo

Edited by El Diablo

It seems like a lot of caches that say one mile are three miles. One horizontally and two straight up.

It seems like a lot of caches that say one mile are three miles. One horizontally and two straight up.

...Or straight down!

horizonitcaly

Spell it right? I think you made it up.

I think that everyone is missing the point of yankeeboy4's question. He is not asking about the calculated distance to a waypoint according to the GPS. He is asking if he walks from one point to another and uses the distance tracking feature of the GPS will it be the true distance. I believe the answer is YES. RM

if you had a ladder that extended vertical for lets say 1/2 mile---and climbed it, would the gps show that you had in fact traveled 1/2 mile even though you were traveling vertical instead of horizontal? Hope someone can answer this question  . Thanks--Yankeeboy4

No the distance traveled would be Zero, but the altitude will change .5 miles

(if we disallow that most GPSr's Altitude readings are not accurate)

That's his question but not the right answer. If you did a hike that consisted of a one mile flat walk, then climbed straight up a ladder which was half a mile high your GPS would say that you have moved one mile. Your GPS measures trip distance horizontally. Some models will track elevation gain or loss but it is not part of your horizontal distance travelled.

It all depends on the model being used for the calculation. (geodetic model - not the equipment) The 'flat earth distance' would be one mile, the straight line distance would be (flat earth model) 1.1180339887498948482045868343656 miles(ish) while the actual distance traveled (again, flat earth) would be 1.5 miles.

If you wish to include curvature parameters and other complications (not very relevant in this sort of distance) then it all changes.

I know the Garmin vista has such features as vertical speed to destination. It uses a barometric altimeter in conjunction with the gps vertical position. I'm not sure if it does indeed include vertical distance in it's estimation of your distance to a given point, however. Anothr point worth noting is that using the GPS as a speedometer while ascending a steep incline might render the speed reading inaccurate.

horizonitcaly

Spell it right? I think you made it up.

That made milk spurt out my nose, thanks!

.... if you had a ladder that extended vertical for lets say 1/2 mile---and climbed it, would the gps show that you had in fact traveled 1/2 mile even though you were traveling vertical instead of horizontal?

The uncomplicated (theoritical) answer in GPS distance terms is zero (0). If the GPS was capable of accurate vertical representation then it would show a difference in height of 0.5 miles but the lat/Long would be unchanged (in the true vertical sense).

Cheers, Kerry.

(if we disallow that most GPSr's Altitude readings are not accurate)

I have to agree with CO. Just at my own musings I decided to record what my GPS altitude was recording at benchmarks compared to what was posted on the web post. Now granted I've only found 2 benchmarks but in both cases the elevation was 10-80 feet different than the posted elevation. Does this really matter? Not in this case just an interesting tidbid.

Edited by cutsandbruises
horizonitcaly

Spell it right? I think you made it up.

LMAO!!

El Diablo

I hope I am able to ask this question so it makes sense as to what I want to know . We have been discussing for quiet some time now as to whether the gps distance readings are accurate when going on hikes that include a lot of climbing in elevation and descending. The best way I can describe what I am asking is to put it in an exaggerated question---if you had a ladder that extended vertical for lets say 1/2 mile---and climbed it, would the gps show that you had in fact traveled 1/2 mile even though you were traveling vertical instead of horizontal? Hope someone can answer this question . Thanks--Yankeeboy4

At last, I have the answer . I cantacted Garmin with the same question, and the following is Garmins responce!

Thank you for contacting Garmin International,

I'd be happy to help with that. The trip computer will take accent and

descent into account. Before a trip clear it out and the distance shown

there will include ascent and descent. When you initiate a GOTO the distance

shown there is purely horizontal.

Best Regards,

Don Olsen

Product Support Specialist

GARMIN International

800-800-1020

http://www.garmin.com

Fax 1-913-397-0836

All of you that replied, thanks ---Thought you might be interested in Garmins answer.

I think that everyone is missing the point of yankeeboy4's question. He is not asking about the calculated distance to a waypoint according to the GPS. He is asking if he walks from one point to another and uses the distance tracking feature of the GPS will it be the true distance. I believe the answer is YES. RM

That will teach all of you to trust a Rocket Scientist!

Actually, I did not know for sure, but I suspected that the trip computer took accent and descent into account based on my experience with my Vista.

Rocket Man

The trip computer will take accent and descent into account.

That's funny. What the H does "take into account" mean?

Before a trip clear it out and the distance shown there will include ascent and descent.

Seems to imply that the the distance recorded by the trip computer is the hypoteneus of the horizontal/vertical triangle. I would be EXTREMELY surprised if that were the case as land measurements are by convention and common sense always measured horizontally. In practical terms (normal topography), if you were measuring elevation changes accurately (yeah right) it wouldn't make much difference because all but the steepest routes a person is likely to take on the Earth are nearly flat horizontal. I'll go out on a limb here and suppose that this "Product Support Specialist" is either sadly misinformed, or makes up answers when he doesn't know the right one. Still, I suppose it's possible that the Garmin engineers decided that consumers, believing that distances are measured along the undulating surface of the Earth, need to have their GPSRs measure them that way.

Where's the shaking head smiley when you need it?

The trip computer will take accent and descent into account.

That's funny. What the H does "take into account" mean?

Before a trip clear it out and the distance shown there will include ascent and descent.

Seems to imply that the the distance recorded by the trip computer is the hypoteneus of the horizontal/vertical triangle. I would be EXTREMELY surprised if that were the case as land measurements are by convention and common sense always measured horizontally. In practical terms (normal topography), if you were measuring elevation changes accurately (yeah right) it wouldn't make much difference because all but the steepest routes a person is likely to take on the Earth are nearly flat horizontal. I'll go out on a limb here and suppose that this "Product Support Specialist" is either sadly misinformed, or makes up answers when he doesn't know the right one. Still, I suppose it's possible that the Garmin engineers decided that consumers, believing that distances are measured along the undulating surface of the Earth, need to have their GPSRs measure them that way.

Where's the shaking head smiley when you need it?

Hmmmm---your right---where is the shaking head when you need it. For in your case, you won't believe the facts when presented to you. Thats ok---I am happy with the answer I received from GARMIN.

Sorry for the typos in my above post. the Rhino-virus made me do it.

you won't believe the facts when presented to you.

Facts and belief are mutually exclusive concepts. Your happiness in no way affects the validity of statements presented as facts, especially by a 'Product Support Specialist' (read minimum wage help-desk drone with a script). Sorry, that wasn't fair. Don Olsen might be a straight-up, competent fellow with a real interest in GPS, but the job qualifications for answering an 800 line, or answering emails from consumers of sub \$1000 products do not include any technical background at all. The technical training for these jobs mostly consists of reading a manual containing little more than FAQs on the products being supported.

I happen to think the Garmin guy was right, but easily checked out. Reset the trip odometer, attatch a line the the wrist strap of the GPS, lower it over a bridge, and raise it back up. Read the trip odometer. Will not take too much distance to show a reading.

Wouldn't your track log profile also suggest that the GPS takes distance into account when dealing with elevation?

These "facts" can indeed be checked, validated or whatever (I think anyway) in a practical sense. It will however take a few days to log enough relevent data to make some assumptions.

It's an interesting theory and as always one must not jump to conclusions as just because a Garmin "might" do this doesn't mean any other or all other manufacturers implement things the same. As usual one generally has to keep an open mind on many of these things as sometimes many things disguise the real facts.

Cheers, Kerry.

There is a way to test this with several receiver types at one time. A volunteer is needed who lives near an amusement park with any type of roller coaster with big drops--Sandusky, anyone?

Anyway, it should be easy enough to find out the total track length for a coaster, which would include all loops and rises/drops. Check the odometer when finished and compare to the out-and-back distance if you were to walk to the farthest point and back on the ground.

Modify this setup as required.

don

A volunteer is needed who lives near an amusement park with any type of roller coaster with big drops--Sandusky, anyone?
I'll go out on a limb here and suppose that this "Product Support Specialist" is either sadly misinformed, or makes up answers when he doesn't know the right one.

He doesn't even know how to spell horizonitcaly...

Driving 1.000 (choose your unit) at a 10% decline is actually only 1.005 (choose the same unit) long. Declines as "steep" as 10% usually reward warning signs along the roads. Still, the difference in distance is below the (usual) inaccuracy of the receiver.

Only in very steep terrain does the distance make any significant difference. Notice that the GPS do take into account the (usually) windling route trails and roads in such hilly terrain takes.

My own experience with a Vista says that it does not take the vertical component into account. At Garmin, they (some?) seem to be of another opinion. Perhaps it doesn't make any difference there. Just how horizontical is Kansas City?

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