# Best portable device for measuring elevation?
**URL:** https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586
**Category:** Factual Questions
**Created:** [December 18, 2010, 2:22am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586 "2010-12-18T02:22:17Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Mangosteen](https://boards.straightdope.com/u/Mangosteen)
#### Post date: [December 18, 2010, 2:22am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/1 "2010-12-18T02:22:17Z")
Is there a reasonably priced hand held device that will measure ones elevation above sea level?
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### Author:  [@not\_alice](https://boards.straightdope.com/u/not_alice)
#### Post date: [December 18, 2010, 2:33am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/2 "2010-12-18T02:33:32Z")
A GPS with an altimeter? Or just an altimeter? I used to have a parasailing friend who had one IIRC.
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### Author:  [@Mangosteen](https://boards.straightdope.com/u/Mangosteen)
#### Post date: [December 18, 2010, 3:00am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/3 "2010-12-18T03:00:57Z")
I just want to find the high point on a seven acre property that I am looking at.
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### Author:  [@Reply](https://boards.straightdope.com/u/Reply)
#### Post date: [December 18, 2010, 3:09am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/4 "2010-12-18T03:09:24Z")
If you have a friend with a smartphone (iPhone or Android), you can probably get them to get a GPS altimeter app and just walk up the hill with you.
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### Author:  [@Reply](https://boards.straightdope.com/u/Reply)
#### Post date: [December 18, 2010, 3:11am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/5 "2010-12-18T03:11:33Z")
Otherwise, maybe something like [this](http://www.amazon.com/GSI-Quality-Outdoor-Exercise-Handheld/dp/B00478K3AS/ref=sr_1_18?ie=UTF8&qid=1292641658&sr=8-18) ($30)?
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### Author:  [@Reply](https://boards.straightdope.com/u/Reply)
#### Post date: [December 18, 2010, 3:12am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/6 "2010-12-18T03:12:33Z")
Oh, you also might be able to just find the hill on a topo map (Google Earth or USGS or your local outdoor store), though I’m not sure if that’ll give you the precision you need.
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### Author:  [@Xema](https://boards.straightdope.com/u/Xema)
#### Post date: [December 18, 2010, 3:12am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/7 "2010-12-18T03:12:42Z")
> [@Mangosteen](#):
>
> I just want to find the high point on a seven acre property
Google Earth is quite useful for that sort of thing.
If you want an instrument that will do this, a [Kestrel](http://www.nkhome.com/kestrel/kestrel-4000/) would be a good way to go. You need to understand how barometric altitude measurements work (for good accuracy, you need to start at a known altitude, or get a local pressure reference).
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### Author:  [@China\_Guy](https://boards.straightdope.com/u/China_Guy)
#### Post date: [December 18, 2010, 3:17am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/8 "2010-12-18T03:17:05Z")
There are altimeter watches out there. IIRC, one for about $80 on amazon. Works pretty well as long as the tempeture is constant. You can calibrate it as well. Might do the trick for you
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### Author:  [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)
#### Post date: [December 18, 2010, 3:22am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/9 "2010-12-18T03:22:42Z")
> [@Reply](#):
>
> Oh, you also might be able to just find the hill on a topo map (Google Earth or USGS or your local outdoor store), though I’m not sure if that’ll give you the precision you need.
This is the best way to do it. Non-professional GPS units and cheap barometric altimeters both have less vertical accuracy than a typical 20 ft. contour topo map. Just use your favorite method to orient yourself horizontally and see what either the USGS topo map or the google earth DEM says your elevation is. If you need more precision than that, you need a professional.
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### Author:  [@TriPolar](https://boards.straightdope.com/u/TriPolar)
#### Post date: [December 18, 2010, 3:25am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/10 "2010-12-18T03:25:55Z")
A barometer
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### Author:  [@Mangosteen](https://boards.straightdope.com/u/Mangosteen)
#### Post date: [December 18, 2010, 3:46am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/11 "2010-12-18T03:46:09Z")
I’m not sure if an altimeter will tell me what I want to know.
I’d like to find out how far above sea level I am, not how high off the ground I am.
There aren’t really any hills around that are significant enough to show up on a topo map.
The ocean is only half a mile away. I guess I could go there with some kind of instrument, establish “sea level” and walk uphill to the property from there.
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### Author:  [@Reply](https://boards.straightdope.com/u/Reply)
#### Post date: [December 18, 2010, 3:47am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/12 "2010-12-18T03:47:47Z")
Why would a non-professional GPS be less accurate? (I’m not being snarky; I’m just not sure how they work and what the difference between the expensive ones and the normal ones are.)
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### Author:  [@Balthisar](https://boards.straightdope.com/u/Balthisar)
#### Post date: [December 18, 2010, 3:52am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/13 "2010-12-18T03:52:34Z")
> [@Mangosteen](#):
>
> I’m not sure if an altimeter will tell me what I want to know.
>
> I’d like to find out how far above sea level I am, not how high off the ground I am.
Uh, that’s how [altimeters](http://en.wikipedia.org/wiki/Altimeter) work. Everything has an altitude above MSL, even if you’re on the ground. I’m sure you’ll give yourself a good :smack: when you think about it just a couple of seconds.
> [@](#):
>
> There aren’t really any hills around that are significant enough to show up on a topo map.
You’re going to give yourself the same :smack: when you think about this, too. Topo maps have all elevations marked. You don’t need a peak. You just need to know where your property is on the map.
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### Author:  [@enipla](https://boards.straightdope.com/u/enipla)
#### Post date: [December 18, 2010, 4:53am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/14 "2010-12-18T04:53:24Z")
Download GoogleEarth. It’s free.
USGS maps are cheep. And mostly free online
Or use a hiking GPS like a good Garmin.
Or, if the property has an address, I bet I could find it if you let me know what State and county it is in. All free. Just figure out the lat and long and use GoogleEarth. It should be within about 20 feet.
What’s the address and State and County?
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### Author:  [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)
#### Post date: [December 18, 2010, 6:04am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/15 "2010-12-18T06:04:38Z")
Speaking of sea level, is there a particular reference point somewhere on Earth that is defined as 0 feet? The tides are always pulling the water up and down, and IIRC there are even height differences among the oceans that cause all kinds of turbulence, freak waves and the like, around the southern tips of Africa and South America. So how is the standard set?
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### Author:  [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)
#### Post date: [December 18, 2010, 6:38am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/16 "2010-12-18T06:38:29Z")
> [@Boyo\_Jim](#):
>
> Speaking of sea level, is there a particular reference point somewhere on Earth that is defined as 0 feet? The tides are always pulling the water up and down, and IIRC there are even height differences among the oceans that cause all kinds of turbulence, freak waves and the like, around the southern tips of Africa and South America. So how is the standard set?
The measurement is taken from above mean sea level (AMSL) which would just be the local mean.
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### Author:  [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)
#### Post date: [December 18, 2010, 6:58am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/17 "2010-12-18T06:58:26Z")
What is the local mean of sea level in Wisconsin? I haven’t noticed any nearby seas. Lake Michigan? Lake Mendota (the largest local lake)?
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### Author:  [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)
#### Post date: [December 18, 2010, 10:12am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/18 "2010-12-18T10:12:58Z")
It looks like I was wrong about using a local mean and that they use the [geoid](http://en.wikipedia.org/wiki/Geoid) which is a theoretical datum.
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### Author:  [@ticker](https://boards.straightdope.com/u/ticker)
#### Post date: [December 18, 2010, 11:45am UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/19 "2010-12-18T11:45:21Z")
GPS altitude levels may be inaccurate because a) the orientation of satellites makes such measurements inherently less reliable and b) the shape of the Earth assumed by GPS (WGS84) is often quite different from the geoid at that location. Cartographic organizations such as the UK’s Ordnance Survey publish tables of corrections from WGS84 to local datums.
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### Author:  [@Kevbo](https://boards.straightdope.com/u/Kevbo)
#### Post date: [December 18, 2010, 1:58pm UTC](https://boards.straightdope.com/t/best-portable-device-for-measuring-elevation/564586/20 "2010-12-18T13:58:23Z")
An aircraft mechanical altimeter (AKA aneroid altimeter, AKA Kollsman altimeter) will have 20’ resolution, but will need tapping to overcome interal stiction. You can estimate between the divisions to perhaps 5’.
A very sensitive electronic altimeter will have 1 foot resolution. I built one for hang gliding use back in the late 80s. Noise and drift of the pressure transducer limited the resolution, and they have not gotten much better. (These were among the first MEMS devices) This was as good as we got with the Sperry vibrating diaphram transducers used in aircraft air data systems (I was working for Sperry/Burroghs/Unisys/Honywell at the time)
Which is probably not good enough if the area is rather flat. Consider two measurements, each having +/- 1 foot of error. The range of uncertainty in the difference is 4 feet in total.
The “right” way to do this is with a surveyer’s transit level, or a laser level. This is where the data used to draw the topo maps comes from. You might be able to rent such at a tool rental place.
If the property is not large, a water level might be useful. You can compare the height of two places separated by as much garden hose as you have to well under an inch. These are cheap, have virtually no sources of possible error, and I would trust this more than any under $1000 laser level.
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