Suggestions for an altimeter?

While you are looking, take solace in google maps

 

Hubby uses a Casio watch which has a compass and altimeter in it. About $120.
It only updates every few minutes though.

 

Get one on ebay out of an old airplane

 

solace |ˈsälis| noun comfort or consolation in a time of distress or sadness : she sought solace in her religion. verb [ trans. ] give solace to. ORIGIN Middle English : from Old French solas (noun), solacier (verb), based on Latin solari ‘to console.’

 

If you want to know how level the road is... it sounds like you would rather have a vertical speed indicator (VSI) rather than an altimeter... although the VSI function could be estimated by watching how fast the altimeter moves.

I wish that the GPS had an altimeter readout as well. It would be nice to know how much more climbing was ahead until the mountain pass. I would not install a seperate instrument to get this however. It would be nice to have it on my watch.

/Jim

 

To get an accurate reading of your altitude, you need an altimeter with an adjustable barometric setting. In Aviation this is done with what we call "Kollsman" knob and you read the setting (in inches, mercury) in the Kollsman window. Without such a setting, your altitude reading will change from day to day, in the same geographic place, according to the ambient atmospheric pressure.

I got a small altimeter with a rotating cover that allows me to set the default barometric pressure. The problem is that the face is only about 2.5 inches in diameter, and the pressure scale is divided into increments too wide to be of any use.
Put in other words: For every 1000 feet of altitude, the pressure drops (going up) one inch of mercury; the difference in altitude between a reading of 29.90 inches of mercury, and 30.00 inches of mercury is 0.1 inches, or 100 feet. Altimeters sold for use in cars are too small to have a meaningful or readable scale on them, and, as you can see, it doesn't take much of a change in barometric pressure to affect big changes in actual altitude.

The accuracy of my little car altimeter is about plus/minus 500 feet at best; not very accurate for what you are looking for. To get a correct reading from a pressure altimeter (as opposed to a GPS), you need a source of local barometric pressure. We get that in the airplane from air traffic control, but you can't access that info in a car.

My Garmin 295GPS unit, however, is much more accurate once I set the altitude (not the barometric pressure). By going to a location, i.e. Boeing Field in Seattle where I teach, where the altitude above sea level is known, I can set the GPS and have it read pretty accurately elsewhere in the city. As long as the GPS can get a signal from enough satellites to do 3D computation, it will give me a reasonable altitude reading, although NOT accurate enough to be used as a primary flight data source unless the GPS is certified for use in instrument conditons.

Way more of an answer than you expected; hope this helps somewhat. I guess the bottom line is that GPS is better than a mechanical altimeter unless you want to pay huge bucks to adapt some aviation altimeter to your car.

Bob

 

GPS units measure altitude in one of two different ways: by a direct satellite reading, or by barometric pressure. Neither one is suitable for your intended use of determining if a road is level.

The direct satellite reading method does not require any settings, but is extremely inaccurate, because all the satellites are overhead. My hand-held eXplorist told me my altitude had varied by 100 feet as I walked my extremely level jogging route in flat Fargo. The barometric pressure method is probably more reliable, if you have a starting point of known altitude to set it by, or a source for the current pressure. But as noted above, it is extremely imprecise. (Note that precision and accuracy are two very different things.) More expensive GPS units typically use barometric pressure for altitude, while cheaper ones like mine use direct satellite reading.

What you really need is a surveyor's transit, so you can survey the road in question. Or use the topographic map bundled in the software for some GPS units, which contains altitude data.

 

My little Garmin unit is pretty squirrely when trying to display
altitude, probably for the reasons given, and can vary up and down
by several tens of feet just sitting still. But it was accurate
enough to tell me the ballpark height of the mountains I was going
over back in December.
.
Toyota is reputedly working on a GPS-based efficiency helper which
would take terrain into account when managing the engine, battery,
cruise-control, etc. Presumably that would be done via topo
information mapped to lat/long in the internal database of the GPS,
as opposed to altitude measurement, especially because it's got to
be predictive. Cool idea; not sure how much real-life gain can
be had. Probably depends on how well the driver reads the upcoming
terrain and tailors right-foot response in the first place...
.
_H*

 

The aviation recommendation is good. You can get the local altimeter settings by purchasing a receiver or scanner that receives air frequencies and monitoring ATIS.

 

I presume you're looking for a pressure altimeter. Don't know of any available for measuring minor changes in terrain.

Personally I use a cheap Magellin which seems to work well for what you're describing. Sometimes while on a long drive I'll monitor both the gps and the mpg just for fun and find a definite direct relationship (slow nearly imperceptable rises yield lowered mpg - and vise versa.

 

The hiking/climbing community uses wristwatch altimeters. They are plenty accurate for most purposes. Check rei.com or many of the other hiking oriented webpages for examples (Casio, Avocet, many other brands). Most of them have battery-saving options that limit how often the display updates. SOme have fancy gizmos like total elevation gained, dropped (for skiers), etc.

Of course, you have to set it at a known elevation, due to weather changes.

If you are always in open terrain (i.e., no trees blocking the view of the satellites, no tall buildings, no cliffs, etc.) than a handheld hiking-oriented GPS can be very accurate. If the terrain is more challenging, you need a GPS that has a quad helix antenna (Magellan Sportrak, for example) instead of patch antenna (Garmin eTrex, for example).

I've been on many peaks and saddles that are triangulated elevation points, and been well within 50' elevation on the GPS and altimeter watch. Most topographic maps are only accurate to 40' anyway (topozone.com for instance).

Us peak-bagging fanatics live and breathe by altimeters. Very important tool! I just recently went with the GPS and it's a fun toy too.

So whatcha gonna use an altimeter for?

 

Boy, o boy, am I ever skeptical of this!!! I checked out REI, and it says the readout on its $170 watch is in 3-foot increments. Do you know the difference between precision and accuracy? BIG difference: Lots of measurement equipment has extremely high precision but much lower accuracy. The watch might give you a read-out in 3-foot increments and yet only be accurate to plus or minus 20 feet, and even that would surprise me.

My Magellan hand-held GPS displays altitude in very small increments, but appears to be accurate only to within a hundred feet or so.

 

"My Magellan hand-held GPS displays altitude in very small increments, but appears to be accurate only to within a hundred feet or so."

Actually, 100ft is unusually excellent for a GPS-only altitude reading; it will usually be far less accurate because of poor sat geometry.

 

Sounds like a cool watch.

I used my Magellen plugged into my car's power outlet to look at "change" in elevation as I drove (compass too being navigationally challenged). It worked very well for that. Absolute elevation not that important from my perspective.

 

But precision is desired here I'd imagine, rather than accuracy. That is to say, the change in elevation is of interest.

 

Windstrings,
Sounds like what you want is an Inclinometer. We used 'em on Submarines. Tiltmeter

The electronic versions even have accelerometer function built in, but they are probably around 4 to $500.00. Acumar


Check this out on E-bay: Toyota Inclinometer/Altimiter

Now if I could just find a periscope, I wouldn't need that backup camera. :lol: