Pick an Altimeter — The Mountaineers (2024)

Early altimeters with 19 jewels and Swiss-made movements were price-prohibitiveand thus weren’t included in either The Mountaineers navigation courses or the TenEssentials. However, with new technology emerging, the upcoming 9th edition ofFreedom of the Hillswillfeature map, compass, and all of the modern tools with altimeters prominentamong them.

Since mountains are not two-dimensional...the altimeter is sometimes as helpful as the compass, particularly where topographic maps are available. With altitude known,point-position can often be found with only one visible feature recognized;in any other case, altitude provides a check against map and compassorientation. -Mountaineering: The Freedom of the Hills, 1st ed. 1960, p. 79

In October, some 70 navigation students took the newly namedWilderness Navigation class (FKA Basic Navigation). The class has been updatedby the Seattle Navigation Committee with input from several branches, and guidedby the results of the June 2015 Navigation Summit. The course now prominentlyfeatures the altimeter and lays a solid foundation for GPS use.

How cheap can you go?

Now that Swiss jewelers are no longer needed to make an altimeter, just howcheap can we go? It’s easy to spend $130 to $350 on a Suunto Core ABC(altimeter, barometer & compass) watch. But how functional is a ~$30 Casiomulti-function watch? Or cheaper still, how functional are the many, free cell phoneapps?

It was a little awkward to wear three wrist altimetersand more awkward still to ask my spouse and climbingpartner to wait in a snowstorm on the Muir snowfieldwhile I recorded data. But the results are in and theyare clear. The cheapos work great. I can highlyrecommend at least one cheap watch and a handful ofmostly Android cell phone apps.

The Test

Itested three wrist altimeters and six apps on my Samsung Galaxy S5 smartphone. The S5 has a built-in altimeter chip as do the latest iPhone 6 models. The apps were picked were freeand strongly rated.

For wrist altimeters I used my 15+ year old Suunto Observer, a new Suunto Core, and the cheapest altimeter I could find on Amazon—the “Casio SGW300H-1AVCF Twin Sensor Multi-Function Digital Sport Watch.”

In addition to the six apps from the Android Play Store (https://play.google.com), I performed a cursory test of three iOS apps (http://itunes.apple.com) with similar results. See Table 1 for tool details. In the end, tool choice made no material difference.

These tools use three, quite different methods to determine altitude. Thetraditional method measures atmospheric pressure, as do barometers, butcalibrated in feet rather than inches of mercury (or meters vs. millibars). Sinceweather effects air pressure, and therefore apparent altitude, these tools must becalibrated at the start of a trip and perhaps during. I calibrated them at thetrailhead to a known elevation and made no further adjustments.

Tools that determine altitude using GPS use two quite different methods. The firstGPS altitude method takes the absolute position in 3D space and compares it to amath model (the ellipsoid) that approximates mean sea level. GPS technology hastaught us that the sea isn’t as level as we thought and undulates considerablyaround the world. Using a built-in table, modern GPS units then correct for thedifference between the ellipsoid and local mean sea level. Early GPS units did notmake this adjustment. Perhaps this is one reason GPS units have an undeservedbad reputation for determining elevation.

The other way GPS determines altitude is to assume that you are standing on thesurface of the earth (a bad assumption for pilots in flight). The tool then uses GPScoordinates to find elevations in a lookup table. An Internet connection is requiredso this is not practical for wilderness navigation. If the Internet is not available,these apps default to the 3D method.

TABLE 1 - ALTIMETER TOOLS TESTED

Altimeter Apps Tested

Methods

The test was simple. I took all eight tools on four trips: three at in Mt. Rainier NP(a glacier climb to Whitman Crest below Little Tahoma, a climb to Anvil Rock nearCamp Muir and a hike to Mildred Point) and one hike to the summit of San JacintoPeak near Palm Springs, CA. I took measurements along the way and thencompared with a gold standard “actual” elevation based on GPS location.

While we might like to know elevation with great precision, mountain navigation istolerant of several hundred feet of deviation. The bold topographic index lines on a1:24000 (7.5 minute) USGS map are 200 vertical feet apart so I set two criteriafor success:

1. Each individual altitude measurement does not deviate more than 300 feetfrom actual. As long as all measurements are within 300 feet (150% of thedistance between bold lines) of actual, you will not be more than one bold line off from the actual nearest bold line. This is not a potential 600-foot error.
2. The average altitude measurement is within 100 feet. Ideally, the altimeterswould, on average, put you on the correct bold map line.

I assumed that some of the apps or the $30 Casio special would produce materialerrors, especially over large changes in altitude.

Ain't Misbehavin'

For these three trips, I could not get any of the wrist altimeters or apps tomisbehave, with two exceptions that I’ll address below. Each device’s worstindividual reading was within my criterion of success of +/-300 ft. with the worstindividual reading varying by 259 ft. On average, the tools were almostridiculously accurate with the worst average difference being only 60 ft. This wassurprising especially considering one of the trips was over two days with anelevation difference of 5400 feet.

While all the tools performed exceptionally, the GPS apps were more accurate. Ifthe barometric altimeters had been recalibrated, as recommended for a normaltrip, they would have been even more competitive.

Using GPS for elevation data tends to raise eyebrows but the data says thisreputation is undeserved. The data allowed me to test this question in addition tothe main topic of this paper. I compared Gaia GPS, my go-to favorite navigational
tool with actual elevation data. I was able to take 14 measurements in diverselocations from the San Jacinto Mountains of southern California to Calgary,Canada. Table 2 compares the Gaia GPS measurements against good map data.

Table 2: Gaia measures compared to topo map elevations

A few cautions are in order. There were two anomalies that surfaced duringtesting, both with wrist altimeters. On the summit of San Jacinto Peak it wasbelow freezing. When I took the watch off my wrist to use the built-inthermometer, the temperature plummeted until it hit 35F and then shot up to over200F. The altitude, which had shown a reasonable 10,800 ft., shot up to 27,400 ft.If anyone can explain this, please let me know. When the altimeter was back onmy wrist, readings returned to normal.

The second anomaly was with the Suunto Core. This watch has large buttons thatprotrude. There is a locking mechanism that I had not engaged and on one trip,the buttons were accidentally pushed and the watch adjusted to the wrong altitude.I left this data out of the results.

Also, remember smartphones are fragile, power-dependent electronics so geta credible case, turn it off (or to airplane mode) between uses and have a map,compass and backup tools. Wristwatch altimeters and apps that rely onatmospheric pressure are subject to changes in weather. Keep that in mind andrecalibrate when the altitude is known (map position) or recalibrate against GPSwhich is unaffected by weather. There were no dramatic changes in weather and Idid no recalibration during the tests.

Table 3. Field test results dedicated altimeters and Android apps

Table 3 Note: Average and maximum deviation is the difference between the tooland the actual known elevation as determined by the Google elevation service.Where the tool uses both atmospheric pressure and GPS, each is shown with theatmospheric first followed by GPS to the right of the slash.

Take this study as a strong recommendation to add an altimeter (or two!) to yournavigation tools. A cheap Casio wristwatch altimeter will run for years on onebattery and if you have a smart phone, add a free app. Or, better yet, add GaiaGPS for $20 and have a world-class navigation tool in your pocket.

Steve McClure sits on the Mountaineers Board of Directors as Treasurer, chairsthe Finance Committee, and sits on the Seattle Climbing, Scrambling, andNavigation committees. He is an intermediate climbing student. Contact him atMcNorth@Gmail.com.

Editor's Note: The Seattle Navigation Committee invites prospective gear reviewersto submit requests to test new navigation tools. The Committee will reimburse thereviewer for the tool and offer it to the reviewer to keep at a 50% discount.Submit your brief (1 page) review proposal to the editor. Specify your experience,committee(s) affiliation, tool, source, cost and review procedures in your proposal.