Altimeter help

For the iPhone and Android apps and the web app at altitude.hertzmc.com

How accurate is it?

It's a good guide, not survey or aviation equipment. GPS elevation is usually within about 10 to 50 feet (3 to 15 m) outdoors with a clear sky, and less exact under trees, between tall buildings, indoors or in the first minute. The ± number under the reading is your phone's own estimate. Don't use Altimeter for flying, climbing safety or anything where a wrong height could hurt someone.

GPS and the barometer

GPS gives your height above sea level, but it jumps around a little.
Barometer (most phones, in the apps): air pressure drops as you go up, so the apps use it for smooth, precise changes. Weather also changes air pressure, so the apps keep the barometer lined up with GPS in the background.
The status at the top says what's in use: "GPS", "GPS + barometer", or "Barometer" when GPS is gone (indoors).
The web app can only use GPS: browsers can't read the air pressure sensor.

Set elevation

If you know the exact height where you are (a trail sign, a summit marker, a map), tap Set elevation in the app, type it in and tap Save. The barometer then measures from that height, like a real altimeter. Weather slowly moves air pressure, so set it again after a few hours, or tap Use GPS again. It needs a phone with a barometer.

Climb and descent

Climb adds up every bit you went up, Descent every bit you came down, since you last tapped Reset trip.
Small ups and downs are left out so jitter doesn't add up: under about 7 feet (2 m) with the barometer, under about 30 feet (10 m) with GPS only.
They count while Altimeter is open. If you lock the phone or switch apps, the difference between where you left and where you came back still counts, but not the ups and downs in between. Altimeter doesn't track you in the background.
Lowest and Highest are the lowest and highest elevation on this trip; the profile shows the whole trip.

It says "Location is off"

iPhone: Settings → Altimeter → Location → While Using the App, and turn on Precise Location.
Android: Settings → Apps → Altimeter → Permissions → Location → Allow only while using the app, and turn on Use precise location.
Web: allow location for altitude.hertzmc.com in your browser's site settings.

No elevation on a computer

Most computers find their location from Wi-Fi, which has no height. Open altitude.hertzmc.com on a phone with GPS instead.

The apps are free and show one small banner at the bottom. See the privacy policy for what the ad collects. Altimeter never sends your GPS location anywhere.

Contact

Email altimeter@hertzmc.com.