Scientific Altimeter

Precise Elevation Measurement for Research and Field Work

About

Scientific Altimeter is a professional-grade elevation measurement tool designed for researchers, scientists, and outdoor professionals. The app combines GPS altitude data with barometric pressure readings and ground-truth calibration using USGS elevation data.

Key Features

How It Works

The app uses your device's GPS and barometer sensors to measure altitude. For improved accuracy, it can calibrate the barometer using USGS ground elevation data from the National Map Elevation Point Query Service (EPQS).

Data Source: USGS EPQS API (epqs.nationalmap.gov) - A free, public government service providing ground elevation data.

Requirements

• iOS device with GPS capability
• Location permission (required for GPS altitude)
• Internet connection (for USGS calibration only; not required for basic operation)
• Works best outdoors with clear GPS signal

Privacy

This app collects location data solely for altitude measurement and USGS calibration. No location data is stored, shared, or transmitted to third parties. Location queries to the USGS API contain only latitude/longitude coordinates needed for elevation lookup.

Frequently Asked Questions

Why does the app need location permission?

Location permission is required to access your device's GPS for altitude measurement and to query the USGS API for ground elevation calibration.

Does the app work offline?

Yes. The app can operate in GPS-only mode without internet. Barometer calibration requires internet to access USGS data, but manual calibration can be used offline.

How accurate is the altitude measurement?

GPS altitude typically has accuracy of ±10-20 meters. When calibrated with the barometer, accuracy can improve to ±1-3 meters depending on atmospheric conditions.

What is the USGS API?

The USGS Elevation Point Query Service is a free, public API provided by the U.S. Geological Survey that returns ground elevation for any location in the United States.