Calculations of atmospheric and molecular absorption spectra of gases using the HITRAN database. The user specifies the concentrations of molecules, total pressure, temperature, optical pathlength and other parameters which are used to model the gas mixture optical transmission spectra as a function of wavelength. Automatic HITRAN database downloads (from or manual placement of the database onto the portable device. Optional usage of SensorTag and Cell phone sensors for empirical readings of total pressure, temperature and H2O vapor concentration through humidity measurement (humidity measurement is currently only available using SensorTag) to provide input for line-by-line calculations instead of manual entry and generate absorption spectra based on measured ambient conditions. Remote bytran execution over WiFI / Ethernet, Bluetooth or Serial port using the bytran communication protocol. Built in atmospheric models. Voigt, Lorentzian and Doppler lineshapes. Instrument functions. Sharing calculation results (images and data) from within the application. Absorption, Transmission or Optical Depth spectra. Currently limited to horizontal path mode. Additional information is available in the following publication, (a view only version of this publication is available at

What's New

Version 1.3

1) Capability to control bytran remotely (over WiFi / Ethernet, Bluetooth, and the Serial Port) using the bytran communication protocol.
2) Spectrum pan feature and the spectrum coordinate rulers on zoom.
3) Calculated data made available as absorption cross-section
4) Radiance calculations for individual molecules
5) Added cosine instrument function (from HAPI)

For a complete list of changes and bug fixes please refer to:


Dzianis Pliutau
44.4 MB
Requires iOS 8.0 or later. Compatible with iPhone, iPad, and iPod touch.
Age Rating
Rated 4+
© 2016 Dzianis Pliutau


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.