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PlanarRad is free software for modelling light in natural waters or other homegenous scattering and absorbing media. It is functionally similar to the commercial software Hydrolight.

PlanarRad does not have:

  • Infinite depth water
  • Vertical stratification of optical parameters
  • Inelastic scattering (chlorophyll or CDOM fluoresence, Raman scattering)
  • Any bio-optical models, you must provide IOPs directly rather than chlorophyll concentration. However PlanarRadBatch provides functions for this.

However PlanarRad does have:

  • An attractive price point - it's free as in beer
  • Open source code licensed under the GPL - it's free as in freedom
  • Highly scriptable command-line interface
  • Output results in an easily manageable text file
  • GUI front-end with interactive visualisations and plots (ideal for educational use)
  • Automatic spectral resampling for easy integration of data from multiple instruments
  • Ability to load in actual irradiance or radiance profiles for comparison to model outputs - i.e. model closure experiments
  • Easy reconfiguration of the directional discretization of radiance - no recompiling required
  • Nearly identical results to Hydrolight that can be verified on your own machine - example report
  • A user-generated user manual. You are reading it! Please contribute!

More Information

PlanarRad is a freely available open-source C++ implementation of the invariant imbedded numerical integration technique for calculating radiative transfer in plane-parallel media with an opaque bottom boundary. It is based on the algorithm described in Curt Mobley's book Light and Water, and was designed for modelling light propagation in, and reflection from, shallow water environments. However, by setting a suitably large depth an infinite depth solution can be approximated. PlanarRad was developed by John Hedley (me) during a period in which I was based at the University of Exeter and variously funded by Natural Environment Research Council and the World Bank / GEF Coral Reef Targeted Research Project. The NERC Field Spectroscopy Facility also indirectly supported PlanarRad by funding the development of the WLTool software.

The PlanarRad program for Windows and Linux (including source code) can be downloaded here:

Linux source code: planarrad_free_src_0.9.5beta_2015_07_17.tar.gz

Windows version:

Information on installation and testing is below.

Citing PlanarRad

If you make use of PlanarRad in a publication the most suitable peer-review publication to cite is:

Hedley, J (2008). A three-dimensional radiative transfer model for shallow water environments, Optics Express 16, 21887-21902.

The main topic of that paper is a different radiative transfer model, but PlanarRad was also used and Figure 5 of that paper can be considered a validation of PlanarRad by model intercomparison.

See here for the Full list of publications using PlanarRad.

If you publish anything using PlanarRad, please let me know via the email address below so I can update the list of publications.

Installation and Usage

Installation from source on Linux

Windows installation

Building the Hydrolight comparison document

Getting started with PlanarRad

General scattering and absorbing media

Command line running (Linux)

Other downloads

Versions from the Light & Photosynthesis on Coral Reefs course at UNAM

Previous versions

Contibute to this Wiki

This wiki is intended to be user-generated, so all contributions are very welcome. No need to worry about the quality of presentation or even the accuracy, just get the information up here! Due to spamming to get an account you have to email: john<at>

Support and bug reports

PlanarRad is unfunded so my ability to provide support is extremely limited. Nevertheless I am likely to respond to an email, and can be reached by john<at> If you would like to help PlanarRad survive, bear in mind that with financial support I can provide custom modifications, training, support services or use PlanarRad to provide results for your project. This will likely be very cost effective compared to purchasing other commercial software options, and will help me maintain the software for the benefit of all. So get in touch!