POSSUM

## Adding white (thermal) noise

POSSUM GUI adds any noise you have specified before running POSSUM. However, if you want to add different levels of noise to the same simulation you should do that by using two easy and quick command-line programs.

Firstly, you should add thermal noise to your signal (or signal_nonoise if the signal is already generated with added thermal noise) by the use of a command-line program systemnoise. If you type systemnoise into your terminal you will get something similar to this:

    systemnoise

    systemnoise [options] --in=signal_nonoise --out=signal_with_noise --sigma=value

    Compulsory arguments (You MUST set one or more of):
            -i,--in         input signal
            -o,--out        output signal

    Optional arguments (You may optionally specify one or more of):
            -s,--sigma      set noise standard deviation (units of intensity)
            --seed          input seed value for the sequence
            -v,--verbose    switch on diagnostic messages
            -h,--help       display this message

Note that the output of this command-line should not be given the same name as the input because in that case you will lose your original signal file (which usually takes a long time to generate).

After you have added thermal noise to the signal, you can reconstruct the image using a command line program signal2image.

Copyright © 2007, University of Oxford. Ivana Drobnjak and Mark Jenkinson.