The irradiance map viewer can be used to view, merge and save irradiance map files created by V-Ray.
By default, the installation of V-Ray for Maya installs the irradiance map viewer in the folder [Program Files]\Chaos Group\V-Ray\Maya for nnnn\tools. A shortcut to the irradiance map viewer can be found within Start Menu > Programs > Chaos Group > V-Ray for Maya > Tools > Irradiance map viewer.
Windows: start the imapviewer executable from C:\Program Files\Chaos Group\V-Ray\Maya nnnn for x64\bin\
Linux: start the imapviewer executable from /usr/ChaosGroup/V-Ray/Mayannnn-x64/bin/
Mac OS X: start the imapviewer executable from /Applications/ChaosGroup/V-Ray/Mayannnn/
Note: nnnn is the Maya version.