There is only one file type that uses the .LTL extension:
Luminaire Data File
Data file used by DIALux, a program that enables you to model and plan lighting for indoor and outdoor environments; contains data about a light fixture's power consumption, luminous flux, light intensity, light radius, and more; referenced by DIALux to model the light fixture's capabilities.
To open a LTL file in DIALux, select, navigate to your file, and click .
NOTE: Similar to other Luminaire data files such as .LDT, .ELD, .CIB, and .IES files.
Updated: October 22, 2013