[tlhIngan Hol] qelI'qam

[seruq]

I've known a qelI'qam only to be roughly 2km.
There are numerous corporate websites out there with hidden tlhIngan Hol web pages, and the ones that make reference to qelI'qam are using a calculation of 1 qelI'qam = about 1.6 km.
If these pages were all written by the same person/team, that would explain the consistent use of the 1.6, but... where are they getting that 1.6 from?  Do we have additional canon implying this?