Jepp question
 

KILM
Approach info:
ILS 6 Apt Elev 32' Rwy 6 21'
ILS24 Apt Elev 32' TDZE 26'

Two precision approaches to the same runway. Why does 24 have TDZ elevation and 6 have Rwy elevation?

My guess is because the TDZE on 6 is the same elevation as the end of the runway.

On 24, the end of the runway is 20', where as the TDZE is 26'. (TDZE is the highest elevation in the first 3000' of the landing surface.)

It's likely that the FAA/Jepp will chart the highest elevation for either Runway End, Threshold Elevation, or TDZE.

I think you're right. If you look at the airport diagram, the Rwy 6 elevation from the chart matches with the Elev arrow at the end of the runway. Awesome! Thanks for your help.

jake -

I know that Jepp grabs their information from the FAA databases and there is a switch going on in the charting conventions.
The minimums were calculated from the TDZE (as you see from the ILS RWY 24 approach plate - at least from the TPPs). This approach was commissioned back in early 2007 and is still an ORIG-A version.

ILS RWY 6 was also commissioned in early 2007, but has undergone an Amdendment update as early as May 2011. It is using the new convention of a reference point on the threshold (THRE) for calculations of the minimums.

I think this has something to do with the differences that you are mentioning. It is my understanding that has approaches are updated you will see the measurement point changing.

USMCFLYR

That makes sense as well. *grumble grumble aviation grumble nothing's ever simple grumble grumble*