In this case it would place the aircraft at an altitude of 645 ft (300 AGL) at the middle marker which appears about right.
jfill, you are not quite right here. Let me put in my five cents as retired military ATCO and PANSOPS procedure designer (+MEPL IFR).
The whole procedure looks to me that it was constructed pre-PANSOPS with the VOR/DME as FAF at 3.8 NM from TD and the MAPt most probably at the threshold for RWY 15. Note the obstacle situation in the departure sector (terrain 3006 ft MSL). The charming aspect is that you could have flown the procedure even with DME inop or the aircraft not equipped accordingly by using a time table to determine when passing the MAPt
With the introduction of PANSOPS and its excessive requirements (just ask any PANSOPS guy to fit a CAT C holding at 5000 ft MSL to an NDB surrounded by a 10 x 15 NM controlled airspace) there was apparently no chance to keep the MAPt at passing threshold at 400 ft AGL. Using the required climb gradients for the missed approach they had to relocate it starting 1.9 NM outward from the THR RWY15 and change the FAF to DME 2.3 to allow for the required max descent gradient. The designer had to find a compromise between the required minimum visibility and minimum ceiling for the approach. Putting the MAPt closer to the TD would have resulted in a higher MDA, and putting it further out would have resulted in higher visibility requirement.
It is safe to assume that the pre-PANSOPS minima for Pakse were a lot lower, but PANSOPS insists on creating procedures based on the "worst case" scenario - sloppy flying, inaccurate on-board instruments, shoddy nav aids and hideous wind speeds (omnidirectional) not compensated by the pilot.
Your interpretation of the required altitudes based on this misleading table shows the inherent danger of sloppy charts. Breaking out of clouds at 300 ft AGL on a 500 ft/min descent rate in a non-precision approach and still being almost 2 NM from the RWY at the "middle marker" (actually it is the MAPt based on DME as there are no marker beacons for this type of approach) does not meet any safety standards.
The correct straight-in minima are:
- Ground Visibility 3200 meters
- MDA (MSL) Cat. A-C: 949 ft MSL
- HAT (AGL) Cat. A-C: 645 ft AGL
- Ceiling: Cat. A-C: 700 ft AGL
- No credit for lights (despite SALS)