Just so a post regaring setting/Align the IRS and I always use airport pos for setting IRS Pos/int side1/4, but this guy says that using the GPS on Pos/int side 2/4 is the correct regarding that airport pos is not always corect depending were you are on the airport?Ok what to use airport pos or GPS pos for setting IRS............

You should use GPS because it is the actual position of the aircraft. The airport position it will always be different.And since we are talking about this, i don't know if you guys had checked this out, but even if i load a saved panel state, the actual position it is always the actual position and not the previous position. Maybe i'm mistaken but, shouldn't be the last position where the aircraft was parked?

I always use GPS POS ... RTE Page 2

I always use the gate position, although that is not always an option if it is not coded in the database. That is the most accurate because you are in a known position, and confirmed coordinates.While GPS position is almost 99.99% of the time exactly the same as the gate coordinates, you are relying on something that could be off a little. That is why all Jepp 10-9 pages have the gate coordinates. A lot of big airports also have the coordinates published next to the gate number or name so you can see them from the cockpit. If not, you just revert to the 10-9 pages. The only times I've seen a bit of map shift with GPS signals a bit out of whack has been in Seoul and in Taipei. I figured it was the paranoia of the Koreans or the Taiwanese messing with GPS signals for fear of an attack during a military exercise or something along those lines.Interestingly, if you where aligning your IRUs in Japan right after the quake by using the published gate coordinates instead of the GPS, you would have been 6 meters off on your actual position. The whole country shifted after the quake, that is how bad it was. One of the few times where GPS would have actually been more accurate than the gate position.

I always use the gate position, although that is not always an option if it is not coded in the database. That is the most accurate because you are in a known position, and confirmed coordinates.While GPS position is almost 99.99% of the time exactly the same as the gate coordinates, you are relying on something that could be off a little. That is why all Jepp 10-9 pages have the gate coordinates. A lot of big airports also have the coordinates published next to the gate number or name so you can see them from the cockpit. If not, you just revert to the 10-9 pages. The only times I've seen a bit of map shift with GPS signals a bit out of whack has been in Seoul and in Taipei. I figured it was the paranoia of the Koreans or the Taiwanese messing with GPS signals for fear of an attack during a military exercise or something along those lines.Interestingly, if you where aligning your IRUs in Japan right after the quake by using the published gate coordinates instead of the GPS, you would have been 6 meters off on your actual position. The whole country shifted after the quake, that is how bad it was. One of the few times where GPS would have actually been more accurate than the gate position.

It's easy, insert your airport on that page and check the coordinates on the FMC with the coordinates that shows on screen after pressing Shift + Z and see which one it is more accurate. I think you have to press it twice.Edited to change Ctrl + Z to Shift + Z

Edited October 24, 201114 yr by masneoquil

The last airline I flew at didn't even bother putting the gate info in the FMC. We always used GPS. My current airline we use GPS first and then gate info, 10-9 info, or coords from the chart.When I was flying in Asia, I think GPS was preferred because Chinese coordinates and data were suspect. You could punch in the GPS coords, and you'd show up off-airport.