Accuracy of landing position

[Navman]

I’m situated about 4 miles east of Cardiff Airport and get good coverage of Bristol just across the Bristol Channel. Flights landing at Cardiff are usually shown to land several hundred metres north of the runway and sometimes to the south but not on the runway. Flights into Bristol are shown very accurately positioned straight down the ILS and onto the runway. Can anybody explain why this is happening.

Navman 

[AirNav Support]

Two reasons why this might be happening:

1.) Aircraft has a offset from the GPS (one of its) and hence its showing in the incorrect position.

2.) The map may be out, you may want to check its position and confirm it.

Hope it helps.

[Navman]

I’ve checked the latitude and longitude on the centre of the runway as shown at the bottom of the screen and the map is spot-on. It could be something to do with a GPS offset, maybe that’s why aircraft are sometimes to the left or right but I don’t understand why I’m not seeing these errors at Bristol. Could it be that Bristol is line of sight and Cardiff is over the other side of a hill from me?

Thanks for your comments.

[AirNav Support]

Doubt it, its likely it a specfic aircraft/airline with the issue which you see landing in Cardiff.