GPS DME VS DME

[B737NG_Pilot]

In terms of Navigation, which one is more accurate. GPS approach or DME based approach.

[this is my username]

You are trying to compare apples with oranges - DME distance and GPS distance are different things. If the approach calls for you to use DME then that is what you should use. If the approach uses GPS then you should use GPS. You shouldn't substitute one for the other.

[B737NG_Pilot]

I agree. But point is accuracy that's all.

[charliegolf]

Is a DME reading not a slant height, therefore reading further away than a GPS range from the same spot over the ground?

CG

[Racing Snake]

Gps is the most accurate

[Mach Jump]

Using GPS range on a GPS approach is generally more precise than using DME range on a DME approach.

Mix and match at your peril!:eek:


MJ:ok:

[paco]

"Gps is the most accurate"

And yet the FMS will take a DME/DME fix in preference.

phil

[Fieldmouse]

Often refer to different places on the airfield too. The DME can be located 2Nm or more from the ARP which is the GPS reference point.

[FLAPS RUNNING]

GPS approach. GNSS APR approaches require an accuracy of 0.1 NM and are often more accurate. Ours always seem to be accurate to 0.05nm .DME/DME still very accurate and all that's required for RNAV 1.

[GlenQuagmire]

I have three IRS's on board and an FMS that will take information from every available position source - DME/DME, VOR/DME etc and if I look at the sensor page the one it is actually using is the GPS. It seems that as long as the GPS is in agreement with the others the FMS is actually using the GPS position. So I suspect that the GPS is the most accurate. I use it for precision approaches so it bloody better be!

[paco]

Thanks for that - useful information....

Phil