GPS OBS mode

Blip16 · March 5th, 2009, 10:26

is that True Course, or Mag Course?

Fly_Unity · March 5th, 2009, 10:32

Quote:

Originally Posted by BuickCFI

is that True Course, or Mag Course?

Im sure its Mag course, my GPS has the option to set it to true course, however why would you want to use True Course?

400A · March 5th, 2009, 10:51

Quote:

Originally Posted by Fly_Unity

Im sure its Mag course, my GPS has the option to set it to true course, however why would you want to use True Course?

When flying in the AMU (area of magnetic uncertainty), north of 73N I believe or maybe even 65N can't recall.

fish314 · March 5th, 2009, 13:08

Quote:

Originally Posted by 400A

When flying in the AMU (area of magnetic uncertainty), north of 73N I believe or maybe even 65N can't recall.

Or 'Grid'... Ohh, anyone use 'Grid' anymore. I used it once in the -135 (actually the nav did). Made my eyes bleed and I'm sure I went insane for about 10 minutes.

fish314 · March 5th, 2009, 13:08

Hey, what does the 'OBS' stand for anyways? observed? obsessed? obstetrics?

Blip16 · March 5th, 2009, 13:10

Quote:

Originally Posted by Fly_Unity

Im sure its Mag course, my GPS has the option to set it to true course, however why would you want to use True Course?

someone asked me the other day, and for the life of me i couldn't remember. i checked the manual and it didn't say. I said it was Mag but someone else told them it was true.

TFaudree_ERAU · March 5th, 2009, 14:06

Quote:

Originally Posted by fish314

Hey, what does the 'OBS' stand for anyways? observed? obsessed? obstetrics?

Omni Bearing Selector. Same as your good ole VOR head.

Blip16 · March 5th, 2009, 23:52

alright, i was right, it is MC. i checked it today. the bearing to the station was 118 according to the VOR but according to the GPS it was 122. the VOR here has -9 Variation so TC would have been 127 - 5 Variation = 122 MC.

sorry if that is confusing

MidlifeFlyer · March 6th, 2009, 07:34

Quote:

Originally Posted by BuickCFI

alright, i was right, it is MC. i checked it today. the bearing to the station was 118 according to the VOR but according to the GPS it was 122. the VOR here has -9 Variation so TC would have been 127 - 5 Variation = 122 MC.

sorry if that is confusing

More confusing than needed. VORs need to be recalibrated periodically, so for a VOR and GPS to show course differences is not that unusual.

Fly_Unity · March 6th, 2009, 15:16

Quote:

Originally Posted by BuickCFI

alright, i was right, it is MC. i checked it today. the bearing to the station was 118 according to the VOR but according to the GPS it was 122. the VOR here has -9 Variation so TC would have been 127 - 5 Variation = 122 MC.

sorry if that is confusing

I know its MC. Im confused though how you came to that conclusion with your above post

fish314 · March 6th, 2009, 17:54

Quote:

Originally Posted by MidlifeFlyer

More confusing than needed. VORs need to be recalibrated periodically, so for a VOR and GPS to show course differences is not that unusual.

Also, depending on the system, you may not get an updated deviation for the VORs in the database.

For our system, on a GPS approaches and GPS overlay approaches the courses calculated by the GPS system only need to be within 5 degrees of the courses printed on the chart.

Blip16 · March 6th, 2009, 22:31

Quote:

Originally Posted by Fly_Unity

I know its MC. Im confused though how you came to that conclusion with your above post

Variation around GFK is 5E. VOR Variation is 9E. so if my OBS is 118 i can add 9 and get a TC of 127 if i subtract Variation i arrive at the MC for my area which is what the GPS read.

does that make more sense?

Fly_Unity · March 7th, 2009, 20:31

Quote:

Originally Posted by BuickCFI

Variation around GFK is 5E. VOR Variation is 9E. so if my OBS is 118 i can add 9 and get a TC of 127 if i subtract Variation i arrive at the MC for my area which is what the GPS read.

does that make more sense?

wait... VOR variation is different the normal variation?

Blip16 · March 8th, 2009, 00:12

yeah? check the AFD, it isn't always, and there are a few VOR's around here with 0 variation.

firepilot68 · March 10th, 2009, 09:48

The BUF VOR has a different variation as well. It's variation is 8W, current Mag variation is 11W. I did a little researching, mag variation was 8W in 1965 when the VOR was installed.

I know that when you reference the VOR for a user defined waypoint you cannot use the VOR rose or else you will be 3º off. That is for the G430. It is on mag, but I believe you can change it to true.

400A · March 10th, 2009, 10:21

http://en.wikipedia.org/wiki/Magnetic_declination

March 5th, 2009, 10:26	#1
Blip16 Old Skool Join Date: Feb 2006 Location: Nowhere Good Posts: 2,845	GPS OBS mode is that True Course, or Mag Course? __________________ IFC, CIFI, EMI This is my Signature, I am supposed to put something here.

March 5th, 2009, 13:08	#5
fish314 Old Skool Join Date: Feb 2006 Location: Andover, KS Posts: 1,780	Re: GPS OBS mode Hey, what does the 'OBS' stand for anyways? observed? obsessed? obstetrics? __________________ Dude, what are you trying to do? Land the airplane or adjust the field elevation?

March 5th, 2009, 23:52	#8
Blip16 Old Skool Join Date: Feb 2006 Location: Nowhere Good Posts: 2,845	Re: GPS OBS mode alright, i was right, it is MC. i checked it today. the bearing to the station was 118 according to the VOR but according to the GPS it was 122. the VOR here has -9 Variation so TC would have been 127 - 5 Variation = 122 MC. sorry if that is confusing __________________ IFC, CIFI, EMI This is my Signature, I am supposed to put something here.

March 8th, 2009, 00:12	#14
Blip16 Old Skool Join Date: Feb 2006 Location: Nowhere Good Posts: 2,845	Re: GPS OBS mode yeah? check the AFD, it isn't always, and there are a few VOR's around here with 0 variation. __________________ IFC, CIFI, EMI This is my Signature, I am supposed to put something here.

March 10th, 2009, 09:48	#15
firepilot68 Newbie Join Date: May 2008 Location: BUF Posts: 9	Re: GPS OBS mode The BUF VOR has a different variation as well. It's variation is 8W, current Mag variation is 11W. I did a little researching, mag variation was 8W in 1965 when the VOR was installed. I know that when you reference the VOR for a user defined waypoint you cannot use the VOR rose or else you will be 3º off. That is for the G430. It is on mag, but I believe you can change it to true. __________________ Despite the cost of living, it’s still popular.

March 10th, 2009, 10:21	#16
400A Senior Member Join Date: Mar 2008 Location: MSP Posts: 610	Re: GPS OBS mode http://en.wikipedia.org/wiki/Magnetic_declination

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