Interesting GPS Experience Today

gvgoff99 · #1 01-28-2007, 10:04 PM

I have a Garmin 430. For the first time in my GPS experience I had the GPS attempt to take me to a point other than the one I expected. I dialed in KSAT for San Antonio from Houston and it put me on a "direct to" course. When I arrived I flew directly over Randolph AFB which was OK. I continued tooling on to KSAT as it appeared on the GPS. As I was looking out and keeping track of where I was in the San Antonio airspace I saw this big airport off to the front left of the "direct to" course and several miles short of the KSAT depicted on the GPS. I had been there a couple of other times and recognized that this was the real thing and landed without a problem.

Since I had been "cleared to land" it would have been bad form to fly past my destination. I imagine that the tower was wondering what the heck I was doing flying a right base to final instead of a straight in approach. Oh well, but interesting. I have never had that happen before and wonder why it happened. Did anyone else have a GPS glitch in mid-Texas today or was it just me that the feds were trying to loose

? Just because a person is paranoid it doesn't mean that someone is not out to get you

!

Ironflight · #2 01-28-2007, 10:18 PM

George - I was out in New Braunfels this afternoon, and the 430 got me there without a hitch. Did you happen to see what the GPS was telling you as to range and direction to go after you had landed? It actually sounds like you might have been headed for the VOR, instead of the field....I wonder if the database has a glitch between "KSAT" and "SAT" this month?

Paul

dan · #3 01-28-2007, 10:32 PM

You sure you didn't accidentally tune in SAT (the VOR) as opposed to KSAT (the airport)? They're not co-located and that might explain things...?

Harold Lanfear · #4 01-29-2007, 04:56 AM

I personally know of two cases where GPS has provided 'bad' info - the first happened to me a couple of years ago when I was flying locally (meaning; for once, I knew exactly where I was

) and the GPS told me I was 12 miles West of there. Apparently, testing was going on.

The second; was to my boss, who was in Washington DC, late at night, when the GPS started giving data that obviously wasn't right. ATC told him there were tests being run. He had to fly by visual references and get vectors.

I love GPS, but I don't fully trust it - meaning, I always carry, and use, a Sectional. Also, I just recently wrote to Jep regarding Class D airspace in Wilmington, DE; Teterboro, NJ and Caldwell, NJ which was obviously a differnent diameter that shown on the GPS by about a mile. Jep told me that some GPS manufactureres plug in a 'standard' 5 mile circle for Class D

. I was very surprised and now make sure that I measure airspace radius and write in on the sectional (We have a panel mounted, well-known, expensive, major brand GPS in the machine I fly in case anybody is wondering.)

GPS - Love it, Use it, but be cautious and retain those basic skills we learned long ago!

H

gvgoff99 · #5 01-29-2007, 10:19 PM

The first thing that I thought of was "am I going to the VOR?" I dismissed that pretty quickly because I knew that the VOR was (still is) just about directly north of the airport. If you take a look at the sectional (here is a link to an online sectional: http://skyvector.com/ I was being directed to about where the "T" is in Twin Oaks. The course was about half way between the VOR and the airport and the end point was about 5 or 6 miles west.
Paul, I saw your flight report posted and was wondering if you had any similar experience. I guess not. I did not notice the direction and distance after landing. I was glad to be on the ground without pulling too dumb of a stunt and violation.
I have had the 430 take me to mid Alabama from Houston spot on. I really do not know what happened. I'll be going again. The first time I went I was vectored to the VOR. This time I was cleared for a straight in to RW 30L. I was pretty much lined up for a fly by and a wave at the CT before I noticed the error. I wonder if they would have appreciated the RV grin?

Ironflight · #6 01-29-2007, 10:43 PM

I think I remember seeing a NOTAM about inaccuracy in GPS signals within a 350 nmi radius of Holloman over the weekend, but that's a long way from SAT George. I doubt that is relavent....

I remember years ago when I had an early handheld GPS, it sometimes lost lock on the birds (the constellation wasn't complete), and I'd get some strange positions and speeds - but I haven't seen that happen for many years now.

Paul

Brian Denk · #7 01-30-2007, 06:16 AM

I was out buzzing around west of my home base, over the Acoma Indian Pueblo. My Lowrance Airmap 300 totally lost signal. Never happened before. I mentioned it to a Navajo native I work with. His reply, "Don't fly over the res....."

Maybe the spirits didn't want me disturbing their airspace.

Geico266 · #8 01-30-2007, 09:14 AM

Well, I punched in KSAT into my 396 and got the same GPS coordinates as published in AirNav, and it looks like the line goes directly to the center of San Antonio Airport.

Hmmm.. when you punched in KSAT into your 430 did it take you to the airport (on the screen) or did it take you 5 miles away? Where did the follow me "line" go? To the airport or to the mis destination?

This is really weird.

Louise Hose · #9 01-30-2007, 09:27 AM

I experienced problems with both of my GPS units on Saturday (27th) morning while flying near and into KROW (~90 ENE of Holloman). First, the Tru-Trak ADI GPS was intermittently working right, going blank, and giving the very wrong direction. Worse than useless. I had seen this happen before (again, while flying near Roswell), but I thought the instrument was the problem. While I've seen GPS problems "near" Holloman before, I hadn't seen it within 2000' AGL.

I had my Garmin 195 turned off for more challenging IFR practice, but turned it on to see what happened. (In the past, the 195 seemed more immune to Holloman's activities than the ADI and had never failed me.) It couldn't lock into many of the satellites that should have been available. At that point, I hoped it was Holloman. If so, they were doing something much more intense/effective than I've seen before.

gvgoff99 · #10 01-30-2007, 10:02 AM

Quote:

Originally Posted by Geico266

when you punched in KSAT into your 430 did it take you to the airport (on the screen) or did it take you 5 miles away? Where did the follow me "line" go? To the airport or to the mis destination?

The 430 made its usual line to the destiantion and positioned KSAT at the end of the line. It is wierd because the end of the line and GPS indicated KSAT were not where the actual KSAT is located. I don't think that I will ever figure it out. I should have spent more time on the ground trying to figure it out before I shut down.