wgrupp

Hi,

Took a road trip this weekend and the car performed great. My biggest problem was my wife telling me to slow down :-) My Escort radar detector saved my ass 3 times.

While I was driving in the mountains around Yosimite I got a message on the Nav saying that no guidance was available for a several mile section of road. Once I got out of that area it started working again. During the time no navigation was available it still tracked my position on the map but just didn't give me any directions. Anybody else seen this?

Wayne

530E60NL

I've had this to in a part of Germany where my GPS had problems finding my correct location.

5 Rakete

If the terrain you are passing through is masking your line of sight to the GPS satellites currently overhead you will have degraded or no navigation solution. A minimum of 3 satellites are required for a 2-D solution and 4 for a 3-D solution (includes altitude). The more satellites in view the better the precision. Up to 12 satellites can be in view but those low on the horizon will be subject to masking. Even satellites well above the horizon can be masked if you are in a canyon or adjacent to some large terrain feature. Another thing to consider is that GPS signals are braodcast at a relatively low power being effectively omin-directional (with respect to the surface of the Earth). That means that significant overhead canopies of foilage and surrounding tree trunks can prevent reception.

noonehome

I've experienced it twice. The first time I was at a large hydro electric Dam in Eastern Washintington State, where it is pretty wide open. The " no navigation" appeared as soon as I enter the property pate and navigation resumed as soon as I left the gate. I suspect signal jamming but don't really know.

paasan

Signal jamming happens about once a year where I live.. that is whenever the airforce up here practice jamming missile systems and so on

At these times its usually printed in the local newspaper that GPS and radars may for some time provide inaccurate information, or no valuable information at all.

Rudy

I've had this happen a couple times in the same areas. I'm sure it's not related to GPS signal -- I think it has something to do with incomplete data from NavTeq.

When I had it happen to me, the car knew where I was in terms of latitude and longitude, it knew what road I was on, etc. but it simply couldn't handle the instructions for where and when to turn next. You could even see the map display was showing where I was on the road -- I didn't get the "outside of digitized area" message.

Both times, it was in an area that was not on even on the map last year. I think there are many layers of data on the disc and unless all of them are present, the car can't do everything it needs to do.

Most likely, NavTeq is adding data layer by layer so since last year's disc didn't have any information and this year's disc has some, I'm betting this problem will go away with each new release.

Anyone upload the new DVD yet?

5 Rakete

Intentional jamming is a real possibility, either sanctioned (military) exercises or experiments or malicious activity. A crude but effective noise signal masking jammer is easily built. Unintentional jamming also occurs. Electronic devices emit radio frequency energy at frequencies intended for their operation but also on harmonic frequencies at much lower power. Poorly designed or out of spec equipment can be a problem and even low power emissions in the GPS frequency spectrum can override or mask the real signal especially for systems like ours that have omni-directional antennas. Such inintentional jamming can affect receivers a mile away. A crude intentional jammer could affect receivers many miles away.

Spadoc

I've noticed that it also depends on your route preference choices. If I'm in a rural area and have selected "fastest", the display often says no guidance available. If I swith to shortest, it changes the route and has no trouble.

Rudy

Interesting...I'll have to try that next time! I suppose it supports my theory that there is some data lacking somewhere, doesn't it?

Thanks!!