Weird Readings

[+ADKcachers]

I had some strange readings on my GPSr (Magellan Sportrack) yesterday in the late afternoon in the Northeastern US.

 

It kept indicating that I was travelling at an incredible velocity. I was really doing

1-2 mph.

 

What the??

 

I didn't see any news anywhere about solar activity.

[2oldfarts (the rockhounders)]

It could have been low batteries.

Were there any black helicopters flying around the area?

Did you see any UFOs?

 

I vote for the batteries.

 

John

[+ADKcachers]

I thought that too, I switched out to fresh ones & got the same. Later in the afternoon it seemed to work fine.

[+TotemLake]

This is a common occurrence. Kerry can correct me if I'm wrong, but I've surmised that sometimes when the GPS receiver loses lock on one satellite going over the horizon, it picks up on another coming up from the horizon and because calculations haven't quite finalized with the new geometric dynamics, your GPS will show you to be at a location other than reality.

 

I've noted speeds up to 1500 MPH and a location zing of 1000 miles. It doesn't happen often, but the anomaly is so pronounced it produces an interesting track.

 

I've also seen the same thing happen as the GPS is losing lock and regaining it in a matter of seconds; usually due to heavy foliage, echoes from steep grades while you're in a valley or while you are in a downtown area of high rises.

 

As for the heavy foliage, I'm beginning to think it has more to do with how dense the forest is with trees than it is with the density of the leaves. That is, the tree trunks are what is causing the narrow window rather than the leaves blocking the signal.

[+Confucius' Cat]

I have had this happen from time to time, mostly with my Garmin Street Pilot mobile GPSr. It seems to occur most frequently in an area in central western Indiana where there a lot of trees near the road.

 

I suspect it is primarily a poor signal and reflection of signals phenomonon.

 

I have had readings suddenly change about 200 miles and then back resulting in velocities of nearly 1500mph. shortly thereafter the receiver would lock up and the screen said "receiver unuseable, power down and restart".

 

I have also had very high speed readings with the internal antenna inside the vehicle. That is one reason I have the active antenna outside. Doesn't happen very often anymore.

[+ADKcachers]

Thanks guys, I was in an area with lots of trees and hills, valleys, etc. I had visions of sending my unit out for repair.

[+Quadcache]

Aren't GPS sats. in a geosyncronous orbit? Meaning they don't revolve around the earth but stay in the same spot?

[+zygote2k]

I got a really weird reading the other day- it was an e-mail from "Sparky-Watts"!

[+TeamK-9]

I got a really weird reading the other day- it was an e-mail from "Sparky-Watts"!

Leave Sparky alone...

[+zygote2k]

On a more serious side- if you want to know all about GPS, go to www.trimble.com This is what GPS is all about.

[Kerry.]

Aren't GPS sats. in a geosyncronous orbit? Meaning they don't revolve around the earth but stay in the same spot?

Oh no, they move alright, the system simply wouldn't work if they didn't orbit. They travel at something like 4000m/s and effectively orbit the earth twice a day.

 

As for the 1500mph, GPS isn't perfect, no measuring system is and what the other unknown 5% of the accuracy specifications tend to cover, the unexpected for whatever reason. Another reason why the specifications are for Signal In Space (SIS) conditions as one has no control how the user will/might implement/use things at their end.

 

Cheers, Kerry.

[+Geo Ho]

I have a little yellow E-trex . . . these phenomena are a fact of life for me . . .

 

Heck! It makes looking for a cache that much more challenging! Heh!

 

Happy caching and stuff!