earthmate is kinda off

julesbchillin · 11-11-2003, 11:50 AM

Im using an earthmate with street atlas 2003 and I find when I zoom in It shows that I m way off the actual street????It seems to be about 20 to 30 meters off. Is this normal????can I adjust it

hijinks21 · 11-11-2003, 12:46 PM

i found AA 2003 to really suck and every now and then i'd run into that problem

wizardPC · 11-11-2003, 12:56 PM

that's normal, and within the spec of GPS. you probably only have 3 or 4 satellite locks. The more locks you get, the more accurate your readings will be

julesbchillin · 11-11-2003, 05:07 PM

thanks alot.

mindtool · 11-19-2003, 11:58 PM

It's a matter of governmental control. The consumer GPS systems have an error althorighm that throws you off on purpose like +/- 2m up to 50m off target.

The reason behind this was for national security. How would you like it if some terrorist bought a $100 gps device and mounted it in a missile and launched it knowing that it would have facial pimple accurancy.

The military level of GPS systems are the SAME stuff that we consumers use just that their system uses a much different set of channels/protocols that don't have the error althorighm that allows them to have a dead-on accurancy of +/- 1 inch.

cproaudio · 11-20-2003, 01:55 AM

I dont think its the government crap. SA2K3 just plain sucks. What are the chances of it being 5 meters off 100% of the time at the exact same spot no matter what the sky condition is or how many satelites it's locked? The map is wrong. SA2K3 doesnt have position error correction like Copilot (while navigating) or most of the OEM navs do.

mindtool · 11-20-2003, 02:01 AM

I know for a fact that the government has error althorighms in place for ALL consumer GPS products but they're thinking of turning it off anyway but for that specific GPS product or software it probably is crappy.

Again, I do know that the government is regulating how GPS signals are sent to consumer GPS products because of national security issues. I know this because my Unc works for JPL (Jet Propulsion Lab - NASA) in California and he took a big part in the GPS development some 15-20 years ago for the military. He occasionally gets called back in to work on new projects along the way relating to GPS satellites and that being off by 5 meters is normal for consumer GPS products - no matter how good your GPS receiver is.

Once the government turns the error althorighm off, our same existing GPS devices would be accurate as the last pimple on your nose.

carabuser · 11-20-2003, 02:26 AM

julesbchillin, same here. I guess it's normal for the particular GPS/map software. I get the same thing. You (and I) should try other software with it.

As for the government regulation, I don't think it would be very effective. If a terrorist buys that thing and mounts it in a missile, I'm pretty sure it won't be fireworks, but rather something more powerful where 20-30 meters isn't an issue, since if it blows, it blows big time. Plus it's not always off, most of the time it's pretty accurate. So what's the point?

Spec-V · 11-20-2003, 09:57 AM

Ok let me clear this up for everyone.

I work for the US Coast Guard (now a civilian) and served on Active Duty for 6 Yrs.

There are two standards. GPS and DGPS.

GPS = As you all know, Global Positioning System

The government owns all of the GPS satellites. Hence they also own the transmissions that they send down to us here on the surface.

They add an algorithm to the transmission that makes it less accurate (+ or - 100yds)

This algorithm can be decoded by way of a DGPS receiver DGPS = Differential GPS. There are DGPS beacons (receiver/transmitter) all over the USA, mostly on the coast. The USCG uses DGPS to position Aids To Navigation (Buoys, Lights) on the waterways. DGPS is much more accurate (+ or - 10yds) This makes sense, being as buoys and lights mark shipping channels and other very important things.

The only way to receive a DGPS signal is to have a DGPS receiver/antenna. Then you must be in range of a DGPS beacon. Which is a Land Based high power antenna, that retransmits the GPS signal via radio.

That is why our USB and Serial GPS receivers are not super accurate.

mindtool · 11-20-2003, 11:09 AM

There you go carcomp! I know some stuff about GPS although I may not be accurate in some areas.

CoolDaddyAndy · 11-29-2003, 06:23 AM

I will also concur about the DGPS. But have used about 7 different GPS programs and have found SA v9 Deluxe, 2003, and 2004 all suck. There maps are way off. They are missing roads that have been around for over 10 yrs and they just arent drawn or even labelled correctly some times.
I use Iguidance, it's only $100.00 and It is very accurate as far as position and street labels. of course not all roads are going to be available since they change constantly but for the most part, it is accurate. This may be do to error correcting but I can testify that I will be only about 3-9 meters from the road and it shows me off the road. Everytime in the same position.
I have also used software to draw a line from my start positionn to my finish and if I go in a circle it brings me back to the same spot every time.
Whether (spelling) or not the government throws in a couple errors on purpose, just shell out a few extra clams for better software.
Allways look for the navtech logo. This will ensure quality map data at the least.