Joined: 10 May 2008 Posts: 86 Location: Pittsburgh Pennsylvania
Where Am I: Warning Tue Jul 01, 2008 6:23 pm
I mentioned this in another thread but feel that it is important enough to warrant its own thread. Be cautious with the Where Am I function. When I do a where am I from my home it gives a street address that is 15 houses away. That does not surprise me. The address data base is seldom correct. But what does concern me is the nearest intersection information that it provides. I live .3 miles from a major numbered state highway and my street intersects it. But for the nearest intersection, the Where Am I function gives an intersection of 2 minor suburban roads that are 2.5 miles as the crow flies or 4 miles by driving from my house.
I have tried the function in other areas and it appeared to work OK but it does not work for my home.
If you are reporting an accident in an area you are not familiar with, tell the emergency operator that you have a GPS and give them the coordinates. You can also provide the other information but I think it would be wise to caution the operator that the other information is subject to error. If you have good sky, your coordinates will be accurate to probably better than 50 feet. Who knows what the data base address and intersection information will provide.
Joined: 10 Jul 2008 Posts: 308 Location: Bay Area, California
Mon Aug 25, 2008 4:24 pm
I'd noticed it usually way off. Not just the address, but as you have stated, the nearest intersection is sometime ridiculously off, giving a location that is many miles a way???
If you have a cheaper Nuvi and the "Where Am I" feature is not available, what's the best way to find out exactly where you are in an emergency situation?
Joined: 10 Jul 2008 Posts: 1227 Location: Southern California
Mon Aug 25, 2008 7:11 pm
In addition to what Tim suggested to get the intersection, you can also get the GPS coordinates of your current position by simply touching your vehicle icon on the map screen (either 2D or 3D map mode). This will bring up a "save current position as a favorite?" screen which will display the GPS coordinates which can be given to emergency personnel to pinpoint your position.
This has been verified on a nuvi 200 and both a 750 and a 760 (in addition to the 7xx's "Where Am I?" function).
In addition to what Tim suggested to get the intersection, you can also get the GPS coordinates of your current position by simply touching your vehicle icon on the map screen (either 2D or 3D map mode). This will bring up a "save current position as a favorite?" screen which will display the GPS coordinates which can be given to emergency personnel to pinpoint your position.
This has been verified on a nuvi 200 and both a 750 and a 760 (in addition to the 7xx's "Where Am I?" function).
Is this trick much more accurate than the "Where Am I" feature?
Joined: 10 Jul 2008 Posts: 1227 Location: Southern California
Mon Aug 25, 2008 10:10 pm
The accuracy between the two is going to depend on each of the unit's GPS accuracy at that point in time and is negligable as I have just verified. One difference between the two is that the 7xx series continuously updates the coordinates & elevation while on the Where Am I screen while the 200 creates in essence, a snapshot of the exact point in time when the vehicle icon was touched.
Joined: 13 Mar 2008 Posts: 263 Location: Winter Springs, FL
Tue Aug 26, 2008 12:28 am
I've done a lot of boating and have given out and recorded a ton of lat/lon positions. They're easy to screw up. I couldn't imagine getting all those numbers right under the stress of an emergency. Plus, the person I'm reading them to has to get them right. I'd stick with an intersection or address.
Joined: 10 May 2008 Posts: 86 Location: Pittsburgh Pennsylvania
Emergency Reporting Tue Aug 26, 2008 2:28 am
HappyFunBoater wrote:
I've done a lot of boating and have given out and recorded a ton of lat/lon positions. They're easy to screw up. I couldn't imagine getting all those numbers right under the stress of an emergency. Plus, the person I'm reading them to has to get them right. I'd stick with an intersection or address.
I agree with the above advice only if you know where you are at. If you do not know where you are at, relying on the goofy information that is displayed in the map data set could cost valuable time, and possibly some one's life. Yes the map will show you exactly where you are at, but too often the roads are named incorrectly. I have lived in my home for 31 years and I have never heard of some of the road names that my Nuvi displays in my immediate area. Then it changes the road names depending on how you get on the road. The Nuvi map data is extremely inaccurate in my area.
The coordinate information is dead accurate and should be no more difficult to give than two telephone numbers. Make sure that you note the format of the numbers to the operator, and have the operator read them back to you including degree signs and decimal points.
I have done lot of Geocaching and yes on rare occasions, have transposed a number. But no one's life was at stake--plus I was keying it into the GPS using the klunky number entry system on a Garmin 76S. I think I would be far more careful in an emergency situation. Using care and having the operator read the number back is a far better solution than
sending the emergency responders on a map error induced wild goose chase.
Joined: 13 Mar 2008 Posts: 263 Location: Winter Springs, FL
Re: Emergency Reporting Tue Aug 26, 2008 2:49 pm
Navxnut wrote:
I agree with the above advice only if you know where you are at.
I don't know about that. Just looking at the map, checking for the closest major roads, and then saying "I'm 2 miles east of the intersection of x and y" seems pretty foolproof. The chance of a map error seems slimmer than me transposing two numbers. But if I had my wits about me and wasn't sitting in a burning car with an arm ripped off then I'd certainly follow up with the lat/lon.
Just did a Google search on the subject and copied down the following:
"Basically, every cell phone is constantly pinging radio frequencies to nearby towers, saying “here I am, send me a signal..” By tracking these pings sent to different cell towers, you can effectively track the position of a mobile phone to within 3-9 feet. This also means, that you can effectively track the position of anyone with a cell phone."
Joined: 13 Mar 2008 Posts: 263 Location: Winter Springs, FL
Tue Aug 26, 2008 7:38 pm
WhichWayAjay wrote:
Just did a Google search on the subject and copied down the following:
"Basically, every cell phone is constantly pinging radio frequencies to nearby towers, saying “here I am, send me a signal..” By tracking these pings sent to different cell towers, you can effectively track the position of a mobile phone to within 3-9 feet. This also means, that you can effectively track the position of anyone with a cell phone."
Sorry, I'm not shooting the messenger, but WHHAAAAAAAAAT?!?! That's better accuracy than GPS, probably done with fewer reference points in the calculation, and it will work indoors. GPS companies should immediately go out of business, or relagate themselves to offshore boating and folks living in the boonies. Does anyone have a phone (maybe an iPhone) that will display the lat/lon? I'd love to see a comparison with a GPS. Maybe I'll consult The Google...
[quote="HappyFunBoater"]Sorry, I'm not shooting the messenger, but WHHAAAAAAAAAT?!?! That's better accuracy than GPS, probably done with fewer reference points in the calculation, and it will work indoors. GPS companies should immediately go out of business, or relagate themselves to offshore boating and folks living in the boonies. Does anyone have a phone (maybe an iPhone) that will display the lat/lon? I'd love to see a comparison with a GPS. Maybe I'll consult The Google[/quote]
Yep, the iPhone already has quite a few apps for GPS. Here's a link to the first one in the App Store. http://www.instamapper.com/iphone
Joined: 13 Mar 2008 Posts: 263 Location: Winter Springs, FL
Tue Aug 26, 2008 8:18 pm
GadgetGuy2008 wrote:
Yep, the iPhone already has quite a few apps for GPS. Here's a link to the first one in the App Store. http://www.instamapper.com/iphone
Amazing what cell phones can do now.
Correctly me if I'm wrong, but I think the new iPhone has a real GPS chip using satellite information in addition to the cellphone tower triangulation. It was the accuracy of the triangulation that I was calling into question. The link above indicated 3-9 feet, but other links indicate 100-300 feet. As I keep reading it's becoming clear that these folks often confuse whether the phone has a real satellite GPS receiver or just does the tower triangulation. And I'm sure to a user it doesn't really matter how the magic is done, just as long as the paramedics find them in time. But I haven't found anything that indicates triangulation has any accuracy approaching that of a real GPS.
Does anyone have a phone (maybe an iPhone) that will display the lat/lon?
I have an iPhone 3G... doesn't come close to my "traditional" GPS devices as far as accuracy or speed of getting a fix. I mean it isn't like it is off by several hundred feet.... certainly should be accurate enough for road navigation once the API adds heading and speed values to the current variables.
Joined: 10 Jul 2008 Posts: 308 Location: Bay Area, California
Wed Sep 03, 2008 8:05 pm
I thought all new phones had to be E911 Compliant (with GPS); As such, had a GPS **receiver chip,** and sent the data (not the Lat/Long, but a long string of numbers) to the cell site, and their, it decoded the data, that was too processor and battery hungry, to be done in the cell phone, then if needed, was used as GPS position info - Lat/Long (for; turn by turn directions, or "Hay, don't you want a BigMac, today, next exit is McD's" Or 911 (CHP) Dispatch, "I see you at Hwy-1 and Ocean St?"...
The old system, used the knowledge of what cell sites, sectors, antennas, saw you (your cellphone, even if no call was being made), and you're RSSI, BER, or whatever, to find you, within ~1K feet (maybe less, if cell site coverage, was small) or maybe a 1 mile, depending on the cell sites used.
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