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Cellular forums Home > Archive > Garmin GPS > December 2006 > Whatever happened to dead reckoning?
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Whatever happened to dead reckoning?
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| Ramon F Herrera 2006-11-24, 10:33 pm |
| Is dead reckoning, well, err, dead?
It seems that Garmin is not selling GPS with dead reckoning anymore.
Does the competition have it?
Not that I care much for it. I have driven in all the big US cities and
the only one where you really need it is in Manhattan.
-Ramon
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| Seagull 2006-11-25, 4:33 am |
| In alt.satellite.gps Ramon F Herrera <ramon@conexus.net> wrote:
> Is dead reckoning, well, err, dead?
It's alive and well but mostly in built-in car systems and in-dash
aftermarket units from Pioneer, Alpine, etc.
> It seems that Garmin is not selling GPS with dead reckoning anymore.
The 7500 has it.
Cheers,
John
--
\ carpe cavy!
seagull @ aracnet.com \
http://www.aracnet.com/~seagull/ \ (seize the guinea pig!)
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| mike vore 2006-11-25, 10:33 pm |
| Ramon F Herrera wrote:
> Is dead reckoning, well, err, dead?
You mean DED Reckoning - Deduced reckoning - taking a SWAG as to where you
are. DEC Reckoning is one method of navigation, GPS is an aid to navigation
where one gets occasional (with good signals Quite Often) fixes.
Ded Reckoning - hmmm I started at Point A, went (about)northeast for 10
minutes at 35mph, so without anything putting me off course I should be at
Point B - Now let's get a Fix, and see where I really am. hmmm, close. Ok
correct my course and/or speed guess and go from Point (new)B towards C.
--
Mike Vore
http://www.OhMyWoodness.com
http://mike.vorefamily.net/twr
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| peter 2006-11-25, 10:33 pm |
| mike vore wrote:
> Ramon F Herrera wrote:
>
> You mean DED Reckoning - Deduced reckoning - taking a SWAG as to where you
> are. DEC Reckoning is one method of navigation, GPS is an aid to navigation
> where one gets occasional (with good signals Quite Often) fixes.
No, "dead reckoning" appears to be the correct form, at least according
to the Oxford dictionary eytymology and Wikipedia:
http://en.wikipedia.org/wiki/Dead_reckoning
Calling it "ded" for deduced seems to be a rather recent corruption of
the previous term.
Most GPS units have some form of dead reckoning, e.g. Garmins generally
continue showing your position incrementing as it was before for 30
seconds after a loss-of-signal, and many of the built-in automotive
units have a more sophisticated dead-reckoning feature using magnetic
compass sensors and a speedometer output to continue navigating while
in tunnels or in tight urban (or natural) canyons where reception is
blocked for extended periods. Of course errors will eventually build
up and make such navigation inaccurate, but it can be of significant
help in some environments.
Garmin has been offering this enhanced dead-reckoning feature on some
of their automotive models starting with the 2650/2660, but I don't
think it ever captured much of that market. Since it required physical
connection to the car wiring Garmin first insisted that those units be
purchased only from authorized installers. That made the units
relatively high-priced compared to their other models which were
subject to more competitive pricing by dealers.
Their current 7500 model has simplified the process so dealer
installation is no longer needed.
Better GPS receiver circuitry has also reduced the need for the
enhanced dead-reckoning feature.
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| Ramon F Herrera 2006-11-26, 12:33 pm |
| mike vore wrote:
> Ramon F Herrera wrote:
>
> You mean DED Reckoning - Deduced reckoning - taking a SWAG as to where you
> are. DEC Reckoning is one method of navigation, GPS is an aid to navigation
> where one gets occasional (with good signals Quite Often) fixes.
>
I am sure that "DED" has to be a marketing euphemism. Some marketing
guy (those who wear togas and hire harpists to conjure muses in
Dilbert) decided that it was a bad idea to sell a product with the word
"dead" to navigators.
Its the same case as "RAID", which stands for "Redundant Array of
Inexpensive Disks", but the word "Inexpensive" has been euphemistically
replaced by "Independent" in some quarters.
-Ramon
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| peter wrote:
> Most GPS units have some form of dead reckoning, e.g. Garmins
> generally continue showing your position incrementing as it was
> before for 30 seconds after a loss-of-signal, and many of the
> built-in automotive units have a more sophisticated dead-reckoning
> feature using magnetic compass sensors and a speedometer output to
> continue navigating while in tunnels or in tight urban (or natural)
> canyons where reception is blocked for extended periods.
I thought some of the TomTom models had dead reckoning via internal
sensors -- i.e., no need to hook anything up.
I was disappointed that my new (and otherwise awesome) Nuvi 660 still
says "Lost Satellite Reception" when going through tunnels. It should
know how to calculate when I enter the tunnel going X mph, and the
tunnel is Y miles long, generally how long it should keep its clap shut.
In that respect it acts just like the SPIII did back in the Jurassic
era.
--
JC
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| Ramon F Herrera 2006-12-08, 7:33 am |
|
JC wrote:
> peter wrote:
>
> I thought some of the TomTom models had dead reckoning via internal
> sensors -- i.e., no need to hook anything up.
>
> I was disappointed that my new (and otherwise awesome) Nuvi 660 still
> says "Lost Satellite Reception" when going through tunnels. It should
> know how to calculate when I enter the tunnel going X mph, and the
> tunnel is Y miles long, generally how long it should keep its clap shut.
> In that respect it acts just like the SPIII did back in the Jurassic
> era.
>
I think you are asking for too much, JC. They would need to place a
gyroscope and an accelerometer inside that little box.
http://en.wikipedia.org/wiki/ Inert...e_sy
stem
-Ramon
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| B A R R Y 2006-12-08, 7:33 am |
| JC wrote:
> I was disappointed that my new (and otherwise awesome) Nuvi 660 still
> says "Lost Satellite Reception" when going through tunnels. It should
> know how to calculate when I enter the tunnel going X mph, and the
> tunnel is Y miles long, generally how long it should keep its clap shut.
> In that respect it acts just like the SPIII did back in the Jurassic
> era.
>
It DID lose satellite reception. <G>
I would much rather know that it doesn't have a sat lock, rather than
have it guess why and try to decide if I need to know. Some of RF is
reflected into the tunnel, so you have some sort of a signal at both
ends. This means you keep a lock as you enter, and at least on my
current units, regain it quickly at the other end. Big deal...
If you can manage getting from one end of the tunnel to the other
without getting lost, you should be fine.
Really need to know what direction you're headed in underground? Many
of the magnetic compass equipped units will at least give you a
directional reading without a lock.
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| Ramon F Herrera 2006-12-08, 3:33 pm |
|
B A R R Y wrote:
> JC wrote:
>
> It DID lose satellite reception. <G>
>
> I would much rather know that it doesn't have a sat lock, rather than
> have it guess why and try to decide if I need to know. Some of RF is
> reflected into the tunnel, so you have some sort of a signal at both
> ends. This means you keep a lock as you enter, and at least on my
> current units, regain it quickly at the other end. Big deal...
>
> If you can manage getting from one end of the tunnel to the other
> without getting lost, you should be fine.
>
> Really need to know what direction you're headed in underground?
DR is very useful when you find yourself inside cannons -in Manhattan
or in Yellowstone.
-Ramon
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| John Richards 2006-12-08, 3:33 pm |
| "Ramon F Herrera" <ramon@conexus.net> wrote in message news:1165576243.495109.248570@j44g2000cwa.googlegroups.com...
>
> JC wrote:
>
> I think you are asking for too much, JC. They would need to place a
> gyroscope and an accelerometer inside that little box.
>
> http://en.wikipedia.org/wiki/ Inert...e_sy
stem
For short tunnels, it would only need to assume that the vehicle
continues in the same direction and speed as existed just prior
to loss-of-signal. No sensors required.
--
John Richards
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| B A R R Y 2006-12-08, 3:33 pm |
| Ramon F Herrera wrote:
>
> DR is very useful when you find yourself inside cannons
So you'll know where you're headed if someone fires it? <G>
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| Rudolpho 2006-12-08, 10:33 pm |
| B A R R Y wrote:
> Ramon F Herrera wrote:
>
> So you'll know where you're headed if someone fires it? <G>
Please have pity on people who aren't native speakers of the English
language.
--
Rudolpho
A program is never finished until the programmer dies.
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| Ramon F Herrera 2006-12-11, 7:33 am |
| JohanE wrote:
> "John Richards" <jr70@blackhole.invalid> wrote in message
> news:wojeh.1436$Gr2.75@newssvr21.news.prodigy.net...
ut.[color=darkred]
>
> This is exactly what TomTom does, for about a minute or so, which is enou=
gh
> for the river-tunnels here in Holland. It assumes you continue on the same
> road, at the same speed. The screen does turn to monochrome to indicate
> signal loss.
>
> JohanE
The Garmins do that as well (and most likely Magellan), but that is not
Dead Reckoning because it is based on two simplistic assumptions which
do not hold true in the general case. I have driven more than 70K miles
all over the USA and particularly remember two places where the loss of
signal was a PITA: Manhattan and some Vermont forest.
Compared to the StreetPilot, the n=FCvi has better sensitivity to the
NAVSTAR signals. Sometimes I have left my n=FCvi in the passenger seat
and it keeps on working.
-Ramon
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| kdarling@basit.com 2006-12-17, 10:33 pm |
|
Ramon F Herrera wrote:
>
> I am sure that "DED" [reckoning] has to be a marketing euphemism.
> Some marketing
> guy (those who wear togas and hire harpists to conjure muses in
> Dilbert) decided that it was a bad idea to sell a product with the word
> "dead" to navigators.
I believe you're exactly right. The first use of "ded" instead of
"dead" came about in the early 1930s in books aimed at aircraft pilots.
I think they hoped that putting a modern spin on the term would make
it seem more suited towards aviators.
Regards, Kev
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