Empathy List Archives

E

ehydra

Thu, Nov 24, 2011 12:01 PM

Hi all!

I wonder what would be reasonable location accuracy if two cheap same
type GPS modules will be several meters apart? I understand that it
involves statistical numbers.

Any idea? Say for a small robot.

Thanks!

Henry

--
ehydra.dyndns.info

Hi all! I wonder what would be reasonable location accuracy if two cheap same type GPS modules will be several meters apart? I understand that it involves statistical numbers. Any idea? Say for a small robot. Thanks! - Henry -- ehydra.dyndns.info

AB

Azelio Boriani

Thu, Nov 24, 2011 1:47 PM

Usually GPS receivers have DOP figures you can use to estimate the position
precision. Maybe worth using timing receivers for position to increase the
position accuracy.

On Thu, Nov 24, 2011 at 1:01 PM, ehydra ehydra@arcor.de wrote:

Hi all!

I wonder what would be reasonable location accuracy if two cheap same type
GPS modules will be several meters apart? I understand that it involves
statistical numbers.

Any idea? Say for a small robot.

Thanks!

Henry

--
ehydra.dyndns.info

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Usually GPS receivers have DOP figures you can use to estimate the position precision. Maybe worth using timing receivers for position to increase the position accuracy. On Thu, Nov 24, 2011 at 1:01 PM, ehydra <ehydra@arcor.de> wrote: > Hi all! > > I wonder what would be reasonable location accuracy if two cheap same type > GPS modules will be several meters apart? I understand that it involves > statistical numbers. > > Any idea? Say for a small robot. > > Thanks! > - Henry > > > -- > ehydra.dyndns.info > > ______________________________**_________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > and follow the instructions there. >

E

ehydra

Fri, Nov 25, 2011 5:26 AM

I read that for position accuracy ionospheric effects are the main
source for typical single frequency receivers. So looking for DOP would
be not helpful because the ionospheric way is for two 'relative' on the
same position located teceivers vs. satellites position almost the same
and that would cancel this error source out!? The end-effect should be
better values than seen in the datasheet.

I must ask again. More opinions?

Henry

Azelio Boriani schrieb:

Usually GPS receivers have DOP figures you can use to estimate the position
precision. Maybe worth using timing receivers for position to increase the
position accuracy.

On Thu, Nov 24, 2011 at 1:01 PM, ehydra ehydra@arcor.de wrote:

Hi all!

I wonder what would be reasonable location accuracy if two cheap same type
GPS modules will be several meters apart? I understand that it involves
statistical numbers.

Any idea? Say for a small robot.

Thanks!

Henry

--
ehydra.dyndns.info

I read that for position accuracy ionospheric effects are the main source for typical single frequency receivers. So looking for DOP would be not helpful because the ionospheric way is for two 'relative' on the same position located teceivers vs. satellites position almost the same and that would cancel this error source out!? The end-effect should be better values than seen in the datasheet. I must ask again. More opinions? - Henry Azelio Boriani schrieb: > Usually GPS receivers have DOP figures you can use to estimate the position > precision. Maybe worth using timing receivers for position to increase the > position accuracy. > > On Thu, Nov 24, 2011 at 1:01 PM, ehydra <ehydra@arcor.de> wrote: > >> Hi all! >> >> I wonder what would be reasonable location accuracy if two cheap same type >> GPS modules will be several meters apart? I understand that it involves >> statistical numbers. >> >> Any idea? Say for a small robot. >> >> Thanks! >> - Henry >> >> >> -- >> ehydra.dyndns.info -- ehydra.dyndns.info

CA

Chris Albertson

Fri, Nov 25, 2011 6:43 AM

I think the accuracy could be quite good if you took advantage of the
times the robot was motionless. During those times it could build up
many seconds of averaging and then while moving either use dead
reckoning or inertial navigation.

On Thu, Nov 24, 2011 at 4:01 AM, ehydra ehydra@arcor.de wrote:

Hi all!

I wonder what would be reasonable location accuracy if two cheap same type
GPS modules will be several meters apart? I understand that it involves
statistical numbers.

Any idea? Say for a small robot.

Thanks!

Henry

--
ehydra.dyndns.info

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--

Chris Albertson
Redondo Beach, California

I think the accuracy could be quite good if you took advantage of the times the robot was motionless. During those times it could build up many seconds of averaging and then while moving either use dead reckoning or inertial navigation. On Thu, Nov 24, 2011 at 4:01 AM, ehydra <ehydra@arcor.de> wrote: > Hi all! > > I wonder what would be reasonable location accuracy if two cheap same type > GPS modules will be several meters apart? I understand that it involves > statistical numbers. > > Any idea? Say for a small robot. > > Thanks! > - Henry > > > -- > ehydra.dyndns.info > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Chris Albertson Redondo Beach, California

AB

Azelio Boriani

Fri, Nov 25, 2011 12:57 PM

Yes, if you use statistics then you must be slow or, better, stop and
collect data. I think that ionosphere movements that cause errors are
slower than robots movements so it is hard to collect enough data for
statistics, of course maybe that only two points to average out is better
than nothing...

On Fri, Nov 25, 2011 at 7:43 AM, Chris Albertson
albertson.chris@gmail.comwrote:

I think the accuracy could be quite good if you took advantage of the
times the robot was motionless. During those times it could build up
many seconds of averaging and then while moving either use dead
reckoning or inertial navigation.

On Thu, Nov 24, 2011 at 4:01 AM, ehydra ehydra@arcor.de wrote:

Hi all!

I wonder what would be reasonable location accuracy if two cheap same

type

GPS modules will be several meters apart? I understand that it involves
statistical numbers.

Any idea? Say for a small robot.

Thanks!

Henry

--
ehydra.dyndns.info

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

--

Chris Albertson
Redondo Beach, California

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Yes, if you use statistics then you must be slow or, better, stop and collect data. I think that ionosphere movements that cause errors are slower than robots movements so it is hard to collect enough data for statistics, of course maybe that only two points to average out is better than nothing... On Fri, Nov 25, 2011 at 7:43 AM, Chris Albertson <albertson.chris@gmail.com>wrote: > I think the accuracy could be quite good if you took advantage of the > times the robot was motionless. During those times it could build up > many seconds of averaging and then while moving either use dead > reckoning or inertial navigation. > > On Thu, Nov 24, 2011 at 4:01 AM, ehydra <ehydra@arcor.de> wrote: > > Hi all! > > > > I wonder what would be reasonable location accuracy if two cheap same > type > > GPS modules will be several meters apart? I understand that it involves > > statistical numbers. > > > > Any idea? Say for a small robot. > > > > Thanks! > > - Henry > > > > > > -- > > ehydra.dyndns.info > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > > > -- > > Chris Albertson > Redondo Beach, California > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

PB

Pierpaolo Bernardi

Fri, Nov 25, 2011 1:57 PM

On Fri, Nov 25, 2011 at 06:26, ehydra ehydra@arcor.de wrote:

I read that for position accuracy ionospheric effects are the main source
for typical single frequency receivers. So looking for DOP would be not
helpful because the ionospheric way is for two 'relative' on the same
position located teceivers vs. satellites position almost the same and that
would cancel this error source out!? The end-effect should be better values
than seen in the datasheet.

Ionospheric effects account for about half the DOP, IIRC. So, if I understand
your requirement, and you are interested only in the relative
difference of position
between two nearby units, you should obtain a relative precision about double
of the absolute precision of a single unit.

If the units make use of WAAS or EGNOS, probably the gain in relative precision
would be less, I think.

If you do a test, let us know your findings.

Cheers
P.

On Fri, Nov 25, 2011 at 06:26, ehydra <ehydra@arcor.de> wrote: > I read that for position accuracy ionospheric effects are the main source > for typical single frequency receivers. So looking for DOP would be not > helpful because the ionospheric way is for two 'relative' on the same > position located teceivers vs. satellites position almost the same and that > would cancel this error source out!? The end-effect should be better values > than seen in the datasheet. Ionospheric effects account for about half the DOP, IIRC. So, if I understand your requirement, and you are interested only in the relative difference of position between two nearby units, you should obtain a relative precision about double of the absolute precision of a single unit. If the units make use of WAAS or EGNOS, probably the gain in relative precision would be less, I think. If you do a test, let us know your findings. Cheers P.

AK

Attila Kinali

Mon, Dec 5, 2011 8:09 PM

On Thu, 24 Nov 2011 13:01:41 +0100
ehydra ehydra@arcor.de wrote:

Hi all!

I wonder what would be reasonable location accuracy if two cheap same
type GPS modules will be several meters apart? I understand that it
involves statistical numbers.

Any idea? Say for a small robot.

On my endless quest to read the whole internet, i stumbled upon this:

http://gpspp.sakura.ne.jp/rtklib/rtklib.htm
http://gpspp.sakura.ne.jp/rtklib/rtklib_beagleboard.htm

I'm not 100% sure, but i think it looks like what you are looking for.

		Attila Kinali

--
Why does it take years to find the answers to
the questions one should have asked long ago?

On Thu, 24 Nov 2011 13:01:41 +0100 ehydra <ehydra@arcor.de> wrote: > Hi all! > > I wonder what would be reasonable location accuracy if two cheap same > type GPS modules will be several meters apart? I understand that it > involves statistical numbers. > > Any idea? Say for a small robot. On my endless quest to read the whole internet, i stumbled upon this: http://gpspp.sakura.ne.jp/rtklib/rtklib.htm http://gpspp.sakura.ne.jp/rtklib/rtklib_beagleboard.htm I'm not 100% sure, but i think it looks like what you are looking for. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago?

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