OpenCellID (was OpenBmap logger (GSM positioning)])
Thomas Landspurg
t.landspurg at 8motions.com
Sat Feb 21 10:46:12 CET 2009
2009/2/20 Nick <realtimeblog at gmail.com>
> Thomas,
>
> After trying to reach you a few times last year,
> i am really glad to have some news from you now.
>
The easiest way is to use the email mentionned in the Web page! ;-)
>
> I am reponsible for the openBmap website. And yes, it would be a great
> thing to merge our projects !
>
> The number of logs you have is very impressive ! well done !
>
> My concern would be about the quality of your data .
>
> you still mention on the front page
>
> "Note:If you want a professional CellID Database, I suggest you to go to
> Navizon
> who provides top services and databases."
>
> what do you mean ?
>
Tihs mean that there are company that have created huge databases of high
quality by spendig a lot of money on it, and they make money by selling
these data. Navizon pays his users for this, and other are throwing a lot of
money on this too, by sending people doing measures, or by buying operators
database. That's exactly the same difference between OpenStreetMap and
Navteq/Teleatlas. OpenStreetMap is free, provided by the community, but of a
lower quality than their commercial counterpart except on some specific area
not covered by these equivalents. Of course, the objective is to reach the
same quality, but this will take time.
>
> and after importing 800 000 of your gps points in january, I see that
> for instance
> gps speed, gps hdop, gps pdop, gps vdop are not available
> (at least at the begining of this huge measures.txt file !),
>
> A bad pdop, vdop, hdop and i am positioned at 1 km from my real position
> ...
> What if i am in a high speed train at 300 km/h? or in plane ? (yes, it
> can work in planes...)
>
Let's go back to the basics: the objective of these database if to provied
an positionning to create services using localisation on top of this
database. Let's take the sample of an high speed train: there is high
chances that all the sample will came from people in the train itself, and
not from the neighbour outside (train don't go at 300 km/h in high density
area). So this mean that the REAL position of the cell will never be
accuratly computed, which is not an issue, because the only interesting
information is the user position. So sampling mesures even some errors is
fine as long as it works fine to get user position.
So the philosophy behing opencellid was to reach the 80/20 ratio:
acheiving the 80% of functionality will require only 20% of the time needed
to do these 100% functionality. So that's why we have a simple and elegant
API, that is used by different devices with different capacities, while
acheiving exactly this objective: providing an accurate cell id
positionning.
>
>
> In my opinion, considering the following services
>
> *** asisted gps
> *** "cell id" to google "my position" kind of service
> *** "cell id" to "town name" service
>
> the real questions are:
> what precision do we need for openmoko location service through gsm cell
> id ?
> what precision our possibly merged database would provide ?
>
>
Assisted GPS does not require huge precision. I am not an expert, but I
would be curious to know what is the precision needed to get an assisted
GPS. Using triangulation is a different story, and this obvisouly will work
fine only in high density area, where you also have high density cells. So
again, there is a direct correlation between the precision and the density
of the area.
Note also that OpenCellID use LAC (Local Area Code) to provide an
alternate positioning with a lower precision if a cell is not know, but if
the LAC is know. Typically other cells has been discovered in the same area.
So once you get CellID positionning, you can use reverse geocoding
service to get the town for instance.
> what do you think about the above considerations ?
>
> really glad to hear from you !
>
> regards,
> Nick
>
> Thomas Landspurg a écrit :
> >
> >
> > 2009/2/20 Onen <onen.om <http://onen.om>@free.fr <http://free.fr>>
> >
> > Hi Thomas,
> >
> > Thomas Landspurg wrote:
> > >
> > > Dear OpenMoko community (and thanks ed for pointing this out).
> > >
> > > I am behind the opencellid.org <http://opencellid.org>
> > <http://opencellid.org> project, and it
> > > seems that there are some discussion around it these day on the
> > mailing
> > > list.
> > >
> >
> > Last month, and today, indeed.
> >
> >
> > Yes, I've get to it today! It's a pity not to have been notified of
> > such discussion before. I've been through them, and I want to add some
> > clarification about difference between database:
> >
> > - OpenCellID can also store signal strengh. But one of the issue, is
> > heterogenity between datas. Some client don't have this information,
> > and this create some additional complexity. That's why this
> > information is for now only stored but not yet used. And in all was,
> > if you want it, it's in the measure table, and not in the cell table.
> >
> > - About the barycenter of the area/instead of barycenter: it's not
> > always the best way to do it, as it give more value to false datas.
> > while the "simple" barycenter reduce these. Another option would be to
> > exclude data that would be completely "out of range"
> >
> > And more "general" information about the databse: more than 500
> > developers have registered to get an API key. Obvisouly not 500
> > application are out, but show the interest of the community
> >
> >
> >
> >
> > > So let me clarifiy:
> > >
> > > - As described in the web site, the license is under creative
> common
> > > share alike 3.0. I had several request today stating that just
> > linking
> > > to the license was not clear enough, so I will re-clarify it on
> > the web
> > > site, but also in this list.
> > >
> >
> > Last time I checked (and other people, see the post I pointed out
> > earlier today), it was not clear. But today, as people had a look
> > again,
> > it seems to me pretty clear :-)
> >
> >
> > Last time, it was written under creative common license, with a link
> > to the creative common share alike license. I am sorry if this was not
> > clear enough, but as you see, a simple mail is enough to get it
> corrected.
> >
> >
> >
> >
> > > - I am surprised to see statment that I did not answer to some
> > > questions. I've verified,and all openmoko request have been
> > answered. I
> > > am not perfect, and may be some emails have been missed, but a
> > search on
> > > openmoko on my mail box did not raise any pending question.
> > >
> >
> > Not sure what you mean by openmoko request... When I stated that
> > neither
> > us nor openmoko did get an answer, I should have written: "If I
> recall
> > correclty openmoko tried to reach opencellid, but I have not heard of
> > any response. We tried to contact opencellid, but got no response." I
> > personally have not tried to reach you. But Nick yes, without answer,
> > for what I have understood.
> >
> >
> > Would be curious to have his email just to check. I am quite sure
> > I've answered to all demands like this.
> >
> >
> > > There is more than 100 000 cells covered, with 5.5 millions of
> > > measure, and more cells will be "donated" soon. We expect to
> > reach 200
> > > 000 cells in the coming weeks thanks to a new project donation.
> > There is
> > > also more than 10 different clients (windows mobile, symbian,
> > > blackberry, j2me,...) gathering the database.
> > >
> >
> > Is there different countries?
> >
> >
> > Yes, the stats page show all countries:
> >
> > http://www.opencellid.org/cell/stats
> >
> >
> >
> > Good to see there is no client for openmoko, otherwise I may have
> > worked
> > for nothing ;-)
> >
> >
> > Yes, I've heard that other where working on such client too!
> >
> >
> >
> > > I've been running this project since more than one year , with an
> > > objective to push community efforts around cell id. So I would
> > be more
> > > than happy to see new effort joining this project instead of
> > creating
> > > separate efforts. So let's join effort and create something big!
> > >
> >
> > I am very glad to read this, especially as I was very disappointed
> not
> > being able to leverage the existing work you have done. For my part I
> > work on the client side. A logger/uploader. I guess it would be
> > easy to
> > modify it to upload to your database if we go that way. But for now,
> I
> > think it would be good Nick (who takes care of the server side)
> > and you
> > keep discussing, in order to evaluate a possible merger.
> >
> > As there are also plans on embedding the database on the phone, and
> > using it to locate, I would like to know if this part would interest
> > you? Or only the server side and upload?
> >
> >
> > The idea is to provide all the means to do so. So if there is anything
> > that is needed to help you to do this, I would be happy to provide it.
> > For instance, a way to send an area and get the list of cells in that
> > area. I amalready working on such functionality.
> > But the switch to from OpenBMap to OpenCellID should be quite fast
> > as I assume that the API is probably the same, or very close to. (
> > http://www.opencellid.org/api )
> >
> >
> >
> > > And as a reminder, the complete data base is available for
> > download.
> > >
> > > So if you have any question/interrogation, feel free to share
> > them with
> > > me so we can clarify this.
> > >
> > > Regards,
> >
> > Great we can move along. I hated this feeling of reinventing the
> > wheel!
> >
> >
> > So do I!
> >
> >
> >
> > Onen
> >
> >
> > _______________________________________________
> > Openmoko community mailing list
> > community at lists.openmoko.org <mailto:community at lists.openmoko.org>
> > http://lists.openmoko.org/mailman/listinfo/community
> >
> >
> >
> >
> > --
> > Thomas LANDSPURG
> > 8Motions
> > Founder/CTO
> > http://www.8motions.com
> > http://www.opencellid.org
> >
> >
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > Openmoko community mailing list
> > community at lists.openmoko.org
> > http://lists.openmoko.org/mailman/listinfo/community
> >
>
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>
--
Thomas LANDSPURG
8Motions
Founder/CTO
http://www.8motions.com
http://www.opencellid.org
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