Re: thoughts on A-GPS offline

2009-03-18 Thread Helge Hafting
Daniel Willmann wrote:
 On Tue, 10 Mar 2009 15:18:23 +0100
 Helge Hafting helge.haft...@hist.no wrote:
[...]
 It was just to be safe. The documentation states that you might not
 get a fix _at all_ if either position or time is outside the claimed 
 accuracy. Now, maybe it works with 3km anyway after the fixes that 
 prevents the chip-crashing exception. I happen to live about 6km away 
 from where I work, so 9km was a nice safe value. The default is
 300km, and 100km allows a more optimistic startup. Perhaps such
 rough estimates is all that is needed, if it is only used to figure
 which satellites that can be seen.
 
 If you don't mind testing please try changing pacc to 100km and see if
 it affects TTFF adversely in your case. If not we could just use that
 as a default.

Shouldn't be too hard to test.

I think I know one side of having accurate pacc:

The first fix can happen with only two satellites. I have seen this 
happen several times. It surprised me at first, but it makes sense. With 
two satellites (and a reasonable clock), you get a big circle of 
possible positions. But then there is the data from the approximate 
position. It puts you at some height above sea level. The big circle 
intersects the earth surface at some angle, so with height, we now have 
two possible spots instead of a big circle. Usually, only one spot will 
be close to the approximate position, so that is where you are.

That is an optimistic startup scenario. A too spread out pacc means 
both possible spots are within pacc range, and the FR will have to wait 
for a third satellite to break the tie.

If you travel a long way and still report the old position with a fake 
precision pacc, then you might be close to the other of the two possible 
satellite-based positions. You could then get a fake fix on the wrong 
spot. As you and/or the satellites move, the wrong spot will move around 
in strange ways at strange speeds. When more satellites show up, the 
device might get really confused if it keeps trusting the approximate 
position. Perhaps even rejecting them as reflected signals for a 
while. Of course, only the manufacturer will know the exact details of 
what might happen.

Helge Hafting









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Re: thoughts on A-GPS offline

2009-03-18 Thread Joerg Reisenweber
Am Mi  18. März 2009 schrieb Helge Hafting:
 Daniel Willmann wrote:
  On Tue, 10 Mar 2009 15:18:23 +0100
  Helge Hafting helge.haft...@hist.no wrote:
 [...]
  It was just to be safe. The documentation states that you might not
  get a fix _at all_ if either position or time is outside the claimed 
  accuracy. Now, maybe it works with 3km anyway after the fixes that 
  prevents the chip-crashing exception. I happen to live about 6km away 
  from where I work, so 9km was a nice safe value. The default is
  300km, and 100km allows a more optimistic startup. Perhaps such
  rough estimates is all that is needed, if it is only used to figure
  which satellites that can be seen.
  
  If you don't mind testing please try changing pacc to 100km and see if
  it affects TTFF adversely in your case. If not we could just use that
  as a default.
 
 Shouldn't be too hard to test.
 
 I think I know one side of having accurate pacc:
 
 The first fix can happen with only two satellites. I have seen this 
 happen several times. It surprised me at first, but it makes sense. With 
 two satellites (and a reasonable clock), you get a big circle of 
 possible positions. But then there is the data from the approximate 
 position. It puts you at some height above sea level. The big circle 
 intersects the earth surface at some angle, so with height, we now have 
 two possible spots instead of a big circle. Usually, only one spot will 
 be close to the approximate position, so that is where you are.
 
 That is an optimistic startup scenario. A too spread out pacc means 
 both possible spots are within pacc range, and the FR will have to wait 
 for a third satellite to break the tie.
 
 If you travel a long way and still report the old position with a fake 
 precision pacc, then you might be close to the other of the two possible 
 satellite-based positions. You could then get a fake fix on the wrong 
 spot. As you and/or the satellites move, the wrong spot will move around 
 in strange ways at strange speeds. When more satellites show up, the 
 device might get really confused if it keeps trusting the approximate 
 position. Perhaps even rejecting them as reflected signals for a 
 while. Of course, only the manufacturer will know the exact details of 
 what might happen.
 
 Helge Hafting

Wow, I had to read your posting twice to get how brilliant this analysis is.

cheers
jOERG


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Re: thoughts on A-GPS offline

2009-03-11 Thread Daniel Willmann
On Tue, 10 Mar 2009 15:18:23 +0100
Helge Hafting helge.haft...@hist.no wrote:

 I do not get 7s every time. This was an ideal test, I was standing in
 a place with good visibility. the gps used 9 or so satellites. Then I 
 stopped tangogps and restarted it, and timed it from the moment the 
 tangogps screen showed. (So as to not include the startup time for 
 tangogps itself). The TTFF is usually a little longer inside a bus or 
 building.

Okay, this still sounds really promising and matches my experience.
Even when riding my bike I now usually get a fix within the first
minute, mostly within 30 seconds. Before uploading ephemeris this often
took several minutes (sometimes it wouldn't get a fix until I stood
still for 20 seconds even after riding around for ~10 minutes).

  so the chip knows which SVs to search for. So a pacc of 3km or 9km
  shouldn't have any noticable effect. This is just guesswork though,
  so any results on your part would be greatly appreciated.
 
 It was just to be safe. The documentation states that you might not
 get a fix _at all_ if either position or time is outside the claimed 
 accuracy. Now, maybe it works with 3km anyway after the fixes that 
 prevents the chip-crashing exception. I happen to live about 6km away 
 from where I work, so 9km was a nice safe value. The default is
 300km, and 100km allows a more optimistic startup. Perhaps such
 rough estimates is all that is needed, if it is only used to figure
 which satellites that can be seen.

If you don't mind testing please try changing pacc to 100km and see if
it affects TTFF adversely in your case. If not we could just use that
as a default.


Regards,
Daniel Willmann


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Re: thoughts on A-GPS offline

2009-03-10 Thread Helge Hafting
Daniel Willmann wrote:
 On Wed, 04 Mar 2009 13:59:07 +0100
 Helge Hafting helge.haft...@hist.no wrote:
 
 Thanks a lot!
 I needed this one too, and now get 7s warm starts!
 http://git.freesmartphone.org/?p=framework.git;a=commitdiff;h=ad2ec48cdb5ab9bdddc15adfc05cbd2e5b8a2cee
 
 7s TTFF is pretty good. I got that once, but usually I have about 16s
 TTFF.
 
I do not get 7s every time. This was an ideal test, I was standing in a 
place with good visibility. the gps used 9 or so satellites. Then I 
stopped tangogps and restarted it, and timed it from the moment the 
tangogps screen showed. (So as to not include the startup time for 
tangogps itself). The TTFF is usually a little longer inside a bus or 
building.

 I also raised pacc from 3km to 9km, as I often enough travel a bit
 more than 3km with the gps unit off.
 
 I'm interested to hear how that affects TTFF. The way I understand it
 initial position is only used to calculate which SVs are in view so the
 chip knows which SVs to search for. So a pacc of 3km or 9km shouldn't
 have any noticable effect. This is just guesswork though, so any
 results on your part would be greatly appreciated.

It was just to be safe. The documentation states that you might not get 
a fix _at all_ if either position or time is outside the claimed 
accuracy. Now, maybe it works with 3km anyway after the fixes that 
prevents the chip-crashing exception. I happen to live about 6km away 
from where I work, so 9km was a nice safe value. The default is 300km, 
and 100km allows a more optimistic startup. Perhaps such rough 
estimates is all that is needed, if it is only used to figure which 
satellites that can be seen.

Helge Hafting







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Re: thoughts on A-GPS offline

2009-03-09 Thread mqy

I'm not using ogpsd. The parser is written by I myself.
My strategy is to filter out dumped ALM/EPH messages which contain
zeros after SV id in payload.
Need more tests to verify this can avoid chip crash :)

2009/3/9 Daniel Willmann (via Nabble) ml-user+51571-985684...@n2.nabble.com:
 On Tue, 3 Mar 2009 06:47:26 -0800 (PST)
 mqy meng.qing...@... wrote:


 I've verified the issue on GPS receiver in GTA02:

 When dump ALM/EPH messages, in several messages, fields follow SV ID
 field in payload are filled with zeros.

 Okay, so what you're saying is that this commit
 http://git.freesmartphone.org/?p=framework.git;a=commitdiff;h=ad2ec48cdb5ab9bdddc15adfc05cbd2e5b8a2cee
 doesn't fix the situation for you?
 If that is the case could you please send me the ALM/EPH messages that
 you get when the chip crashes so I can take a look at it?

 Regards,
 Daniel Willmann


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Re: thoughts on A-GPS offline

2009-03-08 Thread Daniel Willmann
On Tue, 3 Mar 2009 06:47:26 -0800 (PST)
mqy meng.qing...@gmail.com wrote:

 
 I've verified the issue on GPS receiver in GTA02:
 
 When dump ALM/EPH messages, in several messages, fields follow SV ID
 field in payload are filled with zeros.

Okay, so what you're saying is that this commit
http://git.freesmartphone.org/?p=framework.git;a=commitdiff;h=ad2ec48cdb5ab9bdddc15adfc05cbd2e5b8a2cee
doesn't fix the situation for you?
If that is the case could you please send me the ALM/EPH messages that
you get when the chip crashes so I can take a look at it?

Regards,
Daniel Willmann


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Re: thoughts on A-GPS offline

2009-03-04 Thread Helge Hafting
Stefan Schmidt wrote:
 Hello.
 
 On Tue, 2009-03-03 at 12:31, Helge Hafting wrote:
 Daniel Willmann wrote:

 Now that hot-/warmstart with ephemeris playback works with the framework
 we should try to get an open server with aiding data available ASAP.

 I hope that fso-gpsd gets updated soon too
 
 Already done:
 http://git.freesmartphone.org/?p=framework.git;a=commitdiff;h=5271e445b327c2132eee6a1f43fcf58c37c67e00
 http://git.freesmartphone.org/?p=framework.git;a=commitdiff;h=0838645958d50df38e64429a27672570bf58f8b4

Thanks a lot!
I needed this one too, and now get 7s warm starts!
http://git.freesmartphone.org/?p=framework.git;a=commitdiff;h=ad2ec48cdb5ab9bdddc15adfc05cbd2e5b8a2cee

I also raised pacc from 3km to 9km, as I often enough travel a bit more 
than 3km with the gps unit off.

Helge Hafting

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Re: thoughts on A-GPS offline

2009-03-03 Thread Daniel Willmann
On Tue, 03 Mar 2009 12:31:00 +0100
Helge Hafting helge.haft...@hist.no wrote:

 Daniel Willmann wrote:
 
  Now that hot-/warmstart with ephemeris playback works with the
  framework we should try to get an open server with aiding data
  available ASAP.
  
 I hope that fso-gpsd gets updated soon too - it'd sure be nice to
 take advantage of a recently saved ephemeris when restarting gps
 software.

fso-gpsd doesn't need to get updated, it just uses ogpsd which is
saving/restoring the ephemeris received from the SVs already.
For the improved ogpsd you will need a recent version of frameworkd as
Stefan has already pointed out.

Regards,
Daniel Willmann


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Re: thoughts on A-GPS offline

2009-03-03 Thread mqy

I've verified the issue on GPS receiver in GTA02:

When dump ALM/EPH messages, in several messages, fields follow SV ID field
in payload are filled with zeros.


Daniel Willmann wrote:
 
 On Sun, 1 Mar 2009 14:25:14 -0800 (PST)
 mqy meng.qing...@gmail.com wrote:
 
 
 UBX-AID-EPH and UBX-AID-ALM Messages for Satellite without valid
 Orbits When polling UBX-AID-EPH or UBX-AID-ALM messages, satellites
 without valid ephemeris or almanac data will 
 return a complete UBX-AID-EPH or UBX-AID-ALM message with all data
 words set to zero. This doesn’t comply 
 with the protocol specification. Furthermore, u-blox 5 receivers with
 firmware V5.00 and earlier can run into a 
 floating-point exception when fed with such “empty” ephemeris. 
 
 
 Is that the cause :D
 
 Yeah, thought that at first as well, but almanac data was okay at that
 point. The position was not, however. I guess the problem the chip
 tripped over is similar in both cases though.
 
 Regards,
 Daniel Willmann
 
  
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Re: thoughts on A-GPS offline

2009-03-02 Thread Daniel Willmann
On Sun, 1 Mar 2009 14:25:14 -0800 (PST)
mqy meng.qing...@gmail.com wrote:

 
 UBX-AID-EPH and UBX-AID-ALM Messages for Satellite without valid
 Orbits When polling UBX-AID-EPH or UBX-AID-ALM messages, satellites
 without valid ephemeris or almanac data will 
 return a complete UBX-AID-EPH or UBX-AID-ALM message with all data
 words set to zero. This doesn’t comply 
 with the protocol specification. Furthermore, u-blox 5 receivers with
 firmware V5.00 and earlier can run into a 
 floating-point exception when fed with such “empty” ephemeris. 
 
 
 Is that the cause :D

Yeah, thought that at first as well, but almanac data was okay at that
point. The position was not, however. I guess the problem the chip
tripped over is similar in both cases though.

Regards,
Daniel Willmann


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Re: thoughts on A-GPS offline

2009-03-01 Thread Raphaël Jacquot
On Sun, Mar 01, 2009 at 08:31:16PM +0100, Daniel Willmann wrote:
 Now that hot-/warmstart with ephemeris playback works with the framework
 we should try to get an open server with aiding data available ASAP.

is there a way to get the ephemeris data from the gps receiver at some point ?
it could be stored on the phone and used as a calculation aide...

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Re: thoughts on A-GPS offline

2009-03-01 Thread mqy

U-blox receiver allows polling AID-EPH, AID-ALM data.
For each type, we can poll 32 messages for 32 satellites. 
The precondition is: current fix is valid -- at least 3 SVs has valid EPH(or
ALM?) data.

These data get invalid 2~4 hours later, 
can be stored into files, and load into GPS receiver when needed and they
are valid.

I've tried this, not sure whether it works or not, need more tests:)
AGPS-online works fine.


Raphaël Jacquot wrote:
 
 On Sun, Mar 01, 2009 at 08:31:16PM +0100, Daniel Willmann wrote:
 Now that hot-/warmstart with ephemeris playback works with the framework
 we should try to get an open server with aiding data available ASAP.
 
 is there a way to get the ephemeris data from the gps receiver at some
 point ?
 it could be stored on the phone and used as a calculation aide...
 
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Re: thoughts on A-GPS offline

2009-03-01 Thread Raphaël Jacquot
On Sun, Mar 01, 2009 at 12:57:30PM -0800, mqy wrote:
 
 U-blox receiver allows polling AID-EPH, AID-ALM data.
 For each type, we can poll 32 messages for 32 satellites. 
 The precondition is: current fix is valid -- at least 3 SVs has valid EPH(or
 ALM?) data.
 
 These data get invalid 2~4 hours later, 
 can be stored into files, and load into GPS receiver when needed and they
 are valid.

they can probably still be used to get a rough estimate

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Re: thoughts on A-GPS offline

2009-03-01 Thread Daniel Willmann
On Sun, 1 Mar 2009 21:39:25 +0100
Raphaël Jacquot sxp...@sxpert.org wrote:

 On Sun, Mar 01, 2009 at 08:31:16PM +0100, Daniel Willmann wrote:
  Now that hot-/warmstart with ephemeris playback works with the
  framework we should try to get an open server with aiding data
  available ASAP.
 
 is there a way to get the ephemeris data from the gps receiver at
 some point ? it could be stored on the phone and used as a
 calculation aide...

Yes and that's what ogpsd does already. It has been saving/restoring
almanac for months, ephemeris was disabled up until recently because
there was a bug that prevented the GPS chip from doing anything useful
after they were restored to the chip.

The chip will use all available data to calculate the fix. With
restoring ephemeris this means a time to first fix of about 16 seconds
at the moment. Not sure how much faster we can get.

Regards,
Daniel Willmann


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Re: thoughts on A-GPS offline

2009-03-01 Thread mqy

From [
http://www.u-blox.cn/customersupport/gps.g5/ublox5_Fw5.00_Release_Notes(GPS.G5-SW-08019).pdf
]:


UBX-AID-EPH and UBX-AID-ALM Messages for Satellite without valid Orbits
When polling UBX-AID-EPH or UBX-AID-ALM messages, satellites without valid
ephemeris or almanac data will 
return a complete UBX-AID-EPH or UBX-AID-ALM message with all data words set
to zero. This doesn’t comply 
with the protocol specification. Furthermore, u-blox 5 receivers with
firmware V5.00 and earlier can run into a 
floating-point exception when fed with such “empty” ephemeris. 


Is that the cause :D


Daniel Willmann wrote:
 
 
 Yes and that's what ogpsd does already. It has been saving/restoring
 almanac for months, ephemeris was disabled up until recently because
 there was a bug that prevented the GPS chip from doing anything useful
 after they were restored to the chip.
 
 ... ...
 
 Regards,
 Daniel Willmann
 
  
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Re: thoughts on A-GPS offline

2009-02-22 Thread Helge Hafting



Timo Juhani Lindfors wrote:
 
 
 It is already possible to set up a free server for almanac data, as 
 saving and loading almanac data works well and speed up TTFF some.
 
 But where do we get this almanac data? Can we redistribute what
 u-box.com sends us?
 

Almanac data is valid for a couple of months, so normally you use the
almanac that was auto-saved last time you used your gps.

If someone set up a free server, then we can also upload almanac data there,
and download it to speed up TTFF in cases where the gps hasn't been used for
2 months (or a newly flashed image overwrote the locally saved almanac).

Of course, a locally saved almanac will usually do the trick, so such a
service becomes more interesting when the epheremis can be saved as well.
(once the bugs in ephemeris uploading gets fixed - currently this can fail
rather badly, yielding no fix at all) Ephemeris data is only valid for 30min
or so. Saving the ephemeris locally helps if your gps app crash and gets
restarted, but it won't help you the following day. A server could help
though.


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Re: thoughts on A-GPS offline

2009-02-22 Thread mqy

Yes, ogpsd within frameworkd saves/loads u-blox AID HUI/ALM/EPH messages.
u-blox A-GPS online messages are of AID message types. Let's read the html
content dumped from ghex:



 b5 62 0b 01 30 00 2d 26 29 f3 ba ca 13 1a ec b7 6b 18 20 a1 07 00 00 00 ee
 05 c4 7a 67 0e 00 00
 
 00 00 f4 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 00 00 00 e8 ce b5
 62 0b 31 68 00 03 00
 
 00 00 80 59 4d 00 00 91 7b 00 51 1b 68 00 06 8a 7e 00 cd 3c 55 00 f7 fb b4
 ff c4 3b 3c 00 2e 00
 
 00 00 3b 09 2e 00 d9 fc 3c 00 0e 2e 37 00 9c 27 f2 ff 05 3d fd ff bc 6c f6
 ff a1 db 1c 00 8f f7
 
 0d 00 7f c4 3b 00 0d c9 ff ff 33 17 41 00 25 59 00 00 22 32 c1 ff 24 44 0c
 00 e5 50 46 00 16 a4
 
 ff ff 33 06 3c 00 e2 f7 b5 62 0b 31 68 00 06 00 00 00 80 59 4d 00 00 90 7b
 00 51 1b 60 00 06 8a
 
 7e 00 cd 3c 55 00 f6 fb b4 ff c4 3b 20 00 82 ff 00 00 10 12 08 00 0b fe 20
 00 75 5d 34 00 c2 12
 
 ae ff 02 fb fd ff 4e 22 ec ff a1 0e 1d 00 79 ca 0d 00 7c c4 3b 00 0f 3c 00
 00 d4 c1 f8 ff 26 f8
 
 ff ff dc 30 0f 00 c4 df 0b 00 e7 c0 95 ff 0c a8 ff ff 3b 0b 20 00 2b 9d b5
 62 0b 31 68 00 19 00
 
 00 00 80 59 4d 00 00 92 7b 00 51 1b 70 00 06 8a 7e 00 cd 3c 55 00 f0 fb b4
 ff c4 3b 6b 00 db 00
 
 00 00 1f a6 1e 00 ff 0c 6b 00 8a bb 31 00 cc bd ea ff 06 1a 0b 00 88 76 0a
 00 a1 9b 07 00 27 59
 
 0d 00 7f c4 3b 00 b8 39 00 00 22 17 98 ff 27 12 00 00 c8 d0 70 00 cd 13 27
 00 b7 86 fa ff 77 a6
 
 ff ff eb 11 6b 00 9e ee b5 62 0b 31 68 00 13 00 00 00 00 f1 4d 00 00 90 7b
 00 51 1b 60 00 06 8a
 
 7e 00 cd 3c 55 00 e1 fb b4 ff c3 3b 0c 00 fb ff 00 00 46 46 04 00 57 00 0c
 00 29 41 2f 00 48 c4
 
 d7 ff 02 49 00 00 75 0b a2 ff a1 b9 1c 00 3a 5d 0e 00 1c c3 3b 00 14 3d 00
 00 cb 85 b9 ff 27 17
 
 00 00 68 fa 05 00 f0 fa 0d 00 07 56 28 00 c0 a9 ff ff 59 10 0c 00 30 ab b5
 62 0b 31 68 00 0d 00
 
 00 00 80 59 4d 00 00 90 7b 00 51 1b 60 00 06 8a 7e 00 cd 3c 55 00 e8 fb b4
 ff c4 3b 29 00 0b 00
 
 00 00 c8 c3 25 00 b1 09 29 00 39 9f 24 00 00 9d 3e 00 01 0f 08 00 65 c0 ed
 ff a1 85 1d 00 a4 18
 
 0e 00 7c c4 3b 00 94 e8 ff ff d3 5b 00 00 28 d7 ff ff 20 85 8f ff 3d 86 0f
 00 60 1c 5a 00 25 ae
 
 ff ff 94 01 29 00 0d b3 b5 62 0b 31 68 00 10 00 00 00 80 59 4d 00 00 90 7b
 00 51 1b 60 00 06 8a
 
 7e 00 cd 3c 55 00 eb fb b4 ff c4 3b 1d 00 e7 ff 00 00 cd e8 09 00 9d f1 1d
 00 74 3a 31 00 84 6b
 
 89 ff 02 a4 f3 ff 15 cc 98 ff a1 fa 0c 00 94 1a 0e 00 63 c4 3b 00 e7 d7 ff
 ff 4a a6 fe ff 27 3a
 
 00 00 19 e8 6d 00 f0 d2 20 00 cc 99 42 00 53 a6 ff ff 6f ee 1d 00 be a9 b5
 62 0b 31 68 00 17 00
 
 00 00 80 59 4d 00 00 91 7b 00 51 1b 68 00 06 8a 7e 00 cd 3c 55 00 d5 fb b4
 ff c4 3b 66 00 06 00
 
 00 00 ec b1 32 00 a2 08 66 00 14 e9 2a 00 af 4b 56 00 02 2f 07 00 b4 41 f6
 ff a1 a1 1c 00 0f 39
 
 0d 00 7d c4 3b 00 91 31 00 00 68 58 fc ff 27 f3 ff ff e4 48 91 ff 75 ca 0e
 00 3b 50 5e 00 a1 aa
 
 ff ff 32 fe 66 00 28 bd b5 62 0b 31 68 00 07 00 00 00 80 59 4d 00 00 90 7b
 00 51 1b 60 00 06 8a
 
 7e 00 cd 3c 55 00 e9 fb b4 ff c4 3b 1b 00 fd ff 00 00 ca fb 02 00 04 0a 1b
 00 d3 73 33 00 ad 74
 
 71 00 01 79 08 00 ac 04 2e 00 a1 5e 06 00 05 64 0d 00 45 c4 3b 00 bc df ff
 ff 5a 61 74 00 27 c0
 
 ff ff 7f 27 58 00 77 90 28 00 53 f6 32 00 7c a3 ff ff 10 10 1b 00 88 4b b5
 62 0b 31 68 00 15 00
 
 00 00 80 59 4d 00 00 90 7b 00 51 1b 60 00 06 8a 7e 00 cd 3c 55 00 e7 fb b4
 ff c4 3b 5f 00 f0 ff
 
 00 00 9a e3 03 00 51 06 5f 00 ad bd 3d 00 0f b8 df ff 07 f8 04 00 91 5c 7e
 00 a1 03 09 00 4a 19
 
 0d 00 7c c4 3b 00 3d 55 00 00 e3 4e 49 00 26 b8 ff ff 62 b9 0f 00 94 48 23
 00 70 fd 28 00 9d a1
 
 ff ff 27 18 5f 00 0c b6 b5 62 0b 30 28 00 19 00 00 00 ee 05 00 00 9f 60 59
 00 b3 10 63 00 00 48
 
 fd ff f7 0c a1 ff 64 8a b8 ff b0 01 ce ff 80 ec 45 00 e5 00 1f 00 ac f0 b5
 62 0b 30 28 00 13 00
 
 00 00 ee 05 00 00 32 2a 53 00 f9 09 63 00 00 5c fd ff f1 0d a1 ff 4b ac 14
 00 7d 23 f0 ff 37 ec
 
 
.

Each individual message format is:
1. head: b5 62; 
2. the message class/id, e.g. 0b 01, 0b 30, 0b 31;
3. 2 bytes content length;
4. message content;
5. 2 bytes checksum.

There is no message head in offline data file from u-blox (e.g,
http://alp.u-blox.com/current_1d.alp),
this prevents us from extracting (and/or calculate) AID data then load into
u-blox GPS receiver.
As of HUI/ALM/EPH, ANTARIS_Protocol_Specification(GPS.G3-X-03002).chm says:
See ICD-GPS-200 for a full description of the contents of...
Sigh, If freerunner has flash memory, the offline data can be directly
submitted to u-blox GPS receiver. 



Helge Hafting wrote:
 
 Cédric Berger wrote:
 On Wed, Feb 18, 2009 at 17:49, Al Johnson openm...@mazikeen.demon.co.uk
 wrote:
 I may be misunderstanding the suggestion, but I don't think it had
 anything to
 do with data from ublox. The suggestion was to use data sent by other
 freerunner users instead of the data supplied by ublox.
 
 As I understood the suggestion was in reply to :
 
 It is not a problem that user account is required when download u-blox
 online
 aiding data.
 It is a problem since u-blox might go out of business and you might
 not want to tell them where you are all 

Re: thoughts on A-GPS offline

2009-02-20 Thread Helge Hafting
Cédric Berger wrote:
 On Wed, Feb 18, 2009 at 17:49, Al Johnson openm...@mazikeen.demon.co.uk 
 wrote:
 I may be misunderstanding the suggestion, but I don't think it had anything 
 to
 do with data from ublox. The suggestion was to use data sent by other
 freerunner users instead of the data supplied by ublox.
 
 As I understood the suggestion was in reply to :
 
 It is not a problem that user account is required when download u-blox 
 online
 aiding data.
 It is a problem since u-blox might go out of business and you might
 not want to tell them where you are all time. Their server also might
 be down. There are plenty of reasons to remove dependency to any
 single party.
 
 The problem is that data from u-blox is a proprietary format, and as
 far as I know, we do not know yet how to create the same data that can
 be pushed to the GPS chip.

As far as I know - we do know the format. The SHR distribution
already saves such data before turning the gps off, and restores it when 
you turn it on so you get the first fix quicker.

Not all the data is used at the moment, because the process sometimes 
fail yelding long startup times. But that should only be a debugging 
problem.

It is already possible to set up a free server for almanac data, as 
saving and loading almanac data works well and speed up TTFF some.

Helge Hafting

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Re: thoughts on A-GPS offline

2009-02-20 Thread Timo Juhani Lindfors
Helge Hafting helge.haft...@hist.no writes:
 As far as I know - we do know the format. The SHR distribution

Yes frameworkd ogpsd has some info about it:

# Feed GPS with position and time
self.send(AID-INI, 48, {X : pos.get(x, 0) , Y : pos.get(y, 0) , Z : 
pos.get(z, 0), \
  POSACC : pacc, TM_CFG : 0 , WN : wn , TOW : tow , TOW_NS : 
0 , \
  TACC_MS : tacc , TACC_NS : 0 , CLKD : 0 , CLKDACC : 0 , 
FLAGS : flags })


# Feed gps with almanac
if self.aidingData.get( almanac, None ):
for k, a in self.aidingData[almanac].iteritems():
logger.debug(Loaded almanac for SV %d % a[SVID])
self.send(AID-ALM, 40, a);

Good to know that the hope is not lost! :-)

 It is already possible to set up a free server for almanac data, as 
 saving and loading almanac data works well and speed up TTFF some.

But where do we get this almanac data? Can we redistribute what
u-box.com sends us?



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Re: thoughts on A-GPS offline

2009-02-20 Thread Stefan Monnier
 But where do we get this almanac data? Can we redistribute what
 u-box.com sends us?

AFAIK, the almanac data that framworkd saves from the GPS can come from
u-blox but can also come directly from the GPS satellites.  So we could
try to setup some kind of peer-to-peer distribution of the data
downloaded from the satellites.  Of course, that presumes we have the
right to distribute the satellite's data.


Stefan




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Re: thoughts on A-GPS offline

2009-02-18 Thread Helge Hafting
Timo Juhani Lindfors wrote:
 mqy meng.qing...@gmail.com writes:
 It is not a problem that user account is required when download u-blox online
 aiding data.
 
 It is a problem since u-blox might go out of business and you might
 not want to tell them where you are all time. Their server also might
 be down. There are plenty of reasons to remove dependency to any
 single party.

It is possible to start an open service, with mirrors. Interested people 
can set their freerunners to send in good aiding data when they have it 
(i.e. when using the gps and a network is available.)

Such a update gives away where you are, because the satellite 
constellation is only seen from part of the world. But I believe this 
part is large enough for privacy.

People using the service don't need to give away much. In an extreme 
case they will download ephemeris data for _all_ satellites, and then do 
the processing based on approximate location in the phone itself.


Helge Hafting

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Re: thoughts on A-GPS offline

2009-02-18 Thread Cédric Berger
On Wed, Feb 18, 2009 at 16:52, Helge Hafting helge.haft...@hist.no wrote:
 Timo Juhani Lindfors wrote:
 mqy meng.qing...@gmail.com writes:
 It is not a problem that user account is required when download u-blox 
 online
 aiding data.

 It is a problem since u-blox might go out of business and you might
 not want to tell them where you are all time. Their server also might
 be down. There are plenty of reasons to remove dependency to any
 single party.

 It is possible to start an open service, with mirrors. Interested people
 can set their freerunners to send in good aiding data when they have it
 (i.e. when using the gps and a network is available.)


Infos downloaded from u-blox are only valid for some time. So if
server is down for more than just a short time, it won't help much.
And I did not check but not I am not sure u-blox terms of service
allow to redistribute...

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Re: thoughts on A-GPS offline

2009-02-18 Thread Al Johnson
On Wednesday 18 February 2009, Cédric Berger wrote:
 On Wed, Feb 18, 2009 at 16:52, Helge Hafting helge.haft...@hist.no wrote:
  Timo Juhani Lindfors wrote:
  mqy meng.qing...@gmail.com writes:
  It is not a problem that user account is required when download u-blox
  online aiding data.
 
  It is a problem since u-blox might go out of business and you might
  not want to tell them where you are all time. Their server also might
  be down. There are plenty of reasons to remove dependency to any
  single party.
 
  It is possible to start an open service, with mirrors. Interested people
  can set their freerunners to send in good aiding data when they have it
  (i.e. when using the gps and a network is available.)

 Infos downloaded from u-blox are only valid for some time. So if
 server is down for more than just a short time, it won't help much.
 And I did not check but not I am not sure u-blox terms of service
 allow to redistribute...

I may be misunderstanding the suggestion, but I don't think it had anything to 
do with data from ublox. The suggestion was to use data sent by other 
freerunner users instead of the data supplied by ublox. 

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Re: thoughts on A-GPS offline

2009-02-18 Thread Cédric Berger
On Wed, Feb 18, 2009 at 17:49, Al Johnson openm...@mazikeen.demon.co.uk wrote:
 I may be misunderstanding the suggestion, but I don't think it had anything to
 do with data from ublox. The suggestion was to use data sent by other
 freerunner users instead of the data supplied by ublox.

As I understood the suggestion was in reply to :

 It is not a problem that user account is required when download u-blox online
 aiding data.
 It is a problem since u-blox might go out of business and you might
 not want to tell them where you are all time. Their server also might
 be down. There are plenty of reasons to remove dependency to any
 single party.

The problem is that data from u-blox is a proprietary format, and as
far as I know, we do not know yet how to create the same data that can
be pushed to the GPS chip.
So for now we need to get this info from u-blox . Hence the account
problem. I understood the suggestion just as way to cache this info in
response to the availability problem for u-blox online service.

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Re: thoughts on A-GPS offline

2009-02-17 Thread Rikard Nilsson
 What about if we hack the data format of u-blox AGPS offline file, and
 extract data for current location and time? location can be specified by
 clicking map, time from local system time. If we could, we would be able to
 submit data to GPS chip as AGPS online message on demand. What do you think?

Wouldnt it be possible to get the location from the gsm-network in some way?

/Rikard

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Re: thoughts on A-GPS offline

2009-02-17 Thread Ed Kapitein
Hi Rikard,

Yes, take a look at www.opencellid.org.
This will give you your rough location and you can use that to get the
agps data for your area.

I have some scripts that will do that for you, so just let me know if
you are intressted.

Kind regards,
Ed

On Tue, 2009-02-17 at 09:24 +0100, Rikard Nilsson wrote:
  What about if we hack the data format of u-blox AGPS offline file, and
  extract data for current location and time? location can be specified by
  clicking map, time from local system time. If we could, we would be able to
  submit data to GPS chip as AGPS online message on demand. What do you think?
 
 Wouldnt it be possible to get the location from the gsm-network in some way?
 
 /Rikard
 
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Re: thoughts on A-GPS offline

2009-02-17 Thread Risto H. Kurppa
On Tue, Feb 17, 2009 at 10:40 AM, Ed Kapitein e...@kapitein.org wrote:
 Hi Rikard,

 Yes, take a look at www.opencellid.org.
 This will give you your rough location and you can use that to get the
 agps data for your area.

 I have some scripts that will do that for you, so just let me know if
 you are intressted.

 Kind regards,
 Ed

Yes we're interested!
Show us what you have. I'd like to see things like these to be easy to
install  use, an ipkg package would be nice :)
When someone posted the agps program to opkg.org I was inspired to try
it and it seems to work very well, it's fast to get the fix. If agps
would get the rough location information from opencellid I suppose it
would be even faster (though gprs connection is the thing that slows
down this a lot). But using only opencellid would give you a rough
estimation of the location quickly also when you don't have time to
run gprs to download the agps data. Then if only this rough location
could be given to GPS so apps (tango, navit etc) could use it..

r

-- 
| risto h. kurppa
| risto at kurppa dot fi
| http://risto.kurppa.fi

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Re: thoughts on A-GPS offline

2009-02-17 Thread Timo Juhani Lindfors
Ed Kapitein e...@kapitein.org writes:
 I have some scripts that will do that for you, so just let me know if
 you are intressted.

Note that we can get the whole opencellid.org database and access it
offline.



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Re: thoughts on A-GPS offline

2009-02-17 Thread Timo Juhani Lindfors
mqy meng.qing...@gmail.com writes:
 I think get locations by cell id is especially useful in case of weak or no
 GPS signals.
 I'll have a look at opencellid, thanks.

Note also that ogpsd of frameworkd supports sending this off-line
aiding data.



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Re: thoughts on A-GPS offline

2009-02-17 Thread Rikard Nilsson
would it be possible to get the satelite information that we get from
u-blox from somewhere else?
somewhere that dont require user account?

/rikard

On Tue, Feb 17, 2009 at 12:41 PM, Timo Juhani Lindfors
timo.lindf...@iki.fi wrote:
 mqy meng.qing...@gmail.com writes:
 I think get locations by cell id is especially useful in case of weak or no
 GPS signals.
 I'll have a look at opencellid, thanks.

 Note also that ogpsd of frameworkd supports sending this off-line
 aiding data.



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Re: thoughts on A-GPS offline

2009-02-17 Thread Ed Kapitein
Well, i put a tarball together with my scripts and put it on my website.
http://www.kapitein.org/openmoko
Please read it carefully before installing.
All feedback is welcome ofcourse.

Kind regards,
Ed

On Tue, 2009-02-17 at 11:42 +0200, Risto H. Kurppa wrote:
 On Tue, Feb 17, 2009 at 10:40 AM, Ed Kapitein e...@kapitein.org wrote:
  Hi Rikard,
 
  Yes, take a look at www.opencellid.org.
  This will give you your rough location and you can use that to get the
  agps data for your area.
 
  I have some scripts that will do that for you, so just let me know if
  you are intressted.
 
  Kind regards,
  Ed
 
 Yes we're interested!
 Show us what you have. I'd like to see things like these to be easy to
 install  use, an ipkg package would be nice :)
 When someone posted the agps program to opkg.org I was inspired to try
 it and it seems to work very well, it's fast to get the fix. If agps
 would get the rough location information from opencellid I suppose it
 would be even faster (though gprs connection is the thing that slows
 down this a lot). But using only opencellid would give you a rough
 estimation of the location quickly also when you don't have time to
 run gprs to download the agps data. Then if only this rough location
 could be given to GPS so apps (tango, navit etc) could use it..
 
 r
 


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Re: thoughts on A-GPS offline

2009-02-17 Thread mqy

It is not a problem that user account is required when download u-blox online
aiding data.

The download protocol is fairly simple, can be implemented within several
hours in C.
(1) appaly for a free account by sending a email to u-blox 
(2) format request package by filling in user/password/lat/lon and other
optional data such as pacc,
(3) submit request and get response data, 
(4) parse aiding data from the reply (it's a block of binary data after
header lines),
(5) write the binary data to GPS device. The binary data block contains
about 50+ individual
aiding messages

The account is free. AFAIK, u-blox AsssistNow service should be one of the
most open/free 
A-GPs services, and the up-to-14 days offline data is very attractive
comparing to others.
What I'm concern is: don't know how to eat the big cake without knowing
the format -- 
unlike online data, there is no ubx binary message headers (0xB5, 0x62)
inside offline file.

I guess, each alp file (N days) should be contains the following data:
time range(from, to): each file contains data of [1,2,3,5,7,10,14] days
region IDs: the earth is divided into R regions each cover a (lat/lon?)
area.
satellite IDs: 24 satellites each has it's unique orbit.
region visible satellites: at any time only several satellites visible to a
user.
differential almanac correction data: for each satellite (at the unit of
hours).

Nothing helps regardless where the data come from,
if either don't know how to extract aiding data from offline data, or data
format in-compatible.


Rikard Nilsson wrote:
 
 would it be possible to get the satelite information that we get from
 u-blox from somewhere else?
 somewhere that dont require user account?
 
 /rikard
 
 On Tue, Feb 17, 2009 at 12:41 PM, Timo Juhani Lindfors
 timo.lindf...@iki.fi wrote:
 mqy meng.qing...@gmail.com writes:
 I think get locations by cell id is especially useful in case of weak or
 no
 GPS signals.
 I'll have a look at opencellid, thanks.

 Note also that ogpsd of frameworkd supports sending this off-line
 aiding data.



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Re: thoughts on A-GPS offline

2009-02-17 Thread Timo Juhani Lindfors
mqy meng.qing...@gmail.com writes:
 It is not a problem that user account is required when download u-blox online
 aiding data.

It is a problem since u-blox might go out of business and you might
not want to tell them where you are all time. Their server also might
be down. There are plenty of reasons to remove dependency to any
single party.


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