Home PageFacebookRSS News Feed
PocketGPS
Web
Read the current newsletter! Weekly
Newsletter
SatNav,GPS,Navigation
MacFixer, the iPhone, iPod, and iPad specialists
Pocket GPS World - SatNavs | GPS | Speed Cameras: Forums

Pocket GPS World :: View topic - SiRF Limitation?
 Forum FAQForum FAQ   SearchSearch   UsergroupsUsergroups   ProfileProfile   Log in for private messagesLog in for private messages   Log inLog in 

SiRF Limitation?

 
Post new topic   Reply to topic    Pocket GPS World Forum Index -> Advanced GPS Lounge
View previous topic :: View next topic  
Author Message
Sonex293
Occasional Visitor


Joined: Oct 22, 2003
Posts: 8

PostPosted: Wed Jun 02, 2004 11:13 pm    Post subject: SiRF Limitation? Reply with quote

I was reading the Controlvision forums and found this statement and was wondering if it was totally true. I'm more interested in the SiRF part then the software part....

==============================================

SiRF Chipsets do not output WAAS corrected NMEA data. Almost ALL other GPS manufacturers do output WAAS corrected NMEA data. SiRF is about the only manufacturer to not output the data except in their Proprietary Binary Protocol. To enable us to use the Binary protocol, we would have to purchase a license to use that protocol from SiRF. If you want a WAAS corrected signal, the easy answer is to buy a GPS that outputs WAAS in its NMEA stream. If you want to flame us about not supporting a proprietary GPS data stream format for WAAS accuracy, go ahead, its not that big of a deal, if you want the correction you can get it with the software that is already there, you just need a GPS that outputs it in NMEA. We only support the NMEA protocol, and it is NOT a antiquated way of communicating with the GPS. This is propaganda put out by a few manufacturers that want you to believe that you should use their proprietary binary format over NMEA, so that you will be required to use one of their GPS's ;) Anyhow, enough on this subject. If you want WAAS, get a GPS that outputs it in NMEA..
_________________
Jay Kramer [email protected]
Programmer/Network Administrator
Control Vision Corp.
620-231-6647
Back to top
View user's profile Send private message
DavidW
Pocket GPS Moderator
Pocket GPS Moderator


Joined: 17/05/2003 02:26:21
Posts: 3747
Location: Bedfordshire, UK

PostPosted: Thu Jun 03, 2004 12:07 am    Post subject: Reply with quote

The information in that post is almost completely wrong.


Full information is available online for all but the latest refinements to the SiRF binary protocol (some of new SiRF features in 2.30 and later firmware is poorly documented in freely available sources - SiRF's up to date "SiRF Binary Reference Manual" is sadly not freely available; I only know of its existence because of mentions of it in other places). The older "SiRF messages" PDF which gives perfectly usable documentation on all the 2.20 features and even some 2.30 and later features is available from various places online.

A couple of minutes with Google dug up http://www.falcom.de/pub/sirf/SiRFmessages.pdf - which has had a few words changed to say Falcom, but is pretty much a verbatim copy of the old documentation for the SiRFstar IIe/LP evaluation receiver (see the top of page 5 to see what I mean). As various GPS vendors make this documentation readily available (u-Blox make a better version available to anyone who registers on their web site), I can't see how SiRF can demand a licence fee to implement their protocol. They may be demanding fees to get documentation directly from them, but you don't need to go to SiRF to get usable documentation.


However, you don't need to implement SiRF binary mode to get WAAS corrected positions. Certainly with recent SiRF firmware (my experiments are with version 231.000.000ES), if a SiRF based GPS is configured to use SBAS (the generic term for systems like WAAS and EGNOS), it will output SBAS corrected positions in NMEA mode if it is receiving usable SBAS data.

I may still have some NMEA output somewhere from my SiRF based Haicom HI-303MMF using the test EGNOS signal when it was easy to pick up from PRN 120 in the UK last year. Certainly, the GGA sentence showed in the usual NMEA way that the position fix was differential - the flag that is 1 when it's an SPS fix changed to 2 for a differential SPS fix.

This is one thing that is pretty much documented in a PDF available from the SiRF web site - see http://www.sirf.com/Downloads/Technical/NMEA%20Reference%20Manual%20-%20Addendum.pdf (and note that 2 is not marked as not supported in table 1-4).


On that early test signal, it was debatable as to whether EGNOS was improving or worsening my position - this will not be the case when EGNOS is launched!



David
Back to top
View user's profile Send private message Send e-mail
Sonex293
Occasional Visitor


Joined: Oct 22, 2003
Posts: 8

PostPosted: Fri Jun 04, 2004 11:18 pm    Post subject: Reply with quote

Jay's response.....

http://forum.controlvision.com/viewtopic.php?t=471&start=15

--Mike
Back to top
View user's profile Send private message
DavidW
Pocket GPS Moderator
Pocket GPS Moderator


Joined: 17/05/2003 02:26:21
Posts: 3747
Location: Bedfordshire, UK

PostPosted: Sun Jun 06, 2004 3:00 pm    Post subject: Reply with quote

The licence issue is something I'm not aware of, not being a GPS software developer myself. It's the first time I've heard this mentioned - you would have thought that SiRF would want people to develop to their protocol, but it's their decision.

Unless the protocol is protected by patent, then, if the documentation is freely available (as it is), I can't see how SiRF can stop you developing software that uses their protocol. There's no restriction on use in any of the documentation that I've found.

As I have no intention of developing software myself, I'm not going to check this with SiRF.


The altitude stuff in that thread is confused. In NMEA mode, GPS receivers return altitude above an ellipsoid, and have what I understand is the option of returning a correction between the ellipsoid and the geoid altitude.

SiRF GPSes with firmware earlier than 2.30 do not return a geoid correction, which is believed to be permitted by the NMEA 0183 standard. From 2.30 onward, they do return a geoid correction, but they appear to do so differently to other brands. Without sight of the NMEA 0183 standard, it's impossible to be sure exactly what is and isn't allowed. This standard costs serious money, which I'm not prepared to pay.

I don't have access to SiRF documentation other than what is freely available on the Internet; I'm pretty sure SiRF would want paying, and, as I'm not being paid for anything to do with GPS, I'm not going to pay SiRF.


I have documented the SiRF altitude behaviour comprehensively in the forums before. Take a read of this thread and the thread I mentioned in my first post in that thread.


One final thing - when posting links to this forum, drop the sid element of the URL, otherwise you can get various session related weirdness.



David
Back to top
View user's profile Send private message Send e-mail
DavidW
Pocket GPS Moderator
Pocket GPS Moderator


Joined: 17/05/2003 02:26:21
Posts: 3747
Location: Bedfordshire, UK

PostPosted: Sun Jun 06, 2004 3:01 pm    Post subject: Reply with quote

One more thing - there are plenty of tools available that allow you to switch SBAS on and off on SiRF based GPSes. Some of them are written by SiRF based GPS vendors, so I can't think there's any legal issues in using them.

Switch to SiRF mode, switch on SBAS, and switch back the NMEA mode - then, as long as the internal battery doesn't go flat, the GPS will continue to output NMEA sentences with SBAS correction.



David
Back to top
View user's profile Send private message Send e-mail
ckuethe
Occasional Visitor


Joined: Aug 08, 2004
Posts: 18
Location: ECEF X/Y/Z: -1514741/-3483783/5106784 m

PostPosted: Mon Aug 09, 2004 1:56 am    Post subject: Reply with quote

At the risk of sounding like i'm spamming, I'd like to mention that I've got a GPS toolkit in PERL on the go. It's still pretty alpha (more decoders to write, more control interfaces needed, etc) but already it will do fun things with the binary protocol. Enabling SBAS by default and using the SiRF protocol at the highest speed available are on my to-do list.

As for implementations of the SiRF protocol:
* I never received any document restricting my use of the SiRF protocol when I purchased my SiRF based gps.

* There are no posted restrictions on the use of the SiRF protocol on my vendor's webpage.

* Any "reverse engineering" which may occur in the course of using the SiRF protocol is for the purposes of maintaining or introducing compatibility with the SiRF products

*CV's claim that using the SiRF protocol requires you, the end user, to get a license is bogus. If anything you are already licensed to use the protocol because when you got your SiRF based gps, your vendor sublicensed the IP and protocol to you.

* I have found no indications that the protocol is patented. One of SiRF's partner companies claimed it was a trade secret, but I think that's bogus. I found the document in their public downloads section and the documentation is available without restriction from multiple vendors. To me this indicates that trade secret status has been lost, as it was not properly protected. Furthermore, no significant competitive advantage or economic benefit is gained by non-disclosure, thus treating the protocol as a trade secret would've been silly in the first place.

* Perhaps where the might get you is on the fact that you're allowed to make one copy of their website for personal use, so be careful that you don't use what you read there for profit. Or something. SiRF eval kits are so cheap ($220CDN, $161US, 88GBP) making it a small price to pay for your R&D program. Furthermore, their licensing documents make no mention of requiring a license to use SiRF protocols or published interfaces. They require licenses for source and object code, as well as ARM cpu, but they don't seem to care what bits you exchange with your gps.[/list]
Back to top
View user's profile Send private message Visit poster's website
ckuethe
Occasional Visitor


Joined: Aug 08, 2004
Posts: 18
Location: ECEF X/Y/Z: -1514741/-3483783/5106784 m

PostPosted: Wed Aug 25, 2004 5:04 am    Post subject: Reply with quote

I'm pretty sure no license is required to implement the protocol. I just emailed SiRF to ask for updated protocol documentation, and explained why I wanted it, and they sent the latest revision with nary a whimper. All sorts of goodies to be found... Wheeee!
_________________
http://www.ualberta.ca/~ckuethe/gps/
Back to top
View user's profile Send private message Visit poster's website







Posted: Today    Post subject: Pocket GPS Advertising

Back to top
Display posts from previous:   
Post new topic   Reply to topic    Pocket GPS World Forum Index -> Advanced GPS Lounge All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

Powered by phpBB 2.0.11 © 2001 phpBB Group
phpBB port v2.1 based on Tom Nitzschner's phpbb2.0.6 upgraded to phpBB 2.0.4 standalone was developed and tested by:
ArtificialIntel, ChatServ, mikem,
sixonetonoffun and Paul Laudanski (aka Zhen-Xjell).

Version 2.1 by Nuke Cops 2003 http://www.nukecops.com

Make a Donation



CamerAlert Database

Click here for the PocketGPSWorld.com Speed Camera Database

Download Speed Camera Database
20.064 (22 Jun 22)



WORLDWIDE SPEED CAMERA SPOTTERS WANTED!

Click here to submit camera positions to the PocketGPSWorld.com Speed Camera Database


12mth Subscriber memberships awarded every week for verified new camera reports!

Submit Speed Camera Locations Now


CamerAlert Apps



iOS QR Code






Android QR Code







Terms & Privacy


GPS Shopping