On a sunny day (Mon, 30 Apr 2012 13:36:14 -0600) it happened hamilton <hamilton@nothere.com> wrote in <jnmpjg$hvk$1@dont-email.me>:>On 4/30/2012 10:42 AM, Jan Panteltje wrote: >> On a sunny day (Mon, 30 Apr 2012 00:07:14 -0400) it happened Spehro Pefhany >> <speffSNIP@interlogDOTyou.knowwhat> wrote in >> <bo3sp7dfd9qhdsrac7d3fp31bpn7pfrorb@4ax.com>: >> >> >> >>> GlobalSat or U-blox modules with SiRF III etc. are around $15 shipped. >>> >>> Eg. >>> http://www.dealextreme.com/p/eb-365-gps-engine-board-module-with-sirf-star-iii-chipset-80045?item=4 >> >> Do those modules come with any sort of datasheet? > >Google found this: > >http://diydrones.com/profiles/blogs/cheap-gps-modules-atThanks! I have downloaded the pdfs, maybe I buy one just for fun, could be an other PIC project, and combine with my fluxgate compass... Years of fun ahaead... Maybe needs a more powerful computah, one of those recent Linux based boards perhapds (display maps on LCD etc). ;-) I would not use FAT filesystem ....
What is the cheapest way to get a GPS + solid state gyro?
Started by ●April 29, 2012
Reply by ●May 1, 20122012-05-01
Reply by ●May 1, 20122012-05-01
On Mon, 30 Apr 2012 16:02:07 -0500, Tim Wescott <tim@seemywebsite.com> wrote:>On Mon, 30 Apr 2012 11:09:49 -0700, linnix wrote: > > >>> I'm nearly 100% sure that if you want to do credible dead reckoning you >>> need accelerometers and gyros, not just one or the other. �Gyros don't >>> mean much when you don't know the acceleration, and accelerometers >>> don't mean much when you don't know the vehicle direction. >> >> Why can't you figure out the direction with 2D accelerometers? > >Because without a gyro or some other angular reference you don't know >what direction they're pointed. > >I suppose that if you were really cost-conscious you could assume no >skidding and take sideways acceleration to be an indication of turning >rate -- but that's a pretty tenuous connection to reality.Yes, it's definitely one of those "works in theory but..." applications. But in theory, it would work. ;-) In practice, it could be good enough to work thorough the "urban canyon" effect for brief GPS outages, although the addition of a simple fluxgate compass would help tremendously. -- Rich Webb Norfolk, VA
Reply by ●May 1, 20122012-05-01
On a sunny day (Mon, 30 Apr 2012 13:36:14 -0600) it happened hamilton <hamilton@nothere.com> wrote in <jnmpjg$hvk$1@dont-email.me>:>On 4/30/2012 10:42 AM, Jan Panteltje wrote: >> On a sunny day (Mon, 30 Apr 2012 00:07:14 -0400) it happened Spehro Pefhany >> <speffSNIP@interlogDOTyou.knowwhat> wrote in >> <bo3sp7dfd9qhdsrac7d3fp31bpn7pfrorb@4ax.com>: >> >> >> >>> GlobalSat or U-blox modules with SiRF III etc. are around $15 shipped. >>> >>> Eg. >>> http://www.dealextreme.com/p/eb-365-gps-engine-board-module-with-sirf-star-iii-chipset-80045?item=4 >> >> Do those modules come with any sort of datasheet? > >Google found this: > >http://diydrones.com/profiles/blogs/cheap-gps-modules-atPS I ordered this one: http://www.dealextreme.com/p/em-411-gps-engine-board-module-with-sirf-star-iii-chipset-80037 because it has build in antenna and I do not have to design the GHz stuff. Connections are also much easier to make. It is a bit more expensive, but not if you include all that RF stuff.
Reply by ●May 3, 20122012-05-03
On 2012-04-30, Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:> I noticed when driving a new car in Europe that the nav system managed > to track fairly well through long tunnels. Makes sense that they would > stick an accelerometer and/or gyros in there for when the GNSS > satellite signal is not available- tunnels and urban driving between > tall buildings. Even a lousy MEMS gyro won't drift that many degrees > in a few minutes.Those systems also use the speed/distance information from the wheel sensors, so the can be pretty accurate. A bit like a hi-tech device called odometer ;-) -jm
Reply by ●May 3, 20122012-05-03
On Thu, 03 May 2012 12:57:27 +0000, Jukka Marin wrote:> On 2012-04-30, Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote: >> I noticed when driving a new car in Europe that the nav system managed >> to track fairly well through long tunnels. Makes sense that they would >> stick an accelerometer and/or gyros in there for when the GNSS >> satellite signal is not available- tunnels and urban driving between >> tall buildings. Even a lousy MEMS gyro won't drift that many degrees in >> a few minutes. > > Those systems also use the speed/distance information from the wheel > sensors, so the can be pretty accurate. A bit like a hi-tech device > called odometer ;-) > > -jmIf you can be pretty sure that there's no skidding going on, an odometer and a steering-position sensor should be able to mostly or completely replace gyros, accelerometers, etc. Of course, the more sensors, the merrier. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
