[LinuxPPS] Using GPS for automotive applications

[Neal Probert]

The Wiki has a few more links.

http://en.wikipedia.org/wiki/Vehicle_infrastructure_integration

Rodolfo Giometti wrote:
> On Sun, Apr 06, 2008 at 10:11:56AM -0400, Neal Probert wrote:
>   
>> VII
>> ---
>> This is a US-DOT funded project with involvement from most of the 
>> automotive companies and a dozen other suppliers/vendors.  There are a 
>> number of experimental public, safety and private applications being 
>> developed.
>>
>>     http://www.its.dot.gov/vii/
>>     
>
> Thanks for the URL, I'll put it on the LinuxPPS's wiki. :)
>
>   
>> Most of work we're doing is still research and development, working to 
>> get the cost of GPS units down and find ways to improve accuracy and 
>> precision in the moving vehicle.
>>
>> DSRC is basically a WiFi link at 5.9Ghz.  We're using Linux because it's 
>> a hell of a lot cheaper and easier to add a new network protocol stack 
>> to an open source operating system.
>>     
>
> I just looked around in the site but I didn't see any reference to
> Linux nor PPS... maybe exists some technical reference page? :)
>
>   
>> The VII testing in taking place in Farmington Hills/Novi in the Detroit, 
>> Michigan area.  Another test area is in California.
>>
>> GPS
>> ---
>> DoD has removed all dilution from the satellite signals.  There is a new 
>> generation of satellites (block III) going up in the next decade or so 
>> that drastically improves the accuracy and precision.  That implies new 
>> GPS receivers, of course.
>>
>> The DGPS signal is sent from a local DGPS base station to the traffic 
>> lights which is broadcast to the test vehicles.  At this point in time, 
>> it's not a significant improvement.  We're probably looking at using 
>> each traffic light as a virtual reference station in the future.
>>
>> Automotive
>> ----------
>> Most automotive GPSes use the speed input from the vehicle, so they can 
>> do a little dead reckoning.  Most consumer grade GPSes are often based 
>> on the ARM chipset, so only support single precision floating point 
>> math.  So SiRF and u-Blox, even with corrections, aren't good enough.
>>
>> For VII, we're doing 100 msec extrapolations based on vehicle speed, 
>> acceleration and yaw available from the vehicle's CAN bus.  A lot of 
>> information is available from modern vehicles because it's used for 
>> anti-lock brakes, traction control systems, vehicle dynamics control, ...
>>
>> Some folks are adding an IMU which helps in cases where you need dead 
>> reckoning in the urban canyon.  Spend a little more money we can get 
>> higher quality (a lot more money in the case of the Applanix) positioning.
>>
>> Linux Kernel
>> ------------
>> The PPS integration is important for DSRC radio synchronization and 
>> keeping the OS clock in sync.
>>
>> So I'm looking at waiting on the 2.6.26 kernel, so it looks like I'll 
>> need to be patching the latest Ubuntu kernels to get what I need.
>>     
>
> Please, try patch ntp-pps-2.6.24-ter.diff.
>
>   
>> So, yes, it would be very handy and helpful to get this integrated into 
>> the kernel as soon as possible.  It would be a huge win for Linux.
>>     
>
> I'm working on it. ;)
>
>   
>> PPS Interface
>> -------------
>> The simplest way I can see interfacing the PPS is through a MAX232 chip 
>> into the serial port's DCD input.  Right?
>>     
>
> Why do you need connecting the PPS signal to the DCD pin? Can't you
> use a dedicated CPU's GPIO?
>
> Ciao,
>
> Rodolfo
>
>   


-- 

        /// ProbeStar Telematics Systems, LLC. ///
    Automotive, Mobile and Embedded Systems Consulting 

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