Distance travelled tracked by gps

[davidfla90]

Hey,

I'm relatively new to LabView. Im currently planning a project that tracks your gps distance traveled. This system will be placed on a wheelchair. I just need some help and guidance, on what i should be looking into and researching. (Gps systems, programmes, websites. etc)

Thanks you.

[PhillipBrooks]

I worked years ago on cellular wireless coverage inside of buildings. I think you will find that GPS is not going to work well (or at all) indoors

If you wish to measure the distance travelled for your subject (the wheelchair), you may need to combine GPS with dead-reckoning. You would use encoders on one or both wheels and measure the number of rotations for each wheel and determine the X-Y distance travelled when inside.

[rex1030]

Yea the wheel counter would be the easiest method. GPS will be good outdoors but signal problems will be an issue. Internal navigation systems are expensive but effective.

Even if you do use gps, you have some fun ahead. You should look into the NMEA different strings that GPS devices use to output their postition data, like GGA and such. You should get familiar with tokenizing and regular expressions if you want to start reading gps strings. Also, A lot of high end gps devices have internal dead reckoning that is automatically calculated and outputted as one of the gps strings with velocity and direction. Once again, these devices can get expensive.

Perhaps if you shared some of your initial plans for what you had in mind for a system to accomplesh your goals, we could be mroe help.

[Rhys - AE]

Hey there!

I agree with idea of considering the simplest possible solution for your problem, like the wheel counter. It really is the bane of us engineers that we love to implement the most complex, albeit coolest, solutions and open the most ridiculous can's of worms in the process.

However, if your heart really is set on using GPS then the example linked to this post should prove invaluable! I've used and manipulated it myself in the past, but you'll get alot more out of it by doing some reading into the NMEA protocol as Rex suggests. Even if you start off with Wikipedia!

Read GPS Time, Position, Velocity, and Course Heading

http://zone.ni.com/devzone/cda/epd/p/id/2197

I hope this proves helpful! If there's anything else we can do then jus post back.

P.S. Specific questions yield specific answers! It's almost my motto as an AE.

[davidfla90]

Hey,

Sorry about the delayed reply.

The initial and main goal for the project is to be able to measure the distance traveled by a wheelchair bound athlete. I would also like to expand this project and be able to map his position.

I really find the Inertial navigation system very appealing, and very very cool.  In terms of complexity and time, how much longer would it take to understand and complete an INS compared to GPS.

Could anybody recommend a GPS unit?

[RTSLVU]

If you do go with the GPS,just make sure the one you get has a serial port and communicates in NMEA standard messages.

These messages are plain text and are constantly transmitted from the GPS (you do not query the GPS) and it is just a matter of waiting for the NMEA "sentence" that contains the information you are interested in to be transmitted and parsing the text.

Here is a good website on decoding the NMEA sentences http://www.gpsinformation.org/dale/nmea.htm

[mikealder]

If you don't need the distance travelled in real time then post processing a text file stored in a GPS data logger would be a better approach as these are typically matchbox sized, battery powered, self contained and light weight. Positional data, heading, speed etc is written to a text file which is stored on a MicroSD memory card. The data (text file) can easily be be read by Labview and performing a distance calculation between positional updates is easy.

Another option would be to store the GPS data on a PDA that contains a GPS receiver, most HTC PDA based phones running Windows Mobile have integral GPS receivers and can be programmed using the PDA Labview application. The PDA application for use with Labview is rather limited in what you can do with it, it will work but don't expect too much from the display and it will hammer the battery in the PDA.

As for a GPS data logger the device I use is a Columbus V900, these are not too easy to obtain in the UK but can be sent over if bought from a USA supplier (typical price is around £80), this GPS logger records data once per second, there are other units that can datalog at higher rates such as 5 Hz even 20Hz is available at a significant cost (20Hz unit cost around £1600 last time I looked in to such a unit). The higher the sample rate the better the route definition from the data, this can be handy if you want to examine trajectory through a corner to optimise exit speed for example, graphing where a wheelchair has been using a GPS data logger is also very easy using Labview.

Last time I tried doing similar was tracking race cars at Mallory Park in the UK, I used a 5Hz and 1Hz GPS data logger, post processing the data was performed on my laptop using a Labview application, if you need any more info on what I used/ program etc just ask and I can post up more details later today - Mike