gstq54, let me know if I understood correctly the problem. You have two id systems: One RFID (buried loop antennas I assume, i.e., the tag readers) and a GPS, which you want to combine. The vehicles move among several sites. Do the rfid tags come from an access control system? . Are the location and the time that the vehicle is in a specific area of a same site, significant? . Is the GPS necessary just for outside location? .  

1) GPS tags have aleady been invented and are widely available.

218,000 (!) hits on:
www.google.com/search?q=gps+tags

2) Pay attention to the accuracy specs for GPS.  There can be a lot of cars within a 30m circle (for example).  You might want to include a reference GPS at the server and do your own differential adjustment to narrow the location down to a much smaller area.

 

Good point VE1BLL, still, my question remains.

Thanks for the input
I will do a little more research with regard to GPS tags.
However this is a very low budget project and cost per tag is important.
Let me expand a little.

We are looking to track the location of new vehicle inventory at a car dealership. The dealer has in excess of 1000 vehicles in inventory at any one time. These vehicles are stored on different lots within close proximity to the dealership. All lots are outside and unobstructed.

The idea is to use a portable RFID reader and GPS (we have a waas enabled reader) to track the approximate location of each vehicle. An accuracy of between 25 and 50ft should suffice.
Each vehicle would have a tag attached and then as the reader picks up the tag the tag is read and the location recorded. That data is then transmitted to a central server.

We started looking at active tags from Wavetrend. They transmit every 1.5 seconds and have a battery life of about 4-5 years at a cost of about $12/tag. However I am now looking at a new company http://trolleyscan.com/isosys.html who offer a passive tag for a cost of approx $3/tag.

At some point we would also set up static readers at vehicle access points to record when a vehicle entered or left a particular lot.

What often happens is a customer will come in to test drive a specific vehicle based on a web inventory search. That vehicle may be at the back of lot 3 so knowing its location in advance would be very helpful. The lots are packed with vehicles and often times several vehicles have to be moved to get to the requested unit. Also older vehicles tend to get stuck at the back of a parking area when they really should be displayed and sold prior to newer units.

So my thought is that what I need is some kind of hardware device (mux? data-logger?) that will buffer the rfid tag data followed by the GPS data and then transmit that combined data to the serial port on the server. That data would be separated into tag and gps data and update the inventory database.

Sorry for the ramble and thanks again for the help.

Regards

I faced a similar problem some years ago regarding the distribution fleet of a bottler company. Three main, and independent, issues were considered: Security outside the facilities (“road navigation”), access control and displacement inside the facilities. In that case, the operating responsibility for each of the three activities was clearly different. The first implemented system was the access control through RF tags (Motorola/Indala or equivalent). Then, the inside displacement monitoring system –needed for operating purposes-, was set up as an extension of the access control. You may note that these two issues were of company’s responsibility. The GPS (tags) system was also considered but not implemented, at that time, by the haulage contractors.

Regarding the hardware, all the readers were serial. It was necessary to split up the readings from common readers to two separate computing systems (security & operations). Nothing complicated. The costs were not low nor expensive. However, if you face a trucker, his vehicle, the streets, etc., the system must be very robust.

I hope this may be useful.

Much depends on how much software you're planning on writing.  If the answer is little to none, then perhaps a laptop with a GPS receiver and a serial link to the RFID transceiver would at least allow you to use Excel or Access with VBA to enter the data.

With more software, you could probably get a GPS equipped Palm and serial beam the RFID data into the Palm.

TTFN

Hi, gstq54 I'm wondering if you can elaborate on what you ended up doing for the car dealership? Did you decide on a specific course? How did you work the gps and the rfid tags into the same system, and did the passive tags work out? Thanks for any info!