GPS and MOTEC

[W. Tripp]

With all of the recent posts about GPS, I thought some of you might be interested in a project a few of us have been working on.

Over the past couple of months, Dewitt Deweese III (Dock Rocket), Daryl Lane, and myself have been working with a tech guru at Motec, USA (JGM) on a GPS reciever and software that will allow us to run a 1/4 mile pass anywhere on any body of water and recall ET's and speeds throughout the pass, all without having to use a stopwatch on a measured course. This added to the onboard accelerometer and data logging dash units we are now using, should prove to be a great tool for the drag racers among us.

One of the problems we have encountered along the way has been that civilian GPS units only operate at 1Mhz (once a second) - this is too slow for my 1900 lb Lakeracer, and not even close for the methanol/nitro burning "Dock Rocket". The graphs of the run look more like steps than a true curve. We should soon have a unit that works at 20 Mhz - that should do the trick.

Another problem we have to deal with is that when GPS units are run over the imaginary boundary lines that divide up the WGS 84 map (the map most GPS units use) the unit will not be able to make the location/speed calculation accurately and can cause an error. This has now been worked out, but explains the strange errors that somtimes occur with my hand held XL12.

Over the next few months this unit should become available to the public as a stand alone unit or as an addition to the Motec data logging dash unit. Daryl Lane at Boatworks ( http://www.boatworks.net ) can give those who are truely interested more info.

I hope this helps.

[Tony Brucato]

Wayne,

Will you be able to create an aceleration curve from the GPS data similar to the Stalker radar software?
Will the unit do more than just 1/4 mile tests?
It would be great if you could program in your own test paramaters like 0-30, 50-70, or whatever.
What do you think the cost will be for the stand alone unit?
It sound like this will be a leap forward in on-water testing.

Tony

[BarryStrawn]

Hi Wayne,

Glad to hear you are making progress with GPS. We exchanged some emails last December when you were working on an accelerometer package. Glad to hear you all found a unit that would work. By the way, a MHz is a million cycles per second but we know what you meant.

I ended up buying the beginnings of a RacePak VNet system. Discussed the GPS with them some and they didn't have much they were willing to talk about. Sounded like they had some success in circle track testing using other sensors at the start/finish to close the loop on the GPS and accelerometer integrations. Cost seemed to be the issue. I hope the RTK stuff becomes afforable soon.

Thanks for the update,

Barry

[W. Tripp]

We have been able to show curves for all of the information the dash collects (egt, engine temp, air temp/density, accel., gps, rpm, tps, spark resistance, etc.......). If it is a 5.5 volt sensor, it is easy to use. We can overlay curves from past runs and compare to our most recent testing. Most of this info can be downloaded from the ecu after the run, but with the dash, it can be viewed real-time or recalled after a run.

The GPS info has been set up to show data at 60 ft., 1/8 mi., 1000 ft., and 1/4 mi., with speeds shown. It is easy to look at the graph of the curve and find what info you might want, or to add points allong the curve for 0-30 mph, 0-60 mph, 60-100 mph, 100-Mach 6, etc.

If all you are wanting to do is data-log, take a look at the Data-mite unit from Performance Trends -
http://www.performancetrends.com/dtm-hdwe.htm

The cost is reasonable and two units are available for whatever you might want to do. They even have a plug in accelerometer to go with this unit.

I hope this helps.