GPS speedometeres - are they any good?

[Pills]

Originally Posted by Merv and Sharon

Like many others, I calibrated my speedo with my hand-held GPS. Ensured that it was over reading by about 5kms/hr at 100. Seemed a sensible margin. No one ever tested it for registration. Why use a GPS speedo? I seem to have missed the point.

Hmmm, if you used your GPS to calibrate the speedo, isn't this really a testament to the accuracy of GPS ?

Hi Merv.Not sure if this was directed at me or just an off the cuff remark, but if you read my earlier post I set out some of the reasons for me personally opting for the GPS speedo, mainly space constraints. In my case its also a case that my car is a pre 90's engine /transmition setup and it would require me to carry out significant conversions to adapt to a modern speedo with cable setup. That is I would have to go with a magnetic pickup or similar. Also with a cable setup, I would have a severe bend in the cable to be able to place the speedo where I want on the dash due to the heater/demister. I know there are 90 degree adapters etc. available but i would probably spend months sourcing it all and hours trying to sort it out and would have a final setup whith lots of areas which could fail. My current speedo is driven by a cog directly from the gearbox to the speedo and I have already replaced the cable once, and it was a pain to have the cable made up as it is no longer available.
In my case this is an excellent option, as it is one less cable in the engine bay going through the firewall, and I am not limited to the positioning of the speedo. I also like the features that a GPS speedo offers. It has a 5 hz calculation rate, it can display time direct from GPS, also has a built in 0-100 time and 1/4 mile time feature, also can give you altitude (for those long hill climb trips) as well as the usual trip meter etc. I also get to choose what colour backlighting and pointer colour for night, as well as a dimmer. Its a simple instillation and calibration, and other than power the only connection is the gps antenna which u can locate under the fibreglass dash easily as it is the size of matchbox. The depth of the gauges behind the dash is just over 1 inch with a spin on ring to hold them in place. In my case after playing around with the smiths gauges, this was an easy decission. Another selling point for me was the fantastic night vission, as with the Smiths, they are very poor at night, even after I changed the globes to SMD led globes.
This is my reasoning, and I guess the features important to me might not be to others, but there is a point for them being available.