Anemometer for travel speed calibration?

[GasSavers_maximilian]

I was trying to think of very accurate ways to calibrate my speedometer and was thinking an anemometer might be a good way to go. I also happen to own one already. They're pretty accurate is my understanding and not too expensive. My work with the coast down math shows it's pretty sensitive to systematic errors in logging the speed and since tire wear can change that sort of thing I want a fast way to recalibrate. Cheap GPS receivers have a mixed reputation for instantaneous accuracy, at least according to the searches I did. I'd just use highway mile markers but I'm not very close to one.

I worry about issues with the air turbulence right next to the vehicle effecting the anemometer, so maybe I'd need to put it on a mast?

The craziest idea I've had so far in my brainstorming has been to make a timed sprayer that marks the road during the coast down test. Then I could measure the mark spacings. Like I said...crazy.

[Jay2TheRescue]

You want to accurately calibrate your speedometer? Use a GPS. An annemometer will be effected by turbulence from passing vehicles, and also by wind.

[GasSavers_maximilian]

I was locked into considering options that have reliable instantaneous accuracy, but for speedometer calibration I don't actually require that. I can average it over a period while maintaining a steady speed. Then I can use the calibrated speedometer to do the coast down. OK, check that one off. Thanks.

[Nrggeek]

You could also use Google Earth to determine the distance along your stretch of road.