Difference in cruise control speed and Google Maps GPS speed

I had set the CC at 110 kmph, and just out of curiosity, tried to cross check the speed with GPS, which was showing actual speeds between 95-100 kmph.

jigar1791@gmail recently shared this with other BHPians.

Background -

I drive a 2018 Ciaz Petrol MT. Recently, I was on a 500 km drive from Mumbai to Ahmedabad, and had used the cruise control feature a few times on the NH, especially on the Vadodara-Ahmedabad Expressway (National Expressway-1).

Problem Statement -

I observed a huge difference in the actual speed while using the cruise control (here after: CC) and while verifying it with Google Maps (here after: GPS). I had set the CC at 110 kmph, and just out of curiosity, tried to cross check the speed with GPS, which was showing actual speeds between 95-100 kmph.

I also tried to measure my speed with a GSRTC’s Volvo, as I knew it’s speed was restricted to 95 kmph, and I somehow felt I took longer to overtake the Volvo (I’m at 110, Volvo at 90-95).

Conclusion -

This makes me wonder if the CC speed set function shows reduced speed than it’s set at? Or is there something else? Have fellow Ciaz owners/CC users made a similar observation?

Here's what paragsachania had to say on the matter:

This has nothing to do with Cruise Control but this is exactly how the numbers are displayed/pointed in the speedometer console, which is always higher than the GPS speeds which is a measurement of true speed.

This is mostly the case with almost all the cars, few with a very high variance too. Ideally, there is a difference (speedo error) of around 4-6% and that means if your speedometer shows 100 kmph, your true (GPS) speeds will be around 95-96 kmph.

You can try by just setting the navigation on Gmaps and then compare that with the speed shown on the car's instrument console and you will notice a similar error.

When you set the CC to 100 kmph, it will maintain the car's speed at 100 kmph but with respect to the car's speedometer reading. And hence, it will be more than what your GPS device is to indicate.

There is also a reason why this is done. You can read it on this thread.

Check out BHPian comments for more insight and information.