Consumer GPS is not as precise in Italy as North America?

Question

I&rsquo;m spending some time in Bologna, and one thing I noticed is that while the data you get for you cell phone is very fast (many people don&rsquo;t bother to use wifi) GPS feels noticeably less precise. I can&rsquo;t be imagining this can I? In Mexico/USA it&rsquo;s usually very accurate, but here sometimes off by a block or two&hellip;

drewbee · Accepted Answer

Italy has some of the most difficult environments for GPS I have ever seen. Narrow alleys with 5+ story buildings. I have not been able to find restaurants using GPS to guide me, or even the block they are on. It's due to multipath and limited sky view.In open sky GPS accuracy would be about the same in the North America and Italy. There is a GPS correction service used in Europe and North America called SBAS. If you outside an area with SBAS (for example China) you will typically get a meter or two less accuracy. China has a different map datum that can be 1KM off due to some cold war era policy that now seems more about protectionism. Other than China map datums are consistent with GPS positions.

toast0 · Answer

Are you in the city or just around it? A quick look suggests the city could be difficult GPS territory with its tightly packed buildings and narrow streets. Nothing like a downtown full of skyscrapers, but still somewhat difficult and may have multipath reflected reception.Also, sometimes the orbits just don't work out for visibility of enough satellites to get a high quality position (if your receiver can use GPS and one of the other GNSS, that helps a lot, you're unlikely to have poor orbital pathing on two or three systems simultaneously)

gvb · Answer

Are your maps using the same datum as your GPS (WGS 84)? That is likely the source of the discrepancy. If they are using the same datum, I suspect your maps are off, not your GPS.https://en.wikipedia.org/wiki/World_Geodetic_System