Your smartphone's GPS uses both your cellular and Wi-Fi connection for accuracy. Most of the time, when you're in the car or walking outdoors, the Wi-Fi is turned off to save battery power. Yes, your GPS will work with just cellular, but it's not as accurate as when you also have the Wi-Fi turned on as well, since the GPS has an error rate of +/- 100 feet.
To increase your GPS accuracy, just turn on your Wi-Fi. You don't have to be connected to a Wi-Fi hotspot for the GPS to benefit from it, it just has to be turned on!
Other factors that affect GPS accuracy are whether there are physical obstructions between your phone and the satellites, such as walls, building and trees, so make sure you have a clear line-of-sight between your phone and the sky. Your GPS is most accurate when it can "see" all 4 satellites. It will still work with fewer, but again, the accuracy will be affected. Your GPS may work despite these obstructions, however, its accuracy may be affected significantly.
Although when driving, 100 feet may not make much of a difference, it does when you are walking or hailing an Uber, otherwise the driver may think you are 1-2 blocks from your actual location! If you want to make sure you're located at an exact address for an Uber pickup vs. depending on the GPS to "pin" you accurately, type in the actual street address of your location!
I love technology and how it enhances our lives! Just think, without the Apollo moon missions, we might not have calculators! Imagine!!