"They said gps doesn't work good enough for location inside a building or even inside a car."
That is fairly accurate, but there are some gray areas. I spent many years helping customers with permanent GPS installations, so I know.
Most buildings have enough metallic 'crap' in the attic or on the roof that it blocks the signals. A case in point is that much fiberglass attic insulation is backed with aluminum foil. A few buildings are constructed with thin, modern materials that are transparent to the signals. Some buildings have a central atrium with a transparent skylight, so you can get a GPS fix in the center, but not so much toward the outside. Some residences are constructed out of stucco, but that is formed over a metallic mesh, so it blocks signals. GPS can sneak in through a wide window, but that is very unpredictable. In a TEMPEST-rated building, you will get zero signal inside. I've seen people try to install a GPS antenna inside a TEMPEST building, and they will pull out their hair trying. Don't ask me how I know this.
Cars are unpredictable as well, due to the shape. Some cars have a mostly vertical windshield, and others have a very windswept windshield. If you can get the GPS antenna far enough forward underneath the windshield that it can look up and see most of the sky, then that mostly works. But, if it looks up and sees mostly the metal roof of the car, then that doesn't work. Additionally, the GPS view out the side windows is very unpredictable. A few cars have a metallic glazing on the windshield glass, and I think that is a electrical conductor for windshield defrosting and deicing. That metal also tends to block the GPS signal. In contrast, if you can get an external GPS antenna outside the metal chassis of the car, then that tends to work good. Some newer cars have a bunch of cell phone and GPS navigation electronics in them. Most of the time, they put the GPS antenna either outside next to the rear window, or else inside on the rear window package shelf (where it can get a good view straight up). Some cars have an OnTrac system, and it generally puts the GPS antenna back there near the rear window, but it puts the control head in the inside rear view mirror.
So, there are no absolute rules for any of this. You need to stick a handheld GPS receiver in the building or car and test it.