Two gps isn’t that much better than one in my experience. Because they’re both subject to the same atmospheric effects.

What I have found is the brand and model make a huge difference.

If you have a GPS with a ublox chip, you’re in good shape. Those chips can pull in a 3d fix in my damn basement. The sensitivity is insane.

I also had great results with Venus chips but idk if any oem uses them. Ublox you can find easily. USB dongles, breakout boards, etc.

The MediaTek chips I’ve used can’t get a fix even outside unless conditions are really good.

Anyway… If you’ve got a gps plugged into a laptop there are utilities to show a sky map and where sats are and which are being received. Usually the chip maker makes a utility like this. (E.g. u-center for ublox)

If it’s a handheld gps there is usually a screen with a similar display.

https://in-the-sky.org/satmap_worldmap.php?gps=1 has a map of satellite positions.

The app GPS essentials is even better though, shows all the GPS satellites above the horizon for your position, in grey until your phone gets a lock-on. Inner circle is 45°, outer is horizon, makes it quick to get a rough idea of where they are in the sky.
Actually, in a dense city you might be better off using a phone. Since it will position you based on cell towers, WiFi Geo mapping, and whatever GPS satellites are visible.

Maybe check for a clock issue. If they are out of sync it can be very hard to get a good gps fix.