Is there any application that gives you GPS and altitude data?

I defined a test already and I would like to compare the altitudes measured by different sources. I drove a path by a car, mounted a GPS and a pressure sensor in the vehicle. On the chosen path, there were many high bridges over the highways. Both gps and the pressure sensor detected the bridges, however, at this point I would like to compare them both to an external trustable source which gives me the real and true altitude.

I tried "gpsvisualizer.com" but it seems that it does not consider the bridges and their heights from the ground. Is there any application I can use for this purpose ?