Final answer:
The altitude of Polaris, measured at 45 degrees above the horizon, indicates that the observer is at the 45th parallel north or at 45 degrees North latitude.
Step-by-step explanation:
If you measured the altitude of Polaris to be exactly 45 degrees above the horizon line, you are located on the 45th parallel north latitude. The altitude of the North Star, or Polaris, which lies near the north celestial pole, corresponds directly to the observer's latitude when measured above the northern horizon. Therefore, observing Polaris at a 45-degree angle above the horizon means that your latitude is also 45 degrees North.