The epitome of cartographic error would have to be that of Columbus. Many people had a general idea the size of the world pole to pole, but Columbus became convinced that earth was very much oblong (with a "nipple" at the garden of eden). He believed that it was not nearly so far to sail around the earth and reach the far east. He overcame this planetary scale inaccuracy by being lucky.

Keep in mind that the quality of the map goes hand in hand with your ability to tell your position on it. As with Columbus's odd globe, there is a degree of anisotropy when it comes to reckoning. Latitude is relatively easy to determine by star sighting while longitude is much more difficult without an accurate time keeping device. To overcome this difficulty it was a common practice to sail to the correct latitude and then head east or west along that latitude until reaching the destination.

One that comes to mind is Rae Strait being unknown on earlier maps (and it was marked as an inlet, not a strait for awhile). The Rae Strait is supposedly more ice free than the nearby Victoria Strait.

Evidence from the Franklin Expedition indicates that they tried the Victoria strait instead. Nobody survived. So that's one impact. (Although the Franklin Expedition had other issues as well).