Factual error: When the UBoat changes course, Andrews, operating the radar repeater, is immediately able to provide the bridge with the target's new course and speed. This would be impossible without extensive calculations and at least range and bearing plots once the target has steadied up on the new course, either figured on the scope screen or on a maneuvering board. One must remember that both vessels' courses and speeds must be taken into account when making computations, and the relative direction of a target's travel most often is not its true course.
Factual error: The train's locomotive has a steel cab, an electric headlight, and other modern applications. Overall, it more closely resembles an early 20th century steam engine than that of the 1880's, when the movie supposedly takes place.