02 April 2006

How to tell railroad tracks from roads in aerial images

In previous posts (here and here), STUFIT* presented aerial photos of trains. Today, we show you how to distinguish railroads from ordinary roads in aerial photos.

This picture shows a divided road with 2 lanes on each side.

rd1

And this is what 2 sets of parallel tracks look like.

trcks1

Any questions?

For one thing, there are usually cars on roads. One normally doesn't see cars on railroads, although I have occasionally seen special trucks with train wheels on railroads. Also, roads intersect with other roads and make sharp turns. Near the lower lefthand corner of the picture above, you can see one side street intersecting at right angles with the main road. Two railroads never intersect with each other like that.

The main distinguishing feature of railroads visible in aerial photos with high enough resolution is the parallel tracks running very close to each other. This is something one wouldn't see on roads. In the picture below, compare the appearance of the tracks on the right with that of the road on the left.

rdtrcks


Photos are from Terra Server.


*Snail’s Tales’ Useless Frivolous Information Team

1 comment:

John said...

Electrified railroads will also have catenary structures. These usually have pretty distinctive shapes made visible in the shadows they cast on the ground.