Guild Wars 2

While many skills give precise distance specifications, 600 units etc.

How can one know for sure what these distances really are other than trail and error?

Is there any yardstick or other thing in the GW2 world we can use to measure distances, so one can know for certain what 600 units represents?

Are there things that have a known lenght in distance units?

When I started, I just inched up until I saw the red “out of range” marker disappear. that is when I could geusstimate what each distance was. You get used to it.

I know the red bars under your skills do signify within range for some skills.
http://wiki.guildwars2.com/wiki/Range