Weapon Accuracy Score
Tracking in EVE is measured by a turret attribute called Weapon Accuracy Score or WAS for short. It is an attribute that unifies the tracking value for all weapons, regardless the size of the weapons (larger weapons have a harder time hitting smaller targets).
Easy to compare relative tracking of weapons
Since tracking is uniformly calculated across different types and sizes, you can easily compare one gun to another. Here's an example:
|Type of weapon||Size||WAS|
Legacy tracking attributes
While all usable turrets ingame have been changed to present Weapon Accuracy Score, a lot of things like NPCs and drones still use the old legacy term Signature Resolution and Tracking Speed.
This is an old attribute that lists the relative signature of the target the weapon, drone or NPC is intended to be fired upon. This Signature Resolution is measured the same as the ship attribute Signature Radius:
|Signature||Intended target||Examples that use this resolution|
|2 000 m||Capital-class targets||NPC capitals (X-Large turrets )|
|400 m||Battleship-class targets||Heavy drones, sentry drones, NPC battleships (large turrets )|
|125 m||Cruiser-class targets||Medium drones, NPC cruisers (medium turrets )|
|40 m||Frigate-class targets||Light drones, NPC frigates (small turrets )|
The old Tracking Speed attribute didn't used to take into consideration your Signature Resolution, so a large weapon could have a similar tracking speed value of a smaller gun, making them seem, at first glance, to have equally good tracking. In short it was simply the tracking value in and by itself, not accounting for the size of the gun (its resolution) and how that would lower the practical tracking.
If you want to see how well drones or NPCs track, compared to your own weapons, you can reverse-engineer the value like this:
|Weapon Accuracy Score = Tracking Speed * 40000 / Signature Resolution|
Similarly you can find out the old tracking value from a weapon accuracy score like this:
|Tracking Speed = Weapon Accuracy Score / 40000 * Signature Resolution|