Some space launches are carried out from mobile structures which don't have a fixed geographical location. I thus distinguish between the `platform' (the vehicle used as a launch platform) and the `site' (the geographical location at which the platform was located when the rocket separated from it).
Platforms which have been used to launch rockets include surface ships, submarines and aircraft. (I also include the KSC pad 39 mobile launch platforms, just because I want to record which one was used for which launch and it's a useful database field to stash that particular information.)
I consider ship launches to fall into two main categories: individual launches from launch zones (LZ) and launches on cruises (LC). In a cruise, a specific ship launches a series of rockets at different (sometimes widely different) geographical locations (launch points). Conceptually I think of the cruise path as a launch site and the launch points as different launch pads in that site. However, some launch points were used many times by different ships and cruises. These frequently used launch locations (e.g. OJP, in the Pacific at 160E 0N) are instead defined as a launch zone. Therefore, a cruise can consist of launches associated with the cruise's own site (LC) value and also with one or more standard LZs. For example, the Akademik Korolev (KORO) made a cruise in Feb-Mar 1973 (cruise GMS73A) which had launches from launch points LP1 to LP8 associated with site value GMS73A as well as launches from frequently-visited Indian Ocean sites IO65, IOCOR, RODR, IOSWR and IO6540. I recognize that this is a bit messy but I think making explicit that these sites are used by multiple ships and cruises is helpful.
The fields in the Platforms data file are
Null values are indicated by a dash or an asterisk. Null TStart means the start date of the organization is unknown; Null Stop means that the organization is still in operation, or assumed to be so.
The error field gives the uncertainty of the launch site location. Note that when a launch site contains multiple launch pads or launch points, the position given for the site is a bit arbitrary, and you should consult the LP (launch points) database for precise positions.