The blast door map, first seen in the 17th episode of Season 2, "Lockdown", is a map of DHARMA Initiative facilities on the Island discovered by Locke at the Swan. The map and its accompanying annotions were drawn on one of the blast doors in paint that would fluoresce under ultraviolet light. The map was only visible briefly during the lockdown incident and was later destroyed in the Swan implosion.
Stuart Radzinsky, a DHARMA Initiative member and architect of the Swan station, originally created the map. He and his partner, Kelvin Inman regularly forced a lockdown sequence to engage the blast doors to continue their work on the map. The map's creators were forced to work blindly as the map could only be seen under conditions when the Swan was illuminated with black-light. Following Radzinsky's suicide, Kelvin continued working on the map, albeit at a much slower pace. Kelvin described Radzinsky as having a photographic memory, allowing him to remember exactly where he left off. It is unknown if Desmond ever contributed to the map. ("Live Together, Die Alone")
DHARMA laundry detergent was at least one of the substances used as "paint" on the map. Likely other mixtures were used to create the different colours.
In the semi-canon video game, Via Domus, there are two spectrum levels of the map which can be seen under different lighting conditions. The first was as seen by Locke. The second spectrum of the map includes more geographical locations and notations. ("Forty-Two")
There are numerous handwritten notations across the blast door map. There were at least two types of notations on the map: printed notes in English, informed and factual; and more speculative philosophical musings in Latin written in cursive. Likely a combination of information and guesswork on the part of its creators, the map does not appear to be entirely accurate.
The hidden map shows the location of six stations with a seventh crossed out. All the stations appear to be pointing towards the center of the Island, represented on the map by a large question mark. Four of the stations appear with names and logos: the Arrow, the Staff, the Flame and the Swan. The central location, indicated by the question mark at the center of the map was later identified as the Pearl. ("?")
The notes are written in several scripts, suggesting multiple contributors. The notes can be grouped into four general categories: English commentary, Latin commentary, mathematical equations and object labels (the Swan, the Flame, CVIII, etc). The Latin phrases appear to be more of a running commentary than insightful notations about the map. By contrast, the majority of the notations written in English address the various stations, references to an incident, possible shutdowns, a Cerberus system, the Periodic Resupply Drop and a DharmaTel network.
Found on the blast door map are several equations, both mathematical and scientific, written as additional notations to the diagram. Three trigonometric equations are located in the top left-hand corner of the blast door map, two calculus problems appear to be engineering/physics equations related to magnetism, two derived values are found at the far right of the map, and other various mathematical equations are spread throughout it.
There are several notations on the hidden map that appear to be dates, which use a month/day/year format. Some appear to indicate a the timestamp when a "shutdown" occurred. What was shut down and why are unknown. There is another date reference to a zoological research facility and a reference to something called an AH/MDG incident of 1985.
The Via Domus version of the map seen by Elliott Maslow in "Forty-Two", is a canonical addition to the blast door map, since the producers stated that there is another version of the map seen under a different light. (Access: Granted)
A summary of the additions to this map, listed counter-clockwise:
In addition to the screen capture of the map from "Lockdown", the original map has been presented through other official venues. These images were apparently taken from the original prop source, and thus are higher quality images, some of which show more details and sections of the map than those from the episode itself. These include:
Locke was the only one of the survivors to see the blast door map and later tried to recreate the map on paper by drawing what he recalled. Only seeing the map for a few seconds, his memory is somewhat sketchy, but he appeared to recall the general station locations, the 'rivers' and the question mark in the center of the map. After various attempts, Locke eventually drew a good copy which he eventually gave to Mr. Eko. ("S.O.S.") ("?")