The Russian Military secretly mapped the entire world, but few outsiders have seen the maps—until now.

A manual produced by the Russian Army, translated and published in 2005 by East View, a Minnesota company with a large inventory of Soviet maps, gives some insight into how the topographic maps could be used in planning or executing combat operations. It includes tables on the range of audibility of various sounds (a snapping twig can be heard up to 80 meters away; troop movements on foot, up to 300 meters on a dirt road or 600 meters on a highway; an idling tank, up to 1,000 meters; a rifle shot, up to 4,000 meters).

Other tables give the distances for visual objects (a lit cigarette can be visible up to 8,000 meters away at night, but you’d have to get within 100 meters to make out details of a soldier’s weaponry in daylight). Still more tables estimate the speed at which troops can move depending on the slope of the terrain, the width and condition of the roadway, and whether they are on foot, in trucks, or in tanks.

The maps themselves include copious text with detailed descriptions of the area they depict, everything from the materials and conditions of the roads to the diameter and spacing of the trees in a forest to the typical weather at different times of year. The map for Altan Emel, a remote region of China near the border of Mongolia and Russia, includes these details, according to a translation on Omnimap’s website:

Inside the crates were maps, thousands of them. In the top right corner of each one, printed in red, was the Russian word секрет. Secret.

The maps were part of one of the most ambitious cartographic enterprises ever undertaken. During the Cold War, the Soviet military mapped the entire world, parts of it down to the level of individual buildings. The Soviet maps of US and European cities have details that aren’t on domestic maps made around the same time, things like the precise width of roads, the load-bearing capacity of bridges, and the types of factories. They’re the kinds of things that would come in handy if you’re planning a tank invasion. Or an occupation. Things that would be virtually impossible to find out without eyes on the ground.

Given the technology of the time, the Soviet maps are incredibly accurate. Even today, the US State Department uses them (among other sources) to place international boundary lines on official government maps.

Read More: Wired

Featured Image – The image shows an area in the northern part of Russia’s Sakha Republic in eastern Siberia. The Olenek River winds northeast from the bottom of the images to the upper left, and the delta through which the mighty Lena River empties into the Laptev Sea dominate the top portions of the images. DVIDS.

Featured Media- USGS, Dated yet Compromised Russia, Geospatial, Wired