Metal Detecting Research and Exploration - A Complete Guide, page 24
Understanding Map Scales
SCALES OF MODERN TOPOGRAPHIC MAPS
All countries in the Eastern Europe use a metric system, that is why the scales of modern topographical maps are expressed in meters (m) or kilometers (km) to 1 centimeter (cm):
Scale: 1:10,000
This is the ultra large map scale. The map of this scale is the most detailed map showing 100 meters of the ground surface in 1cm on the map. The large sheets of this scale maps are not available to the public and used primarily by the geodesists - land surveyors. These maps are used as extracts showing town and city centers on the smaller scale maps.
Scale 1:24,000 (240 meters to 1cm)
This is the only non-metric scale used on the United States Geological Survey (USGS) topographic maps of the 7.5-minute series (described on page 5). The USGS 7.5' topographic map series cover only the United States. This maps are excellent for metal detecting research, and as The National Map program speeds up, more large-scaled topo maps will be readily available to the public on the Internet for free.
Scale: 1:25,000 (250 meters to 1cm)
Maps at this scale are also very detailed and extremely helpful for treasure hunting research. The USGS 7.5' metric series at this scale are available. The new 1:20,000 (200 meters to 1cm) series is gradually replacing the old 1:25,000 series.
Scale: 1:50,000 (500 meters to 1cm)
The maps of this large scale are the most used maps for treasure hunting map research because this scale is almost equal to the scales of the 17th, 18th and 19th centuries large-scaled maps.
This equality of scales makes it easy for treasure hunters to georeference many old maps for GPS navigation. These maps contain various contours in intervals of 25 feet or 10 meters. A 1:50,000 scale topo map is one of the 16 segments of the 1:250,000 scale map.
Scale: 1:100,000
The maps of scale 1:100,000 (1 km to 1 cm, or 1 inch equals to approximately 1.5 miles) still can be used for research, however they carry less detail and have contour interval of 20 meters. Treasure hunters use this scale maps only when the maps of scale 1:50000 are not available for the area in focus.
Scale: 1:200,000 (2 km to 1 cm)
The maps of this scale are not useful for metal detecting research due to the lack of important detail. These maps can be used for reference.
Scale: 1:250,000 (2.5 km to 1 cm)
These maps have various contours intervals of 100 feet and 20 or 50 meters and are popular for providing a good overall view of a large area - ideal for traveling on back roads; not useful for treasure hunting map research. Coverage Area per Map: approximately 16,000 square kilometers.
The maps of scales 1:500,000 (1 cm to 5km), 1:1000,000 (1 cm to 10 km) and 1:2,000,000 (20 km in 1 cm) are good only for indexing the large scale maps, and, maybe, general navigation. These maps cover large squares of land per page.