Map provides over all idea about an area, urban or rural. Maps may be classified according to scale, uses, purposes and others. General map classifications by scale are Large Scale (1:500-1:10,000), Medium Scale (1:20,000-1: 50,000) and Small Scale (1: 100,000-1: 2,000,000) maps.
Large Scale Maps: A detailed map of small area portraying cultural features of place names, irrigation and drainage, vegetation, settlements, roads and bridges and other infrastructure etc. Natural features related to hydro-graphy, forest, land forms with elevation information etc. Great importance is paid to their accuracy in terms of positional relationship among the features. Constructing a road, an estate, a flood-control system, or any other infrastructures require large scale maps for planning. In Survey of Bangladesh (SOB) there are different large scale maps have been produced such as Contour Maps of 16² to 1 mile (1974-77), 8² to 1 mile (1962-64) and 4² to 1 mile (1964-67), Barisal Irrigation Map (1979-86), Bangladesh map of Coastal Area of 1: 10,000 scale (prepared by FINNMAP and checked by SOB) eventually maps for greater Dhaka city and surroundings at 1: 5,000 scale etc.
Urban Sheet of scale, 1:5,000
Medium scale & Small scale: Less detailed maps of large areas show natural features of flood plains and hazards, soil erosion, climates, forest type and areas, and cultural feature of settlement pattern, population character, land use, infrastructures and income and so on. These maps are used for mostly planning purposes of strategic deployment and operation, big developmental projects and general geographical uses. For instance, a traveler wants to consult a map to set a route to destination; 1: 50,000, 1: 250,000, 1: 500,000 & 1: 1000,000 scales topographic maps of SOB are excellent tools for this purpose. Also there are other geographical maps in this category.
International Series Map of scale, 1:1,000,000
Map Classification by Function:
Topographic Maps: Natural and cultural features including elevation details are covered in a fashion of birds eye view but without perspective. These are usually prepared by government agencies in series according to scale ratio using mostly photogrammetric methods. In SOB, there are 267 sheets of 1: 50,000 scale, 27 sheets of 1: 250,000 scale, 6 sheets of 1: 500,000 scale & 4 sheets of 1: 1000,000 scale to cover entire Bangladesh. Of them 1: 500,000 scale & 1: 1000,000 scale maps are of international series. At present the base map is of 1: 50,000 scale. But SOB started preparing base map of scale 1: 25,000 and plans to complete by 2016.
Topographic Map Sheet of scale, 1:25,000
Thematic Maps: Thematic maps illustrate a particular theme or topic such as rainfall intensity or volume, land use, population density etc. The statistical information on such themes has to be obtained from different sources. Land use and land condition map of scale 1:5,000 prepared under the project “Urban Information Management for Greater Dhaka City and Surroundings” and contour map for Water Development Board are the some of the thematic maps available with SOB.
Contour Map of scale 16 inch = 1 mile
Cadastral Maps: Cadastral maps are class of thematic map though they are often classified separately showing property boundaries and areas with identification numbers and have legal significance in land registration, taxation and so on. Department of Land Records and Surveys (DLRS) is responsible for preparation of this map.
Charts: Charts are a map form adapted specially for navigation. Nautical charts for merchant navies (usually called Admiralty Charts) cover depths, currents of river or ocean along with navigational instructions and port facilities. There are charts for air navigators. Admiralty Charts and Nautical Charts (for rivers) in Bangladesh are prepared by Hydrographic Department of Bangladesh Navy and Bangladesh Inland Water Transport Authority (BIWTA) respectively. There are also charts prepared by Chittagong and Khulna Port Authorities. Aeronautical Charts for Bangladesh is prepared and printed jointly by SOB and Bangladesh Air Force.