Open Series Maps

Also called: OSM · Topic: Topographical Maps: Relief Representation and Interpretation · NCERT: Beyond NCERT

Meaning

Open Series Maps (OSMs) are the Survey of India (SoI) topographic maps for public, civil use. They were created under the National Map Policy 2005, are drawn on the WGS-84 datum and UTM projection, and become "Unrestricted" after a one-time clearance from the Ministry of Defence (MoD). Sensitive sites are removed from them [1].

They matter because planners need detailed maps of relief, rivers and roads to build dams, roads and cities. OSMs give them this detail without exposing military secrets.

Explanation

Why OSMs were created

• The problem: one map, two needs
• Planners need detailed maps for roads, dams, cities and relief work after disasters.

• The same detail, such as exact heights or military sites, can harm national security if anyone can get it.

• The answer: National Map Policy 2005

• It split SoI topographic maps into two series, Defence Series Maps (DSMs) and Open Series Maps (OSMs). The aim was to keep the country safe and still open up map data for development [1].
• Both series come from one master database, the National Topographical Database (NTDB) [1].

• NTDB has five data sets: National Spatial Reference Frame, National Digital Elevation Model, National Topographical Template, Administrative Boundaries and Toponymy (place names) [1].

• Who makes them: OSMs are made only by SoI, India's National Mapping Agency. SoI works under the Department of Science and Technology (DST). OSMs are mainly meant to support development work across the country [1].

Technical base: datum, projection and sheet numbers

• Datum (a model of the Earth's shape that latitudes, longitudes and heights are measured against):
• OSMs use only WGS-84 (World Geodetic System 1984) [1]. This is a global datum.
• GPS also uses WGS-84, so OSMs match GPS and satellite data directly.

• India's old Everest datum fits the Indian subcontinent well but not the rest of the world. OSMs do not use it.

• Projection (a way of drawing the curved Earth on a flat sheet):

• OSMs use only UTM (Universal Transverse Mercator) [1]. UTM is a global grid that splits the world into 60 zones, each 6° of longitude wide.

• The older Polyconic projection is not used on OSMs.

• Sheet numbers: OSMs have different sheet numbers from DSMs [1]. This means an OSM sheet cannot be matched one-to-one with a DSM sheet by its number.

How security is protected

• One-time MoD clearance:

• Each OSM, on paper or digital, needs a one-time clearance from MoD. After that it becomes "Unrestricted" [1].

• No VAs/VPs:

• Vulnerable Areas and Vulnerable Points (VAs/VPs) are sensitive civil and military sites, such as defence bases and key installations.

• SoI makes sure no VAs/VPs appear on OSMs [1].

• Relief removed only in restricted zones:

• Contours and heights are left out in restricted zones, as MoD instructs [1].
• Everywhere else, OSMs show full relief.

What an OSM shows, and how people get it

• Content still shown [1]:
• Margin details: lat/long, sheet number, year of survey, magnetic variation and the Representative Fraction (RF) (the scale written as a ratio, such as 1:50,000)
• Administrative boundaries, from the international boundary down to the village, including boundary pillars and village trijunctions
• All roads, tracks, passes, railways and tunnels
• All streams, canals, earthwork dams, wells, springs and tanks
• Settlements, forts, religious places and police stations
• Transmission lines
• Relief: contours, sand features, ice forms, spot heights and benchmarks (surveyed points of exact height)

• Vegetation, and reserved or protected forests

• Access:

• OSMs at scales larger than 1:1 million can be sold, or given under an agreement for a stated end use [1].
• Each deal is recorded in a Map Transaction Registry [1].
• At first, buyers signed an undertaking (a written promise about how they would use the map).

• Today, OSMs can be downloaded from SoI's online maps portal.

• Value addition:

• Users may add their own data to OSMs and publish them on paper or on the web, with or without a GIS database [1].
• A map that shows the international boundary needs SoI certification [1].

Where it occurs

• Coverage: OSMs cover the whole of India. They are made by Survey of India under DST, under the National Map Policy 2005 [1].
• Restricted zones: Contours and heights are removed only in zones marked as restricted by MoD [1]. These are often the border Himalayan districts.
• How OSMs and their relief data are used in India:
• Watershed and irrigation planning:
  • Contours show where water flows and where ridges divide catchments (the area drained by one stream).
  • Planners use this to place check dams, tanks and canals.
• Road and rail alignment:
  • Closely spaced contours mean a steep slope. Widely spaced contours mean a gentle slope.
  • Engineers use this to pick gentle gradients, plan cuttings and tunnels, and avoid steep or unstable ground.

• Disaster risk mapping in the Himalaya:

  • Slope, relief and drainage from the sheets help mark areas at risk of landslides, floods and glacial lake outbursts.

• Related public maps: SoI also makes large-scale City Maps on WGS-84. These are in the public domain, and their content is decided with MoD [1].

• Later opening of map data:
• Geospatial Guidelines, 15 February 2021 (DST): Indian entities need no prior approval, security clearance or licence to collect, make, store, publish or digitise geospatial data and maps within India [2][3].
• National Geospatial Policy 2022: geospatial data made with public funds should be openly available [4][5].

Don't confuse with

• Defence Series Maps (DSMs): DSMs have full content and full accuracy, may use the Everest or WGS-84 datum on Polyconic or UTM projection, and are classified under MoD rules. OSMs use WGS-84 + UTM only and are "Unrestricted" [1].
• Old SoI toposheets (Everest/Polyconic): the older sheets used the Everest datum and Polyconic projection. OSMs moved to the global WGS-84/UTM system and have separate sheet numbers [1].
• Geospatial Guidelines 2021: these are not a map series. They are rules that removed the need for prior approval and kept only a negative list of sensitive attributes (features that cannot be marked on any map). There is no negative list of areas [2][3]. OSMs instead need a one-time MoD clearance for each sheet [1].
• City Maps: these are also public SoI maps on WGS-84, but they are large-scale maps of towns whose content is decided with MoD. They are not part of the OSM topographic sheet series [1].

Prelims Hooks

• The National Map Policy 2005 created two series: Defence Series Maps and Open Series Maps [1].
• OSMs are on WGS-84 datum + UTM projection only. DSMs may be on Everest/WGS-84 and Polyconic/UTM [1].
• Each OSM becomes "Unrestricted" after a one-time clearance by the Ministry of Defence, not by SoI or DST [1].
• Trap: OSMs do show contours, spot heights and benchmarks. Contours and heights are removed only in restricted zones [1].
• OSMs at scales larger than 1:1 million can be sold or given under an end-use agreement. Each deal is recorded in a Map Transaction Registry [1].
• A value-added map that shows the international boundary needs SoI certification [1].

Mains Points

• Security vs development (GS-I/III):
• The 2005 two-series policy keeps secret military detail in DSMs and gives cleaned civil maps (OSMs) to planners. Both come from the same NTDB [1].
• This lets roads, dams, irrigation and city planning go ahead without exposing VAs/VPs.

• The cost: contours and heights are missing in restricted zones. These are often the border Himalayan districts, where landslide and flood planning needs relief data the most.

• From control to openness (GS-III, infrastructure):

• OSMs were the first step. Moving to WGS-84/UTM let Indian maps match GPS and satellite data, and users could add their own GIS layers [1].
• The 2021 Guidelines replaced "permission first" with a short negative list of attributes [2][3]. NGP 2022 made publicly funded geospatial data openly available [4][5].

• Together they cut project delays and help Indian mapping firms compete globally [2].

• Disaster and rural planning (GS-III):

• Contours and drainage on OSMs help mark landslide, flood and glacial lake outburst risk in the Himalaya.
• They also support watershed works such as check dams, tanks and canals, and help choose gentle routes for hill roads and railways.

Related concepts

• Defence Series Maps

Read more

• Open Series and Defence Series Maps today