MAP NUMBERING SYSTEM

 Survey of India Map Numbering System

An International Series (within 4° N to 40°N latitude and 44° E to 124° E longitude) at the scale of 1:1000000 is being considered as a base map. The base map is divided into 4° latitude X 4° longitude and designated from 1 (at the extreme NW) to 136, covering only land areas and leaving any 4° square if it falls completely in the sea.

• For Indian maps, each section is further divided into 16 sections (4 rows and 4 columns), each 1° latitude X 1° longitude (1:250000) starting from a letter ‘A’ (NW corner) and ending on ‘P’ column-wise. These degree sheets are designated by a number and an alphabet (Such as 53M).

These degree sheets are further subdivided in the following ways:

• Each sheet is divided into four parts (2 rows & 2 columns), each of 30' latitude X 30' longitude (1:100000) designated them by cardinal directions NW, NE, SW & SE. So, such sheets are identified as 53M/SE.

• Degree sheets have also been divided into 16 sheets (4 rows by 4 columns) each 15' latitude X 15' longitude (1:50000) and numbered from 1 (at the NW corner of the particular degree sheets) to 16 column-wise and are identified as 53M/15.

• Each (1:50000) scale sheet contains four (2 rows by 2 columns) 1:25000 sheet (7.5' latitude X 7.5' longitude) which are numbered NW, NE, SW & SE. Such sheets are identified as 53M/15/NE.

Some Facts:

• Survey of India maps were based on Everest Datum and Polyconic Projection.
• Open Series Maps (OSM): They are prepared on 1:250000, 1:50000 and 1:25000 scales for the use of general public.
• OSM series maps are based on WGS-84 Datum and UTM Projections.
• Defence Series Maps (DSM) were based on WGS-84 and LCC (Lambert Conformal Conic) Projections.