Topographical sheet numbering
Also called: Toposheet index · Topic: Topographical Maps: Relief Representation and Interpretation · NCERT: Class 11, Ch 5 "Topographical Maps"
Meaning
Topographical sheet numbering is the Survey of India's system for naming each map sheet so that it can be found easily. A 4° × 4° sheet at 1:1,000,000 gets a number, such as 63. It is split into 16 sheets of 1° × 1° at 1:250,000, lettered A to P (such as 63K). Each of these is split again into 16 sheets of 15' × 15' at 1:50,000, numbered 1 to 16 (such as 63K/12). So one degree sheet holds 16 fifty-thousand sheets, and one million sheet holds 256.
Example
Sheet 63K/12 is a 1:50,000 sheet that covers parts of Mirzapur and Varanasi districts in Uttar Pradesh, on the Ganga. Its name tells you it is part 12 of degree sheet 63K, which is itself part K of million sheet 63.
Don't confuse with
- Lettering and numbering: letters (A–P) mark the 1:250,000 degree sheets. Numbers (1–16) mark the 1:50,000 sheets. Both levels split into 16 parts, but they are labelled in different ways.