Question

List the aspects that you should keep in mind while studying a topographical map.

Name some elements of a topo sheet or topographical maps.

Answer 1

Some of the elements of a topo sheet are:

1. Sheet number — This number refers to a specific geographical area. It is written on the top of the sheet.
2. Scale — The scale is not the same for all maps. It can be 1 : 10,00,000 1 cm : 10 km], 1 : 250,000 [i.e. ; 1 cm = 2.5 km] or 1 : 50,000 [i.e. 2 cm = 1 km] It is written at the bottom of the sheet.
3. Grid — The sheets have grid lines in red called eastings and northings which help in locating places easily.
4. Direction on map sheet — The top half of a topographical map is always the north and the bottom half is the south. The right hand is the east and left hand is the west. The eastings and northings are read from the southwest corner.
5. The eastings and northings — Their numbers should be remembered before reading a map.
6. Four-figure grid reference and six-figure grid reference squares — The four-figure grid reference will have four digits and six-figure grid reference will have six digits.
7. Legend and keys — Legends contain conventional signs and symbols in the form of keys. They provide the vital information to interpret the map correctly.
8. Contour interval — (Vertical interval) It is the vertical distance between two consecutive contour lines. It remains same for a given scale of topo sheets.
9. Spot heights — These indicate the actual elevation of a spot above mean sea level.
10. Triangulated stations — These also indicate the height on maps. They are indicated on the map with a small triangle followed by the number.
11. Contour index — Every fifth contour line is bolder than the other lines for easy identification of contour lines.
12. Places marked with letters DEP (depression) indicate land at a lower level than the surrounding area.
13. Dry and wet streams — On the map, black streams are dry and blue streams have water.
14. Contour features — Like saddle, hill, pass, gentle and steep slope, ridge, etc can be seen on topo maps.
15. Colours — Green coloured area contains vegetation and forests, yellow coloured area is cultivated land and white portion is barren land.