Difference between a 3-degree band and a 6-degree band

 

6 degree belt:

The topographic maps of and adopt a 6-degree band projection, that is, the longitude difference is 6 degrees, starting from the zero-degree meridian, and each longitude difference of 6 degrees from west to east is a projection band, the world is divided into 60 bands, with 1, 2, 3, 4, 5 ,...... Represents. That is, the eastern longitude 0 ~ The longitude of the center longitude is 3 degrees east longitude, And the longitude is 6 degrees east longitude ~ 12 degrees is the second band, and the longitude of the central longitude is 9 degrees. Our province is located in the east longitude between 113 degrees-east longitude between 120 degrees, across 19th belts and 20 belts, of which the east longitude is 114 degrees west (including the west of Xiazhuang township in Fuping County, the wentang in Pingshan, and the west of sujiazhuang, west of the mining area, west of pulp and Water Town in Xingtai County, west of live water township in wu'an, and whole of the county) is located in 19th belts, with a central longitude of 111 degrees east and 114 degrees east to Shanhaiguan, its central meridian is 117 degrees.

3 degree band:

The-10 thousand Topographic Map adopts a 3-degree band. It starts from the longitude line of the east longitude 1.5 degrees and ranges from 1 to 2, 3 ,...... It indicates that a total of 120 projection bands are divided around the world, that is, the longitude 1.5 ~ The longitude of the central longitude is 3 degrees, and the longitude of the longitude is 4.5 ~ The longitude of the central longitude is 6 degrees east longitude. our province is located in the east longitude 113 degrees-East Longitude 120 degrees, across 38th, 39, 40 a total of 3 belts, of which the east longitude 115.5 degrees to the west is 38th, its central longitude line is east longitude 114 degrees; eastern longitude 115.5 ~ 118.5 degrees for 39 belts, the central longitude line for the east longitude is 117 degrees; 118.5 degrees for the east longitude to the west of the mountain Customs is 40, and the central longitude line for the east longitude is 120 degrees.

the first two digits of the x-axis of the kilometer network on a topographic map are the belt number. For example, the x-axis of the 20345486-Topographic Map in our province is, among them, 20 is the belt number, and 345486 is the abscissa value.
calculation of the longitude of the local central longitude line with six degrees: the longitude of the local central longitude line = 6 ° × Local longitude line-3 °, for example: the abscissa of a topographic map is 20345, And the longitude of the central longitude of the six-degree belt is 6 ° x 20-3 ° = 117 ° (applicable to and topographic maps ).
Calculation of longitude of the Three-degree central longitude line: longitude of the central longitude line = 3 ° × Local longitude belt (applicable to topographic map ).