Concept definition: |
The identification of a specific geotile within the Geotile Reference System (GTRS) formatted in a Basic Latin string. The string contains a 6-digit alphanumeric designation, the first two letters of which are the encompassing GTRS megatile, the next two digits are the easting index of the geotile within the megatile, and the last two digits are the northing index of the geotile within the megatile. The 2 letter designation of the GTRS megatile is based on the location of its south-west corner and is composed of a letter designating the longitudinal position of the megatile followed by a letter designating the latitudinal position of the megatile. Between 60° N and 60° S there are 24 longitudinal zones of megatiles each of 15 arc degrees width beginning at 180° W and extending eastward through 360 arc degrees of longitude. These zones are lettered from A to Z inclusive (omitting I and O). Between 60° N and 90° N and between 60° S and 90° S there are 12 longitudinal zones of megatiles each of 30 arc degrees width beginning at 180° W and extending eastward through 360 arc degrees of longitude. These zones are lettered as A, C, E, G, J, L, N, Q, S, U, W and Y. There are 12 latitudinal bands of megatiles each of 15 arc degrees height, beginning at 90° S and extending northward through 180 arc degrees of latitude. These are lettered from A to M inclusive (omitting I). This 2 letter designation thus divides the earth's surface into 288 GTRS megatiles. The index of a GTRS geotile within a GTRS megatile is based on the location of its south-west corner and is composed of two digits designating the relative longitudinal position of the geotile followed by two digits designating the relative latitudinal position of the geotile. Between 60° N and 60° S there are 15 longitudinal zones of geotiles within a megatile, each of 1 arc degree width extending eastward from the western edge of the megatile. These zones are numbered from 00 to 14 inclusive. Between 60° and 71° (N or S) there are 15 longitudinal zones of geotiles within a megatile, each of 2 arc degrees width extending eastward from the western edge of the megatile. These zones are even numbered from 00 to 28 inclusive. Between 71° and 78° (N or S) there are 10 longitudinal zones of geotiles within a megatile, each of 3 arc degrees width extending eastward from the western edge of the megatile. These zones are numbered 00, 03, 06, 09, 12, 15, 18, 21, 24 and 27. Between 78° and 80° (N or S) there are 6 longitudinal zones of geotiles within a megatile, each of 5 arc degrees width extending eastward from the western edge of the megatile. These zones are numbered 00, 05, 10, 15, 20 and 25. Between 80° and 84° (N or S) there are 5 longitudinal zones of geotiles within a megatile, each of 6 arc degrees width extending eastward from the western edge of the megatile. These zones are numbered 00, 06, 12, 18 and 24. Between 84° and 86° (N or S) there are 3 longitudinal zones of geotiles within a megatile, each of 10 arc degrees width extending eastward from the western edge of the megatile. These zones are numbered 00, 10 and 20. Between 86° and 88° (N or S) there are 2 longitudinal zones of geotiles within a megatile, each of 15 arc degrees width extending eastward from the western edge of the megatile. These zones are numbered 00 and 15. Between 88° and 90° (N or S) there is a single longitudinal zone of geotiles within a megatile of 30 arc degrees. This zone is numbered 00. There are 15 latitudinal bands of geotiles within a megatile, each of 1 arc degree height, extending northward from the southern edge of the megatile. These bands are numbered from 00 to 14 inclusive. This 2 letter designation thus divides a GTRS megatile into as many as 225 GTRS geotiles. EXAMPLE The location 24° N 37° E corresponds to the south-west corner of the GTRS geotile designated "QH0709". |