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UTM Projection Analysis

1. UTM Coordinate System

UTM (Universal Transverse Mercator Grid System) is a Plane Rectangular Coordinate System. This system ignores the elevation information and regards the Earth's surface as an ideal ellipsoid.

2. UTM Grid Zones of the World

  • Longitude Zones: There are 60 longitudinal projection zones numbered 1 to 60 starting at 180°W. Each of these zones is 6 degrees wide. Region 1 covers the region from 180°W to 174°W, and then the region number increases eastward until Region 60, covering the region from 174°E to 180°E.
  • Latitude Zones: There are 20 latitudinal zones spanning the latitudes 80°S to 84°N and denoted by the letters C to X, ommitting the letters I and O. Each of these is 8 degrees south-north, apart from zone X which is 12 degrees south-north. N is the first north latitude zone, the letters after N belong to the north latitude zones, and the letters before N belong to the south latitude zones. It is worth noting that the polar regions further south at 80°S and further north at 84°N are not included in this system.
  • Specific UTM grid zones can refer to the link.
  • As approaching the boundary of the UTM region, the scale distortion will gradually increase. However, in practice, we often need to measure a series of positions in two adjacent areas, so it is particularly convenient and necessary to use a single grid for measurement. If necessary, we can appropriately extend the measurement results to a certain range of adjacent areas.

3. WGS84 and UTM

  • WGS84: A coordinate system used by the GPS (Global Positioning System), which uses longitude and latitude to indicate geographic location. WGS84 is a coordinate system based on the center of the Earth, that is, its origin is the centroid of the Earth.

  • UTM: This is a system that uses a 2-D Cartesian coordinate system to represent the geographical location. It divides the Earth's surface into multiple regions (except for the near-Arctic and near-Antarctic regions), each of which uses its own Plane Rectangular Coordinate System. UTM is a surface-based coordinate system, that is, its origin is a point on the surface of the Earth.

  • WGS84 is the spherical coordinates, including latitude and longitude, the unit is degree. UTM is a plane coordinate, including x- and y- coordinates, the unit is meter.

  • Conversion formula: $$Longitude\_Zone = int(\frac{Longitude}{6}) + 31$$

4. Tools and Codes