Surveying ME - BMEEOAFM201

The Earth has a special figure, which can be modelled using a sphere or an ellipsoid of revolution. In the engineering practice, you need a coordinate system in a horizontal plane, hence you have to flatten the globe's surface into a plane. This kind of conversion can be done using either simple geometry or mathematical formulas. That is the science of map projections.

The three main types of map projections:

• azimuthal
• cylindrical
  
• conic

Important map projections

1. Web Mercator
2. UTM
3. Hungarian EOV

Web Mercator

• used by all major web map providers: Google, Bing, OSM ...
• simple formulas and calculation
• meridians are equally spaced vertical lines
  
• applicable for global and local areas as well
• relatively large distortions, especially near the poles

source: https://www.atlasandboots.com/map-projections/#gallery-7

UTM: Universal Transverse Mercator

• 60 zones, each of them has 6 degrees of longitude in width
• the cylinder intersects the ellipsoid, the scale factor at the central meridian is 0.9996
• false easting and northing
• WGS84 ellipsoid
• NATO's official map projection 
• one map projection for the whole globe with relatively small distortions
• a wide range of countries applies as a national map projection

source: https://gisgeography.com/wp-content/uploads/2016/05/UTM-Zones-Globe-2-300x291.png

source: https://www.nrcan.gc.ca/earth-sciences/geography/topographic-information/maps/utm-grid-map-projections/utm-grid-universal-transverse-mercator-projection/9779

Hungarian EOV

• established in the 1970s
• defined for large scale maps, distortion should be under 1/10000 (actually in 90 % of Hungary is fulfilled)
• local ellipsoid of revolution

source: https://www.tankonyvtar.hu/hu/tartalom/tamop425/0027_DAI1/ch01s04.html