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# 5. GMT Projections

GMT programs that read position data will need to know how to convert the input coordinates to positions on the map. This is achieved by selecting one of several projections. The purpose of this section is to summarize the properties of map projections available in GMT, what parameters define them, and demonstrate how they are used to create simple basemaps. We will mostly be using the pscoast command and occasionally psxy. (Our illustrations may differ from yours because of different settings in our .gmtdefaults file.) Note that while we will specify dimensions in inches (by appending i), you may want to use cm (c), meters (m), or points (p) as unit instead (see gmtdefaults man page).

Subsections

- 5.1 Non-map Projections
  - 5.1.1 Cartesian Linear Projection (-Jx -JX)
  - 5.1.2 Logarithmic projection
  - 5.1.3 Power projection
  - 5.1.4 Geographical linear projection
  - 5.1.5 Linear Projection with Polar () Coordinates (-Jp -JP)
- 5.2 Conic Projections
  - 5.2.1 Albers Conic Equal-Area Projection (-Jb -JB)
  - 5.2.2 Lambert Conic Conformal Projection (-Jl -JL)
  - 5.2.3 Equidistant Conic Projection (-Jd -JD)
- 5.3 Azimuthal Projections
  - 5.3.1 Lambert Azimuthal Equal-Area (-Ja -JA)
    - 5.3.1.1 Rectangular map
    - 5.3.1.2 Hemisphere map
  - 5.3.2 Stereographic Equal-Angle Projection (-Js -JS)
    - 5.3.2.1 Polar Stereographic Map
    - 5.3.2.2 Rectangular Stereographic Map
    - 5.3.2.3 General Stereographic Map
  - 5.3.3 Orthographic Projection (-Jg -JG)
  - 5.3.4 Azimuthal Equidistant Projection (-Je -JE)
  - 5.3.5 Gnomonic Projection (-Jf -JF)
- 5.4 Cylindrical Projections
  - 5.4.1 Mercator Projection (-Jm -JM)
  - 5.4.2 Transverse Mercator (-Jt -JT)
  - 5.4.3 Universal Transverse Mercator UTM (-Ju -JU)
  - 5.4.4 Oblique Mercator (-Jo -JO)
  - 5.4.5 Cassini Cylindrical Projection (-Jc -JC)
  - 5.4.6 Cylindrical Equidistant Projection (-Jq -JQ)
  - 5.4.7 General Cylindrical Projections (-Jy -JY)
  - 5.4.8 Miller Cylindrical Projections (-Jj -JJ)
- 5.5 Miscellaneous Projections
  - 5.5.1 Hammer Projection (-Jh -JH)
  - 5.5.2 Mollweide Projection (-Jw -JW)
  - 5.5.3 Winkel Tripel Projection (-Jr -JR)
  - 5.5.4 Robinson Projection (-Jn -JN)
  - 5.5.5 Eckert IV and VI Projection (-Jk -JK)
  - 5.5.6 Sinusoidal Projection (-Ji -JI)
  - 5.5.7 Van der Grinten Projection (-Jv -JV)