.. index:: ! basemap .. include:: module_core_purpose.rst_ ******* basemap ******* |basemap_purpose| Synopsis -------- .. include:: common_SYN_OPTs.rst_ **gmt basemap** |-J|\ *parameters* |SYN_OPT-Rz| [ |-A|\ [*file*] ] [ |SYN_OPT-B| ] [ |-F|\ *box* ] [ |-J|\ **z**\|\ **Z**\ *parameters* ] [ |-L|\ *scalebar* ] [ |-T|\ *rose* ] [ |-T|\ *mag_rose* ] [ |SYN_OPT-U| ] [ |SYN_OPT-V| ] [ |SYN_OPT-X| ] [ |SYN_OPT-Y| ] [ |SYN_OPT-f| ] [ |SYN_OPT-p| ] [ |SYN_OPT-t| ] [ |SYN_OPT--| ] .. module_common_begins Description ----------- Creates a basic or fancy basemap (frame, with no actual map inside) with axes, fill, and titles. Several map projections are available, and the user may specify separate tick-mark intervals for boundary annotation, ticking, and (optionally) gridlines. A simple map scale (|-L|) or directional rose (|-T|) may also be plotted. At least one of the options |-B|, |-L|, or |-T| must be specified. Required Arguments ------------------ .. |Add_-J| replace:: |Add_-J_links| .. include:: explain_-J.rst_ :start-after: **Syntax** :end-before: **Description** .. |Add_-R| replace:: |Add_-R_links| .. include:: explain_-R.rst_ :start-after: **Syntax** :end-before: **Description** .. |Add_-Rz| unicode:: 0x20 .. just an invisible code .. include:: explain_-Rz.rst_ Optional Arguments ------------------ .. _-A: **-A**\ [*file*] No plotting is performed. Instead, we determine the geographical coordinates of the polygon outline for the (possibly oblique) rectangular map domain. The plot domain must be given via |-R| and |-J|, with no other options allowed. The sampling interval is controlled via :term:`MAP_LINE_STEP` parameter. The coordinates are written to *file* or to standard output if no file is specified. .. |Add_-B| replace:: |Add_-B_links| .. include:: explain_-B.rst_ :start-after: **Syntax** :end-before: **Description** .. _-F: **-F**\ [**d**\|\ **l**\|\ **t**][**+c**\ *clearances*][**+g**\ *fill*][**+i**\ [[*gap*/]\ *pen*]][**+p**\ [*pen*]]\ [**+r**\ [*radius*]][**+s**\ [[*dx*/*dy*/][*shade*]]] Without further options, draws a rectangular border around any map inset (|-D|; classic mode only), map scale (|-L|) or map rose (|-T|) using :term:`MAP_FRAME_PEN`. Used in combination with |-D|, |-L| or |-T|. Append **d** for map inset, **l** for map scale, or **t** for map rose to specify which plot embellisment the |-F| parameters should be applied to [default uses the same panel parameters for all selected map embellishments]. The following modifiers can be appended to |-F|, with additional explanation and examples provided in the :ref:`reference/features:The background panel` cookbook section: .. include:: explain_-F_box.rst_ .. _-L: .. include:: explain_-L_scale.rst_ .. _-T: .. include:: explain_-T_rose.rst_ .. |Add_-U| replace:: |Add_-U_links| .. include:: explain_-U.rst_ :start-after: **Syntax** :end-before: **Description** .. |Add_-V| replace:: |Add_-V_links| .. include:: explain_-V.rst_ :start-after: **Syntax** :end-before: **Description** .. |Add_-XY| replace:: |Add_-XY_links| .. include:: explain_-XY.rst_ :start-after: **Syntax** :end-before: **Description** .. |Add_-f| replace:: This applies only to the coordinates specified in the |-R| option. .. include:: explain_-f.rst_ .. |Add_perspective| unicode:: 0x20 .. just an invisible code .. include:: explain_perspective.rst_ .. include:: explain_-t.rst_ .. include:: explain_help.rst_ .. module_common_ends Examples -------- .. include:: oneliner_info.rst_ The following section illustrates the use of the options by giving some examples for the available map projections. Note how scales may be given in several different ways depending on the projection. Also note the use of upper case letters to specify map width instead of map scale. Non-geographical Projections ---------------------------- Linear x-y plot ~~~~~~~~~~~~~~~ To make a linear x/y frame with all axes, but with only left and bottom axes annotated, using xscale = yscale = 1cm per unit, ticking every 1 unit and annotating every 2, and using xlabel = "Distance" and ylabel = "No of samples", use :: gmt begin linear gmt basemap -R0/9/0/5 -Jx1c -Bf1a2 -Bx+lDistance -By+l"No of samples" -BWeSn gmt end show As mentioned above, such simple modern mode script can take advantage of the one-liner format. We repeat the same example using the one-liner format and then only show this format for the remaining examples: :: gmt basemap -R0/9/0/5 -Jx1c -Bf1a2 -Bx+lDistance -By+l"No of samples" -BWeSn -pdf linear Log-log plot ~~~~~~~~~~~~ To make a log-log frame with only the left and bottom axes, where the x-axis is 25 cm and annotated every 1-2-5 and the y-axis is 15 cm and annotated every power of 10 but has tick-marks every 0.1, run :: gmt basemap -R1/10000/1e20/1e25 -JX25cl/15cl -Bx2+lWavelength -Bya1pf3+lPower -BWS -pdf loglog Power axes ~~~~~~~~~~ To design an axis system to be used for a depth-sqrt(age) plot with depth positive down, ticked and annotated every 500m, and ages (in millions of years) annotated at 1 My, 4 My, 9 My etc., use :: gmt basemap -R0/100/0/5000 -Jx1cp0.5/-0.001c -Bx1p+l"Crustal age" -By500+lDepth -pdf power Polar (theta,r) plot ~~~~~~~~~~~~~~~~~~~~ For a base map for use with polar coordinates, where the radius from 0 to 1000 should correspond to 3 inch and with gridlines and ticks intervals automatically determined, use :: gmt basemap -R0/360/0/1000 -JP6i -Bafg -pdf polar Cylindrical Map Projections --------------------------- Cassini ~~~~~~~ A 10-cm-wide basemap using the Cassini projection may be obtained by :: gmt basemap -R20/50/20/35 -JC35/28/10c -Bafg -B+tCassini -pdf cassini Mercator [conformal] ~~~~~~~~~~~~~~~~~~~~ A Mercator map with scale 0.025 inch/degree along equator, and showing the length of 5000 km along the equator (centered on 1/1 inch), may be plotted as :: gmt basemap -R90/180/-50/50 -Jm0.025i -Bafg -B+tMercator -Lx1i/1i+c0+w5000k -pdf mercator Miller ~~~~~~ A global Miller cylindrical map with scale 1:200,000,000 may be plotted as :: gmt basemap -Rg -Jj180/1:200000000 -Bafg -B+tMiller -pdf miller Oblique Mercator [conformal] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To create a page-size global oblique Mercator basemap for a pole at (90,30) with gridlines every 30 degrees, run :: gmt basemap -R0/360/-70/70 -Joc0/0/90/30/0.064c -B30g30 -B+t"Oblique Mercator" -pdf oblmerc Transverse Mercator [conformal] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A regular Transverse Mercator basemap for some region may look like :: gmt basemap -R69:30/71:45/-17/-15:15 -Jt70/1:1000000 -Bafg -B+t"Survey area" -pdf transmerc Equidistant Cylindrical Projection ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This projection only needs the central meridian and scale. A 25 cm wide global basemap centered on the 130E meridian is made by :: gmt basemap -R-50/310/-90/90 -JQ130/25c -Bafg -B+t"Equidistant Cylindrical" -pdf cyl_eqdist Universal Transverse Mercator [conformal] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ To use this projection you must know the UTM zone number, which defines the central meridian. A UTM basemap for Indo-China can be plotted as :: gmt basemap -R95/5/108/20+r -Ju46/1:10000000 -Bafg -B+tUTM -pdf utm Cylindrical Equal-Area ~~~~~~~~~~~~~~~~~~~~~~ First select which of the cylindrical equal-area projections you want by deciding on the standard parallel. Here we will use 45 degrees which gives the Gall projection. A 9 inch wide global basemap centered on the Pacific is made by :: gmt basemap -Rg -JY180/45/9i -Bafg -B+tGall -pdf gall Conic Map Projections --------------------- Albers [equal-area] ~~~~~~~~~~~~~~~~~~~ A basemap for middle Europe may be created by :: gmt basemap -R0/90/25/55 -Jb45/20/32/45/0.25c -Bafg -B+t"Albers Equal-area" -pdf albers Lambert [conformal] ~~~~~~~~~~~~~~~~~~~ Another basemap for middle Europe may be created by :: gmt basemap -R0/90/25/55 -Jl45/20/32/45/0.1i -Bafg -B+t"Lambert Conformal Conic" -pdf lambertc Conic Equidistant ~~~~~~~~~~~~~~~~~ Yet another basemap of width 6 inch for middle Europe may be created by :: gmt basemap -R0/90/25/55 -JD45/20/32/45/6i -Bafg -B+t"Equidistant conic" -pdf econic Polyconic ~~~~~~~~~ A basemap for north America may be created by :: gmt basemap -R-180/-20/0/90 -JPoly/4i -Bafg -B+tPolyconic -pdf polyconic Azimuthal Map Projections ------------------------- Lambert [equal-area] ~~~~~~~~~~~~~~~~~~~~ A 15-cm-wide global view of the world from the vantage point -80/-30 will give the following basemap: :: gmt basemap -Rg -JA-80/-30/15c -Bafg -B+t"Lambert Azimuthal" -pdf lamberta Follow the instructions for stereographic projection if you want to impose rectangular boundaries on the azimuthal equal-area map but substitute |-J|\ **a** for |-J|\ **s**. Azimuthal Equidistant ~~~~~~~~~~~~~~~~~~~~~ A 15-cm-wide global map in which distances from the center (here 125/10) to any point is true can be obtained by: :: gmt basemap -Rg -JE125/10/15c -Bafg -B+tEquidistant -pdf equi Gnomonic ~~~~~~~~ A view of the world from the vantage point -100/40 out to a horizon of 60 degrees from the center can be made using the Gnomonic projection: :: gmt basemap -Rg -JF-100/40/60/6i -Bafg -B+tGnomonic -pdf gnomonic Orthographic ~~~~~~~~~~~~ A global perspective (from infinite distance) view of the world from the vantage point 125/10 will give the following 6-inch-wide basemap: :: gmt basemap -Rg -JG125/10/6i -Bafg -B+tOrthographic -pdf ortho General Perspective ~~~~~~~~~~~~~~~~~~~ The |-J|\ **G** option can be used in a more generalized form, specifying altitude above the surface, width and height of the view point, and twist and tilt. A view from 160 km above -74/41.5 with a tilt of 55 and azimuth of 210 degrees, and limiting the viewpoint to 30 degrees width and height will product a 6-inch-wide basemap: :: gmt basemap -Rg -JG-74/41.5/6i+z160+a210+t55+v30 -Bafg -B+t"General Perspective" -pdf genper Stereographic [conformal] ~~~~~~~~~~~~~~~~~~~~~~~~~ To make a polar stereographic projection basemap with radius = 12 cm to -60 degree latitude, with plot title "Salinity measurements", using 5 degrees annotation/tick interval and 1 degree gridlines, run :: gmt basemap -R-45/45/-90/-60 -Js0/-90/12c/-60 -B5g1 -B+t"Salinity measurements" -pdf stereo1 To make a 12-cm-wide stereographic basemap for Australia from an arbitrary view point (not the poles), and use a rectangular boundary, we must give the pole for the new projection and use the |-R| option to indicate the lower left and upper right corners (in lon/lat) that will define our rectangle. We choose a pole at 130/-30 and use 100/-45 and 160/-5 as our corners. The command becomes :: gmt basemap -R100/-45/160/-5+r -JS130/-30/12c -Bafg -B+t"General Stereographic View" -pdf stereo2 Miscellaneous Map Projections ----------------------------- Hammer [equal-area] ~~~~~~~~~~~~~~~~~~~ The Hammer projection is mostly used for global maps and thus the spherical form is used. To get a world map centered on Greenwich at a scale of 1:200000000, use :: gmt basemap -Rd -Jh0/1:200000000 -Bafg -B+tHammer -pdf hammer Sinusoidal [equal-area] ~~~~~~~~~~~~~~~~~~~~~~~ To make a sinusoidal world map centered on Greenwich, with a scale along the equator of 0.02 inch/degree, use :: gmt basemap -Rd -Ji0/0.02i -Bafg -B+tSinusoidal -pdf sinus1 To make an interrupted sinusoidal world map with breaks at 160W, 20W, and 60E, with a scale along the equator of 0.02 inch/degree, run the following sequence of commands: :: gmt begin gmt basemap -R-160/-20/-90/90 -Ji-90/0.02i -Bx30g30 -By15g15 -BWesn gmt basemap -Bx30g30 -By15g15 -Bwesn -X2.8i gmt basemap -Bx30g30 -By15g15 -BwEsn -X1.6i gmt end show Eckert IV [equal-area] ~~~~~~~~~~~~~~~~~~~~~~ Pseudo-cylindrical projection typically used for global maps only. Set the central longitude and scale, e.g., :: gmt basemap -Rg -Jkf180/0.064c -Bafg -B+t"Eckert IV" -pdf eckert4 Eckert VI [equal-area] ~~~~~~~~~~~~~~~~~~~~~~ Another pseudo-cylindrical projection typically used for global maps only. Set the central longitude and scale, e.g., :: gmt basemap -Rg -Jks180/0.064c -Bafg -B+t"Eckert VI" -pdf eckert6 Robinson ~~~~~~~~ Projection designed to make global maps "look right". Set the central longitude and width, e.g., :: gmt basemap -Rd -JN0/8i -Bafg -B+tRobinson -pdf robinson Winkel Tripel ~~~~~~~~~~~~~ Yet another projection typically used for global maps only. You can set the central longitude, e.g., :: gmt basemap -R90/450/-90/90 -JR270/25c -Bafg -B+t"Winkel Tripel" -pdf winkel Mollweide [equal-area] ~~~~~~~~~~~~~~~~~~~~~~ The Mollweide projection is also mostly used for global maps and thus the spherical form is used. To get a 25-cm-wide world map centered on the Dateline: :: gmt basemap -Rg -JW180/25c -Bafg -B+tMollweide -pdf mollweide Van der Grinten ~~~~~~~~~~~~~~~ The Van der Grinten projection is also mostly used for global maps and thus the spherical form is used. To get a 18-cm-wide world map centered on the Dateline: :: gmt basemap -Rg -JV180/18c -Bafg -B+t"Van der Grinten" -pdf grinten Arbitrary rotation ~~~~~~~~~~~~~~~~~~ If you need to plot a map but have it rotated about a vertical axis then use the **-p** option. For instance, to rotate the basemap below 90 degrees about an axis centered on the map, try :: gmt basemap -R10/40/10/40 -JM10c -Bafg -B+t"I am rotated" -p90+w25/25 -Xc -pdf rotated .. module_note_begins Custom Labels or Intervals -------------------------- The |-B| option sets up a regular annotation interval and the annotations derive from the corresponding *x*, *y*, or *z* coordinates. However, some applications require special control on which annotations to plot and even replace the annotation with other labels. This is achieved by using **c**\ *intfile* in the |-B| option, where *intfile* contains all the information about annotations, ticks, and even gridlines. Each record is of the form *coord* *type* [*label*], where *coord* is the coordinate for this annotation (or tick or gridline), *type* is one or more letters from **a** (annotation), **i** interval annotation, **f** tickmark, and **g** gridline. Note that **a** and **i** are mutually exclusive and cannot both appear in the same *intfile*. Both **a** and **i** require you to supply a *label* which is used as the plot annotation. If not given then a regular formatted annotation based on the coordinate will occur. Restrictions ------------ For some projections, a spherical earth is implicitly assumed. A warning will notify the user if |-V| is set. Bugs ---- The |-B| option is somewhat complicated to explain and comprehend. However, it is fairly simple for most applications (see examples). .. module_note_ends See Also -------- :doc:`gmt`, :doc:`gmt.conf`, :doc:`gmtcolors`