.TH MAPPROJECT 1gmt "15 Jul 2011" "GMT 4.5.7" "Generic Mapping Tools"
.SH NAME
mapproject \- Forward and Inverse map transformation of 2-D coordinates 
.SH SYNOPSIS
\fBmapproject\fP \fIinfiles\fP \fB\-J\fP\fIparameters\fP \fB\-R\fP\fIwest\fP/\fIeast\fP/\fIsouth\fP/\fInorth\fP[\fBr\fP] 
[ \fB\-Ab\fP|\fBB\fP|\fBf\fP|\fBF\fP[\fIlon0\fP/\fIlat0\fP] ] [ \fB\-C\fP[\fIdx\fP/\fIdy\fP] ] [ \fB\-Dc\fP|\fBi\fP|\fBm\fP|\fBp\fP ] [ \fB\-E\fP[\fIdatum\fP] ] 
[ \fB\-F\fP[\fBk\fP|\fBm\fP|\fBn\fP|\fBi\fP|\fBc\fP|\fBp\fP] ] [ \fB\-G\fP[\fIx0\fP/\fIy0\fP][\fB+\fP|\fB-\fP][/\fIunit\fP] ] [ \fB\-H\fP[\fBi\fP][\fInrec\fP] ] [ \fB\-I\fP ] 
[ \fB\-L\fP\fIline.xy\fP[/\fIunit\fP][\fB+\fP] ] [ \fB\-Q\fP[\fBd\fP|\fBe\fP ] [ \fB\-S\fP ] [ \fB\-T\fP[\fBh\fP]\fIfrom\fP[/\fIto\fP] ] 
[ \fB\-V\fP ] [ \fB\-:\fP[\fBi\fP|\fBo\fP] ] [ \fB\-b\fP[\fBi\fP|\fBo\fP][\fBs\fP|\fBS\fP|\fBd\fP|\fBD\fP[\fIncol\fP]|\fBc\fP[\fIvar1\fP\fB/\fP\fI...\fP]] ] [ \fB\-f\fP[\fBi\fP|\fBo\fP]\fIcolinfo\fP ] [ \fB\-g\fP[\fBa\fP]\fBx\fP|\fBy\fP|\fBd\fP|\fBX\fP|\fBY\fP|\fBD\fP|[\fIcol\fP]\fBz\fP[+|-]\fIgap\fP[\fBu\fP] ] [ \fB\-m\fP[\fBi\fP|\fBo\fP][\fIflag\fP] ]
.SH DESCRIPTION
\fBmapproject\fP reads (longitude, latitude) positions from \fIinfiles\fP [or standard input] and
computes (x,y) coordinates using the specified map projection and scales.
Optionally, it can read (x,y) positions and compute (longitude, latitude) values
doing the inverse transformation.  This can be used to transform linear (x,y) points
obtained by digitizing a map of known projection to geographical coordinates.  May also
calculate distances along track, to a fixed point, or closest approach to a line.
Finally, can be used to perform various datum conversions.
Additional data fields are permitted after the first 2 columns which must have (longitude,latitude) or (x,y).
See option \fB\-:\fP on how to read (latitude,longitude) files.
.TP
\fIinfiles\fP
Data file(s) to be transformed.  If not given, standard input is read.
.TP
\fB\-J\fP
Selects the map projection. The following character determines the projection. If the
character is upper case then the argument(s) supplied as scale(s) is interpreted to be
the map width (or axis lengths), else the scale argument(s) is the map scale (see its
definition for each projection). UNIT is cm, inch, or m, depending on the \fBMEASURE_UNIT\fP
setting in \.gmtdefaults4, but this can be overridden on the command line by appending
\fBc\fP, \fBi\fP, or \fBm\fP to the \fIscale\fP or \fIwidth\fP values.  Append \fBh\fP, \fB+\fP, or \fB-\fP
to the given \fIwidth\fP if you instead want to set map height, the maximum dimension, or
the minimum dimension, respectively [Default is \fBw\fP for width].
.br
In case the central meridian is an optional parameter and it is being omitted, then the
center of the longitude range given by the \fB\-R\fP option is used. The default standard parallel
is the equator.
.br
The ellipsoid used in the map projections is user-definable by editing the \.gmtdefaults4 file
in your home directory. 73 commonly used ellipsoids and spheroids are currently
supported, and users may also specify their own custum ellipsoid parameters [Default is WGS-84].
Several GMT parameters can affect the projection: \fBELLIPSOID\fP, \fBINTERPOLANT\fP,
\fBMAP_SCALE_FACTOR\fP, and \fBMEASURE_UNIT\fP; see the \fBgmtdefaults\fP man page for details.
.br
Choose one of the following projections (The \fBE\fP or \fBC\fP after projection names
stands for Equal-Area and Conformal, respectively):
.RS
.PP
\fBCYLINDRICAL PROJECTIONS:\fP
.TP
\fB\-Jc\fP\fIlon0/lat0/scale\fP or \fB\-JC\fP\fIlon0/lat0/width\fP (Cassini).
Give projection center \fIlon0/lat0\fP and \fIscale\fP (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jcyl_stere\fP/[\fIlon0/\fP[\fIlat0/\fP]]\fIscale\fP or \fB\-JCyl_stere\fP/[\fIlon0/\fP[\fIlat0/\fP]]\fIwidth\fP (Cylindrical Stereographic).
Give central meridian \fIlon0\fP (optional), standard parallel \fIlat0\fP (optional), and \fIscale\fP along parallel (\fB1:\fP\fIxxxx\fP or UNIT/degree).
The standard parallel is typically one of these (but can be any value):
.RS
.RS
66.159467 - Miller's modified Gall
.br
55 - Kamenetskiy's First
.br
45 - Gall's Stereographic
.br
30 - Bolshoi Sovietskii Atlas Mira or Kamenetskiy's Second
.br
0 - Braun's Cylindrical
.RE
.RE
.TP
\fB\-Jj\fP[\fIlon0/\fP]\fIscale\fP or \fB\-JJ\fP[\fIlon0/\fP]\fIwidth\fP (Miller Cylindrical Projection).
Give the central meridian \fIlon0\fP (optional) and \fIscale\fP (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jm\fP[\fIlon0/\fP[\fIlat0/\fP]]\fIscale\fP or \fB\-JM\fP[\fIlon0/\fP[\fIlat0/\fP]]\fIwidth\fP
Give central meridian \fIlon0\fP (optional), standard parallel \fIlat0\fP (optional), and \fIscale\fP along parallel (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jo\fP\fIparameters\fP (Oblique Mercator \fB[C]\fP).
Specify one of:
.RS
.TP
\fB\-Jo\fP[\fBa\fP]\fIlon0/lat0/azimuth/scale\fP or \fB\-JO\fP[\fBa\fP]\fIlon0/lat0/azimuth/width\fP
Set projection center \fIlon0/lat0\fP, \fIazimuth\fP of oblique equator, and \fIscale\fP.
.TP
\fB\-Jo\fP[\fBb\fP]\fIlon0/lat0/lon1/lat1/scale\fP or \fB\-JO\fP[\fBb\fP]\fIlon0/lat0/lon1/lat1/scale\fP
Set projection center \fIlon0/lat0\fP, another point on the oblique equator \fIlon1/lat1\fP, and \fIscale\fP.
.TP
\fB\-Joc\fP\fIlon0/lat0/lonp/latp/scale\fP or \fB\-JOc\fP\fIlon0/lat0/lonp/latp/scale\fP
Set projection center \fIlon0/lat0\fP, pole of oblique projection \fIlonp/latp\fP, and \fIscale\fP.
.PP
Give \fIscale\fP along oblique equator (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.RE
.TP
\fB\-Jq\fP[\fIlon0/\fP[\fIlat0/\fP]]\fIscale\fP or \fB\-JQ\fP[\fIlon0/\fP[\fIlat0/\fP]]\fIwidth\fP (Cylindrical Equidistant).
Give the central meridian \fIlon0\fP (optional), standard parallel \fIlat0\fP (optional), and \fIscale\fP (\fB1:\fP\fIxxxx\fP or UNIT/degree).
The standard parallel is typically one of these (but can be any value):
.RS
.RS
61.7 - Grafarend and Niermann, minimum linear distortion
.br
50.5 - Ronald Miller Equirectangular
.br
43.5 - Ronald Miller, minimum continental distortion
.br
42 - Grafarend and Niermann
.br
37.5 - Ronald Miller, minimum overall distortion
.br
0 - Plate Carree, Simple Cylindrical, Plain/Plane Chart
.br
.RE
.RE
.TP
\fB\-Jt\fP\fIlon0/\fP[\fIlat0/\fP]\fIscale\fP or \fB\-JT\fP\fIlon0/\fP[\fIlat0/\fP]\fIwidth\fP
Give the central meridian \fIlon0\fP, central parallel \fIlat0\fP (optional), and \fIscale\fP (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Ju\fP\fIzone/scale\fP or \fB\-JU\fP\fIzone/width\fP (UTM - Universal Transverse Mercator \fB[C]\fP).
Give the UTM zone (A,B,1-60[C-X],Y,Z)) and \fIscale\fP (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.br
Zones: If C-X not given, prepend - or + to enforce southern or northern hemisphere conventions [northern if south > 0].
.TP
\fB\-Jy\fP[\fIlon0/\fP[\fIlat0/\fP]]\fIscale\fP or \fB\-JY\fP[\fIlon0/\fP[\fIlat0/\fP]]\fIwidth\fP (Cylindrical Equal-Area \fB[E]\fP).
Give the central meridian \fIlon0\fP (optional), standard parallel \fIlat0\fP (optional), and \fIscale\fP (\fB1:\fP\fIxxxx\fP or UNIT/degree).
The standard parallel is typically one of these (but can be any value):
.RS
.RS
50 - Balthasart
.br
45 - Gall-Peters
.br
37.0666 - Caster
.br
37.4 - Trystan Edwards
.br
37.5 - Hobo-Dyer
.br
30 - Behrman
.br
0 - Lambert (default)
.RE
.RE
.PP
\fBCONIC PROJECTIONS:\fP
.TP
\fB\-Jb\fP\fIlon0/lat0/lat1/lat2/scale\fP or \fB\-JB\fP\fIlon0/lat0/lat1/lat2/width\fP (Albers \fB[E]\fP).
Give projection center \fIlon0/lat0\fP, two standard parallels \fIlat1/lat2\fP, and \fIscale\fP (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jd\fP\fIlon0/lat0/lat1/lat2/scale\fP or \fB\-JD\fP\fIlon0/lat0/lat1/lat2/width\fP (Conic Equidistant)
Give projection center \fIlon0/lat0\fP, two standard parallels \fIlat1/lat2\fP, and \fIscale\fP (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jl\fP\fIlon0/lat0/lat1/lat2/scale\fP or \fB\-JL\fP\fIlon0/lat0/lat1/lat2/width\fP (Lambert \fB[C]\fP)
Give origin \fIlon0/lat0\fP, two standard parallels \fIlat1/lat2\fP, and \fIscale\fP along these (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jpoly\fP/[\fIlon0/\fP[\fIlat0/\fP]]\fIscale\fP or \fB\-JPoly\fP/[\fIlon0/\fP[\fIlat0/\fP]]\fIwidth\fP ((American) Polyconic).
Give the central meridian \fIlon0\fP (optional), reference parallel \fIlat0\fP (optional, default = equator),
and \fIscale\fP along central meridian (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.PP
\fBAZIMUTHAL PROJECTIONS:\fP
.sp
Except for polar aspects, \fB\-R\fPw/e/s/n will be reset to \fB\-Rg\fP.  Use \fB\-R\fP<...>\fBr\fP for smaller regions.
.TP
\fB\-Ja\fP\fIlon0/lat0\fP[\fI/horizon\fP]\fI/scale\fP or \fB\-JA\fP\fIlon0/lat0\fP[\fI/horizon\fP]\fI/width\fP (Lambert \fB[E]\fP).
\fIlon0/lat0\fP specifies the projection center.
\fIhorizon\fP specifies the max distance from projection center (in degrees, <= 180, default 90).
Give \fIscale\fP as \fB1:\fP\fIxxxx\fP or \fIradius/lat\fP, where \fIradius\fP is distance
in UNIT from origin to the oblique latitude \fIlat\fP.
.TP
\fB\-Je\fP\fIlon0/lat0\fP[\fI/horizon\fP]\fI/scale\fP or \fB\-JE\fP\fIlon0/lat0\fP[\fI/horizon\fP]\fI/width\fP (Azimuthal Equidistant).
\fIlon0/lat0\fP specifies the projection center.
\fIhorizon\fP specifies the max distance from projection center (in degrees, <= 180, default 180).
Give \fIscale\fP as \fB1:\fP\fIxxxx\fP or \fIradius/lat\fP, where \fIradius\fP is distance
in UNIT from origin to the oblique latitude \fIlat\fP.
.TP
\fB\-Jf\fP\fIlon0/lat0\fP[\fI/horizon\fP]\fI/scale\fP or \fB\-JF\fP\fIlon0/lat0\fP[\fI/horizon\fP]\fI/width\fP (Gnomonic).
\fIlon0/lat0\fP specifies the projection center.
\fIhorizon\fP specifies the max distance from projection center (in degrees, < 90, default 60).
Give \fIscale\fP as \fB1:\fP\fIxxxx\fP or \fIradius/lat\fP, where \fIradius\fP is distance
in UNIT from origin to the oblique latitude \fIlat\fP.
.TP
\fB\-Jg\fP\fIlon0/lat0\fP[\fI/horizon\fP]\fI/scale\fP or \fB\-JG\fP\fIlon0/lat0\fP[\fI/horizon\fP]\fI/width\fP (Orthographic).
\fIlon0/lat0\fP specifies the projection center.
\fIhorizon\fP specifies the max distance from projection center (in degrees, <= 90, default 90).
Give \fIscale\fP as \fB1:\fP\fIxxxx\fP or \fIradius/lat\fP, where \fIradius\fP is distance
in UNIT from origin to the oblique latitude \fIlat\fP.
.TP
\fB\-Jg\fP\fIlon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale\fP or \fB\-JG\fP\fIlon0/lat0/altitude/azimuth/tilt/twist/Width/Height/width\fP (General Perspective).
\fIlon0/lat0\fP specifies the projection center.
\fIaltitude\fP is the height (in km) of the viewpoint above local sea level.
If \fIaltitude\fP is less than 10, then it is the distance from the center of the earth
to the viewpoint in earth radii. If \fIaltitude\fP has a suffix \fBr\fP then it is the radius
from the center of the earth in kilometers.
\fIazimuth\fP is measured to the east of north of view.
\fItilt\fP is the upward tilt of the plane of projection. If \fItilt\fP is negative, then the
viewpoint is centered on the horizon.
Further, specify the clockwise \fItwist\fP, \fIWidth\fP, and
\fIHeight\fP of the viewpoint in degrees.
Give \fIscale\fP as \fB1:\fP\fIxxxx\fP or \fIradius/lat\fP, where \fIradius\fP is distance
in UNIT from origin to the oblique latitude \fIlat\fP.
.TP
\fB\-Js\fP\fIlon0/lat0\fP[\fI/horizon\fP]\fI/scale\fP or \fB\-JS\fP\fIlon0/lat0\fP[\fI/horizon\fP]\fI/width\fP (General Stereographic \fB[C]\fP).
\fIlon0/lat0\fP specifies the projection center.
\fIhorizon\fP specifies the max distance from projection center (in degrees, < 180, default 90).
Give \fIscale\fP as \fB1:\fP\fIxxxx\fP (true at pole) or \fIlat0\fP/\fB1:\fP\fIxxxx\fP (true at standard parallel \fIlat0\fP)
or \fIradius/lat\fP (\fIradius\fP in UNIT from origin to the oblique latitude \fIlat\fP).
Note if \fB1:\fP\fIxxxx\fP is used then to specify \fIhorizon\fP you must also specify the \fIlat0\fP as +-90 to avoid ambiguity.
.PP
\fBMISCELLANEOUS PROJECTIONS:\fP
.TP
\fB\-Jh\fP[\fIlon0/\fP]\fIscale\fP or \fB\-JH\fP[\fIlon0/\fP]\fIwidth\fP (Hammer \fB[E]\fP).
Give the central meridian \fIlon0\fP (optional) and \fIscale\fP along equator (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Ji\fP[\fIlon0/\fP]\fIscale\fP or \fB\-JI\fP[\fIlon0/\fP]\fIwidth\fP (Sinusoidal \fB[E]\fP).
Give the central meridian \fIlon0\fP (optional) and \fIscale\fP along equator (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jkf\fP[\fIlon0/\fP]\fIscale\fP or \fB\-JKf\fP[\fIlon0/\fP]\fIwidth\fP (Eckert IV) \fB[E]\fP).
Give the central meridian \fIlon0\fP (optional) and \fIscale\fP along equator (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jk\fP[\fBs\fP][\fIlon0/\fP]\fIscale\fP or \fB\-JK\fP[\fBs\fP][\fIlon0/\fP]\fIwidth\fP (Eckert VI) \fB[E]\fP).
Give the central meridian \fIlon0\fP (optional) and \fIscale\fP along equator (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jn\fP[\fIlon0/\fP]\fIscale\fP or \fB\-JN\fP[\fIlon0/\fP]\fIwidth\fP (Robinson).
Give the central meridian \fIlon0\fP (optional) and \fIscale\fP along equator (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jr\fP[\fIlon0/\fP]\fIscale\fP \fB\-JR\fP[\fIlon0/\fP]\fIwidth\fP (Winkel Tripel).
Give the central meridian \fIlon0\fP (optional) and \fIscale\fP along equator (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jv\fP[\fIlon0/\fP]\fIscale\fP or \fB\-JV\fP[\fIlon0/\fP]\fIwidth\fP (Van der Grinten).
Give the central meridian \fIlon0\fP (optional) and \fIscale\fP along equator (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.TP
\fB\-Jw\fP[\fIlon0/\fP]\fIscale\fP or \fB\-JW\fP[\fIlon0/\fP]\fIwidth\fP (Mollweide \fB[E]\fP).
Give the central meridian \fIlon0\fP (optional) and \fIscale\fP along equator (\fB1:\fP\fIxxxx\fP or UNIT/degree).
.PP
\fBNON-GEOGRAPHICAL PROJECTIONS:\fP
.TP
\fB\-Jp\fP[\fBa\fP]\fIscale\fP[\fI/origin\fP][\fBr\fP|\fBz\fP] or \fB\-JP\fP[\fBa\fP]\fIwidth\fP[\fI/origin\fP][\fBr\fP|\fBz\fP] (Polar coordinates (theta,r))
Optionally insert \fBa\fP after \fB\-Jp\fP [ or \fB\-JP\fP] for
azimuths CW from North instead of directions CCW from East [Default].
Optionally append /\fIorigin\fP in degrees to indicate an angular offset [0]).
Finally, append \fBr\fP if r is elevations in degrees (requires s >= 0 and n <= 90)
or \fBz\fP if you want to annotate depth rather than radius [Default].
Give \fIscale\fP in UNIT/r-unit.
.TP
\fB\-Jx\fP\fIx-scale\fP[\fI/y-scale\fP] or \fB\-JX\fP\fIwidth\fP[\fI/height\fP] (Linear, log, and power scaling)
Give \fIx-scale\fP (\fB1:\fP\fIxxxx\fP or UNIT/x-unit) and/or \fIy-scale\fP (\fB1:\fP\fIxxxx\fP or UNIT/y-unit); or
specify \fIwidth\fP and/or \fIheight\fP in UNIT.
\fIy-scale\fP=\fIx-scale\fP if not specified separately and using \fB1:\fP\fIxxxx\fP implies that x-unit and y-unit are in
meters.
Use negative scale(s) to reverse the direction of an axis (e.g., to have y be positive down). Set
\fIheight\fP or \fIwidth\fP to 0 to have it recomputed based on the implied scale of the other axis.
Optionally, append to \fIx-scale\fP, \fIy-scale\fP, \fIwidth\fP or \fIheight\fP one of the following:
.RS
.TP
.B d
Data are geographical coordinates (in degrees).
.TP
.B l
Take log10 of values before scaling.
.TP
\fBp\fP\fIpower\fP
Raise values to \fIpower\fP before scaling.
.TP
.B t
Input coordinates are time relative to \fBTIME_EPOCH\fP.
.TP
.B T
Input coordinates are absolute time.
.PP
Default axis lengths (see \fBgmtdefaults\fP) can be invoked
using \fB\-JXh\fP (for landscape); \fB\-JXv\fP (for portrait) will swap the x- and y-axis lengths.
The default unit for this installation is either cm or inch, as defined in the file
share/gmt.conf. However, you may change this by editing your \.gmtdefaults4 file(s).
.RE
.RE
.TP
\fB\-R\fP
\fIxmin\fP, \fIxmax\fP, \fIymin\fP, and \fIymax\fP specify the Region of interest.  For geographic
regions, these limits correspond to \fIwest, east, south,\fP and \fInorth\fP and you may specify them
in decimal degrees or in [+-]dd:mm[:ss.xxx][W|E|S|N] format.  Append \fBr\fP if lower left and upper right
map coordinates are given instead of w/e/s/n.  The two shorthands \fB\-Rg\fP and \fB\-Rd\fP stand for global domain
(0/360 and -180/+180 in longitude respectively, with -90/+90 in latitude).  Alternatively, specify the name
of an existing grid file and the \fB\-R\fP settings (and grid spacing, if applicable) are copied from the grid.
For calendar time coordinates you may either give (a) relative
time (relative to the selected \fBTIME_EPOCH\fP and in the selected \fBTIME_UNIT\fP; append \fBt\fP to
\fB\-JX\fP|\fBx\fP), or (b) absolute time of the form [\fIdate\fP]\fBT\fP[\fIclock\fP]
(append \fBT\fP to \fB\-JX\fP|\fBx\fP).  At least one of \fIdate\fP and \fIclock\fP
must be present; the \fBT\fP is always required.  The \fIdate\fP string must be of the form [-]yyyy[-mm[-dd]]
(Gregorian calendar) or yyyy[-Www[-d]] (ISO week calendar), while the \fIclock\fP string must be of
the form hh:mm:ss[.xxx].  The use of delimiters and their type and positions must be exactly as indicated
(however, input, output and plot formats are customizable; see \fBgmtdefaults\fP). 
Special case for the UTM projection: If \fB\-C\fP is used and \fB\-R\fP is not given then the region is set to coincide with
the given UTM zone so as to preserve the full ellipsoidal solution (See RESTRICTIONS for more information).
.SH OPTIONS
No space between the option flag and the associated arguments.
.TP
\fIinfile(s)\fP
input file(s) with 2 or more columns. If no file(s) is given, \fBmapproject\fP will read the standard input.
.TP
\fB\-A\fP[\fBf\fP|\fBb\fP]
\fB\-A\fP calculates the (forward) azimuth from fixed point \fIlon/lat\fP to each data point.  Use \fB\-Ab\fP to get
back-azimuth from data points to fixed point.  Upper case \fBF\fP or \fBB\fP will convert from geodetic to
geocentric latitudes and estimate azimuth of geodesics (assuming the current ellipsoid is not a sphere).
If no fixed point is given then we compute the azimuth (or back-azimuth) from the previous point.
.TP
\fB\-C\fP
Set center of projected coordinates to be at map projection center [Default is lower left corner].
Optionally, add offsets in the projected units to be added (or subtracted when \fB\-I\fP is set) to (from)
the projected coordinates, such as false eastings and northings for particular projection zones [0/0].
The unit used for the offsets is the plot distance unit in effect (see \fBMEASURE_UNIT\fP) unless \fB\-F\fP is used,
in which case the offsets are always in meters.
.TP
\fB\-D\fP
Temporarily override \fBMEASURE_UNIT\fP and use \fBc\fP (cm), \fBi\fP (inch),
\fBm\fP (meter), or \fBp\fP (points) instead.  Cannot be used with \fB\-F\fP.
.TP
\fB\-E\fP
Convert from geodetic (lon, lat, height) to Earth Centered Earth Fixed (ECEF) (x,y,z) coordinates (add \fB\-I\fP for the
inverse conversion).  Append
datum ID (see \fB\-Qd\fP) or give \fIellipsoid\fP:\fIdx,dy,dz\fP
where \fIellipsoid\fP may be an ellipsoid ID (see \fB\-Qe\fP) or given as \fIa\fP[,\fIinv_f\fP], where \fIa\fP is the
semi-major axis and \fIinv_f\fP is the inverse flattening (0 if omitted).
If \fIdatum\fP is - or not given we assume WGS-84.
.TP
\fB\-F\fP
Force 1:1 scaling, i.e., output (or input, see \fB\-I\fP) data are in actual projected meters.  To specify other units,
append \fBk\fP (km), \fBm\fP (mile), \fBn\fP (nautical mile), \fBi\fP (inch), \fBc\fP (cm), or \fBp\fP (points).
Without \fB\-F\fP, the output (or input, see \fB\-I\fP) are in the units specified by \fBMEASURE_UNIT\fP (but see \fB\-D\fP).
.TP
\fB\-G\fP
Calculate distances along track OR to the optional point set with \fB\-G\fP\fIx0/y0\fP.  Append \IT(unit), the distance unit;
choose among \fBe\fP (m), \fBk\fP (km), \fBm\fP (mile), \fBn\fP (nautical mile), \fBd\fP (spherical degree),
\fBc\fP (Cartesian distance using input coordinates) or \fBC\fP (Cartesian distance using projected coordinates).  The
last unit requires \fB\-R\fP and \fB\-J\fP to be set.  Upper case  \fBE\fP, \fBK\fP, \fBM\fP, \fBN\fP, or \fBD\fP
will use exact methods for geodesic distances (Rudoe's method for distances in length units and employing geocentric\"'
latitudes in degree calculations, assuming the current ellipsoid is not spherical).  With no fixed point we
calculate cumulate distances along track. To obtain incremental distance between successive points, use \fB\-G-\fP.
To specify the 2nd point via two extra columns in the input file, choose \fB\-G+\fP.
.TP
\fB\-H\fP
Input file(s) has header record(s).  If used, the default number of header records is \fBN_HEADER_RECS\fP.
Use \fB\-Hi\fP if only input data should have header records [Default will write out header records if the
input data have them]. Blank lines and lines starting with # are always skipped.
.TP
\fB\-I\fP
Do the Inverse transformation, i.e. get (longitude,latitude) from (x,y) data.
.TP
\fB\-L\fP
Determine the shortest distance from the input data points to the line(s) given in the ASCII multi-segment file \fIline.xy\fP.
The distance and the coordinates of the nearest point will be appended to the output as three new columns.
Append the distance unit; choose among \fBe\fP (m), \fBk\fP (km), \fBm\fP (mile), \fBn\fP (nautical mile), \fBd\fP (spherical degree),
\fBc\fP (Cartesian distance using input coordinates) or \fBC\fP (Cartesian distance using projected coordinates).  The
last unit requires \fB\-R\fP and \fB\-J\fP to be set.  A spherical approximation is used for geographic data.
Finally, append \fB+\fP to report the line segment id and the fractional point number instead of lon/lat of the nearest point.
.TP
\fB\-Q\fP
List all projection parameters.  To only list datums, use \fB\-Qd\fP.  To only list ellipsoids, use \fB\-Qe\fP.
.TP
\fB\-S\fP
Suppress points that fall outside the region.
.TP
\fB\-T\fP
Coordinate conversions between datums \fIfrom\fP and \fIto\fP using the standard Molodensky transformation.  Use \fB\-Th\fP if 3rd input column has
height above ellipsoid [Default assumes height = 0, i.e., on the ellipsoid].  Specify datums using the
datum ID (see \fB\-Qd\fP) or give \fIellipsoid\fP:\fIdx,dy,dz\fP
where \fIellipsoid\fP may be an ellipsoid ID (see \fB\-Qe\fP) or given as \fIa\fP[,\fIinv_f\fP], where \fIa\fP is the
semi-major axis and \fIinv_f\fP is the inverse flattening (0 if omitted).
If \fIdatum\fP is - or not given we assume WGS-84.
\fB\-T\fP may be used in conjunction with \fB\-R\fP \fB\-J\fP to change the datum before coordinate projection
(add \fB\-I\fP to apply the datum conversion after the inverse projection).  Make sure that the
\fBELLIPSOID\fP setting is correct for your case.
.TP
\fB\-V\fP
Selects verbose mode, which will send progress reports to stderr [Default runs "silently"].
.TP
\fB\-:\fP
Toggles between (longitude,latitude) and (latitude,longitude) input and/or output.  [Default is (longitude,latitude)].
Append \fBi\fP to select input only or \fBo\fP to select output only.  [Default affects both].
.TP
\fB\-bi\fP
Selects binary input.
Append \fBs\fP for single precision [Default is \fBd\fP (double)].
Uppercase \fBS\fP or \fBD\fP will force byte-swapping.
Optionally, append \fIncol\fP, the number of columns in your binary input file
if it exceeds the columns needed by the program.
Or append \fBc\fP if the input file is netCDF. Optionally, append \fIvar1\fP\fB/\fP\fIvar2\fP\fB/\fP\fI...\fP to
specify the variables to be read.
[Default is 2 input columns].
.TP
\fB\-bo\fP
Selects binary output.
Append \fBs\fP for single precision [Default is \fBd\fP (double)].
Uppercase \fBS\fP or \fBD\fP will force byte-swapping.
Optionally, append \fIncol\fP, the number of desired columns in your binary output file.
[Default is same as input].
.TP
\fB\-f\fP
Special formatting of input and/or output columns (time or geographical data).
Specify \fBi\fP or \fBo\fP to make this apply only to input or output [Default applies to both].
Give one or more columns (or column ranges) separated by commas.
Append \fBT\fP (absolute calendar time), \fBt\fP (relative time in chosen \fBTIME_UNIT\fP since \fBTIME_EPOCH\fP),
\fBx\fP (longitude), \fBy\fP (latitude), or \fBf\fP (floating point) to each column
or column range item.  Shorthand \fB\-f\fP[\fBi\fP|\fBo\fP]\fBg\fP means \fB\-f\fP[\fBi\fP|\fBo\fP]0\fBx\fP,1\fBy\fP
(geographic coordinates).
.TP
\fB\-g\fP
Examine the spacing between consecutive data points in order to impose breaks in the line.
Append \fBx\fP|\fBX\fP or \fBy\fP|\fBY\fP to define a gap when there is a large enough change in the x or y coordinates, respectively,
or \fBd\fP|\fBD\fP for distance gaps; use upper case to calculate gaps from projected coordinates.  For gap-testing on other columns
use [\fIcol\fP]\fBz\fP; if \fIcol\fP is not prepended the it defaults to 2 (i.e., 3rd column).
Append [+|-]\fIgap\fP and optionally a unit \fBu\fP.  Regarding optional signs: -ve means previous minus current column value must exceed
|\fIgap\fP to be a gap, +ve means current minus previous column value must exceed \fIgap\fP, and no sign means the absolute value of the
difference must exceed \fIgap\fP.
For geographic data (\fBx\fP|\fBy\fP|\fBd\fP), the unit \fBu\fP may be m\fBe\fPter [Default], \fBk\fPilometer, \fBm\fPiles, or \fBn\fPautical miles.
For projected data (\fBX\fP|\fBY\fP|\fBD\fP), choose from \fBi\fPnch, \fBc\fPentimeter, \fBm\fPeter, or \fBp\fPoints [Default unit set by MEASURE_UNIT].
Note: For \fBx\fP|\fBy\fP|\fBz\fP with time data the unit is instead controlled by TIME_UNIT.
Repeat the option to specify multiple criteria, of which any can be met to produce a line break.
Issue an additional \fB\-ga\fP to indicate that all criteria must be met instead.
.TP
\fB\-m\fP
Multiple segment file(s).  Segments are separated by a special record.
For ASCII files the first character must be \fIflag\fP [Default is '>'].
For binary files all fields must be NaN and \fB\-b\fP must
set the number of output columns explicitly.  By default the \fB\-m\fP
setting applies to both input and output.  Use \fB\-mi\fP and \fB\-mo\fP
to give separate settings to input and output.
.SH ASCII FORMAT PRECISION
The ASCII output formats of numerical data are controlled by parameters in
your \.gmtdefaults4 file.  Longitude and latitude are formatted according to
\fBOUTPUT_DEGREE_FORMAT\fP, whereas other values are formatted according
to \fBD_FORMAT\fP.  Be aware that the format in effect can lead to loss of
precision in the output, which can lead to various problems downstream.  If
you find the output is not written with enough precision, consider switching
to binary output (\fB\-bo\fP if available) or specify more decimals using
the \fBD_FORMAT\fP setting.
.SH EXAMPLES
To transform a file with (longitude,latitude) into (x,y) positions in cm on
a Mercator grid for a given scale of 0.5 cm per degree, run
.br
.sp
\fBmapproject\fP lonlatfile \fB\-R\fP20/50/12/25 \fB\-Jm\fP0.5\fBc\fP > xyfile
.br
.sp
To transform several 2-column, binary, double precision files with (latitude,longitude) into (x,y) positions in inch on
a Transverse Mercator grid (central longitude 75W) for scale = 1:500000 and suppress those points
that would fall outside the map area, run
.br
.sp
\fBmapproject\fP tracks.* \fB\-R\fP-80/-70/20/40 \fB\-Jt\fP-75/1:500000 \fB\-:\fP \fB\-S\fP \fB\-Di\fP \fB\-bo\fP \fB\-bi\fP2 > tmfile.b
.br
.sp
To convert the geodetic coordinates (lon, lat, height) in the file old.dat from the NAD27 CONUS datum
(Datum ID 131 which uses the Clarke-1866 ellipsoid) to WGS 84, run
.br
.sp
\fBmapproject\fP old.dat \fB\-Th\fP131 > new.dat
.br
.sp
To compute the closest distance (in km) between each point in the input file quakes.dat and the
line segments given in the multi-segment ASCII file coastline.xy, run
.br
.sp
\fBmapproject\fP quakes.dat \fB\-L\fPcoastline.xy/k > quake_dist.dat
.SH RESTRICTIONS
The rectangular input region set with \fB\-R\fP will in general be mapped into a
non-rectangular grid.  Unless \fB\-C\fP is set, the leftmost point on this grid has xvalue = 0.0, and the
lowermost point will have yvalue = 0.0. Thus, before you digitize a map, run the
extreme map coordinates through \fBmapproject\fP using the appropriate scale and see
what  (x,y) values they are mapped onto.  Use these values when setting up for
digitizing in order to have the inverse transformation work correctly, or alternatively,
use \fBawk\fP to scale and shift the (x,y) values before transforming.
.br
For some projection, a spherical solution may be used despite the user having
selected an ellipsoid.  This occurs when the users \fB\-R\fP setting implies a
region that exceeds the domain in which the ellipsoidal series expansions are
valid.  These are the conditions: (1) Lambert Conformal Conic (\fB\-JL\fP)and Albers
Equal-Area (\fB\-JB\fP) will use the spherical solution when the map scale exceeds
1.0E7.  (2) Transverse Mercator (\fB\-JT\fP) and UTM (\fB\-JU\fP) will will use the
spherical solution when either the west or east boundary given in \fB\-R\fP is
more than 10 degrees from the central meridian, and (3) same for Cassini (\fB\-JC\fP)
but with a limit of only 4 degrees.
.SH ELLIPSOIDS AND SPHEROIDS
\fBGMT\fP will use ellipsoidal formulae if they are implemented and the user have
selected an ellipsoid as the reference shape (see \fBELLIPSOID\fP in \fBgmtdefaults\fP).  The user
needs to be aware of a few potential pitfalls: (1)  For some projections,
such as Transverse Mercator, Albers, and Lamberts conformal conic we use the
ellipsoidal expressions when the areas mapped are small, and switch to the
spherical expressions (and substituting the appropriate auxiliary latitudes)
for larger maps.  The ellipsoidal formulae are used as follows: (a) Transverse
Mercator: When all points are within 10 degrees of central meridian, (b) Conic
projections when longitudinal range is less than 90 degrees, (c) Cassini
projection when all points are within 4 degrees of central meridian. (2) When
you are trying to match some historical data (e.g., coordinates obtained with
a certain projection and a certain reference ellipsoid) you may find that \fBGMT\fP
gives results that are slightly different.  One likely source of this mismatch
is that older calculations often used less significant digits.  For instance,
Snyder's examples often use the Clarke 1866 ellipsoid (defined by him as\"'
having a flattening f = 1/294.98).  From f we get the eccentricity squared to
be 0.00676862818 (this is what \fBGMT\fP uses), while Snyder rounds off and uses
0.00676866.  This difference can give discrepancies of several tens of cm.
If you need to reproduce coordinates projected with this slightly different
eccentricity, you should specify your own ellipsoid with the same parameters
as Clarke 1866, but with f = 1/294.97861076.  Also, be aware that older data
may be referenced to different datums, and unless you know which datum was
used and convert all data to a common datum you may experience mismatches of
tens to hundreds of meters. (3) Finally, be aware that \fBMAP_SCALE_FACTOR\fP
have certain default values for some projections so you may have to override
the setting in order to match results produced with other settings.
.SH "SEE ALSO"
.IR gmtdefaults (1),
.IR GMT (1),
.IR project (1)
.SH REFERENCES
Bomford, G., 1952, Geodesy, Oxford U. Press.
.br
Snyder, J. P., 1987, Map Projections \- A Working Manual, U.S. Geological Survey Prof. Paper 1395.
.br
Vanicek, P. and Krakiwsky, E, 1982, Geodesy \- The Concepts, North-Holland Publ., ISBN: 0 444 86149 1.
.br