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<HTML>
<HEAD>
<TITLE>mapproject</TITLE>
</HEAD>
<BODY>
<H1>mapproject</H1>
<HR>
<PRE>
<!-- Manpage converted by man2html 3.0.1 -->
mapproject - Forward and Inverse map transformation of 2-D
coordinates
</PRE>
<H2>SYNOPSIS</H2><PRE>
<B>mapproject</B> <I>infiles</I> <B>-J</B><I>parameters</I> <B>-R</B><I>west/east/south/north</I>[<B>r</B>]
[ <B>-C</B> ] [ <B>-Dc|i|m|p</B> ] [ <B>-F</B>[<B>k|m|n|i|c|p</B>] ] [ <B>-H</B>[<I>nrec</I>] ] [ <B>-I</B>
] [ <B>-M</B>[<I>flag</I>] ] [ <B>-S</B> ] [ <B>-V</B> ] [ <B>-:</B> ] [ <B>-bi</B>[<B>s</B>][<I>n</I>] ] [ <B>-bo</B>[<B>s</B>]
]
</PRE>
<H2>DESCRIPTION</H2><PRE>
<B>mapproject</B> reads (longitude, latitude) positions from
<I>infiles</I> [or standard input] and computes (x,y) coordinates
using the specified map projection and scales. Option
ally, 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 coor
dinates. Additional data fields are permitted after the
first 2 columns which must have (longitude,latitude) or
(x,y). See option <B>-:</B> on how to read (latitude,longitude)
files.
No space between the option flag and the associ
ated arguments. Use upper case for the option flags and
lower case for modifiers.
<I>infiles</I>
Data file(s) to be transformed. If not given, stan
dard input is read.
<B>-J</B> 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 MEA
SURE_UNIT setting in .<A HREF="gmtdefaults.html">gmtdefaults</A>, but this can be
overridden on the command line by appending c, i,
or m to the scale/width values. Choose one of the
following projections (The <B>E</B> or <B>C</B> after projection
names stands for Equal-Area and Conformal, respec
tively):
<B>CYLINDRICAL</B> <B>PROJECTIONS:</B>
<B>-Jc</B><I>lon0/lat0/scale</I> or <B>-JC</B><I>lon0/lat0/width</I> (Cassini)
Give projection center and scale (1:xxxx or
UNIT/degree).
<B>-Jj</B><I>lon0/scale</I> or <B>-JJ</B><I>lon0/width</I> (Miller Cylindrical
Projection)
Give the central meridian and scale (1:xxxx
or UNIT/degree).
Give scale along equator (1:xxxx or
UNIT/degree).
<B>-Jm</B><I>lon0/lat0/scale</I> or <B>-JM</B><I>lon0/lat0/width</I>
Give central meridian, standard
latitude and scale along parallel (1:xxxx or
UNIT/degree).
<B>-Jo</B><I>parameters</I> (Oblique Mercator <B>[C]</B>). Specify one
of:
<B>-Joa</B><I>lon0/lat0/azimuth/scale</I> or
<B>-JOa</B><I>lon0/lat0/azimuth/width</I>
Set projection center, azimuth of
oblique equator, and scale.
<B>-Job</B><I>lon0/lat0/lon1/lat1/scale</I> or
<B>-JOb</B><I>lon0/lat0/lon1/lat1/scale</I>
Set projection center, another
point on the oblique equator, and scale.
<B>-Joc</B><I>lon0/lat0/lonp/latp/scale</I> or
<B>-JOc</B><I>lon0/lat0/lonp/latp/scale</I>
Set projection center, pole of
oblique projection, and scale.
Give scale along oblique equator (1:xxxx or
UNIT/degree).
<B>-Jq</B><I>lon0/scale</I> or <B>-JQ</B><I>lon0/width</I> (Equidistant Cylin
drical Projection (Plate Carree))
Give the central meridian and scale (1:xxxx
or UNIT/degree).
<B>-Jt</B><I>parameters</I> (Transverse Mercator <B>[C]</B>). Specify
one of:
<B>-Jt</B><I>lon0/scale</I> or <B>-JT</B><I>lon0/width</I>
Give the central meridian and scale
(1:xxxx or UNIT/degree).
<B>-Jt</B><I>lon0/lat0/scale</I> or <B>-JT</B><I>lon0/lat0/width</I>
Give projection center and scale
(1:xxxx or UNIT/degree).
<B>-Ju</B><I>zone/scale</I> or <B>-JU</B><I>zone/width</I> (UTM - Universal
Transverse Mercator <B>[C]</B>)
Give the zone number (1-60) and scale
(1:xxxx or UNIT/degree).
zones: prepend - or + to enforce southern
or northern hemisphere conventions [northern if
south > 0].
<B>-Jy</B><I>lon0/lats/scale</I> or <B>-JY</B><I>lon0/lats/width</I> (Basic
Cylindrical Projections <B>[E]</B>)
Give the central meridian, standard paral
lel, and scale (1:xxxx or UNIT/degree).
The standard parallel is typically one of
these (but can be any value):
45 - The Peters projection
37.4 - The Trystan Edwards projection
30 - The Behrman projection
0 - The Lambert projection
<B>[E]</B>).
<I>lon0/lat0</I> specifies the projection center.
Give scale as 1:xxxx or <I>radius/lat</I>, where
<I>radius</I> is distance
in UNIT from origin to the oblique latitude
<I>lat</I>.
<B>-Je</B><I>lon0/lat0/scale</I> or <B>-JE</B><I>lon0/lat0/width</I> (Equidis
tant).
<I>lon0/lat0</I> specifies the projection center.
Give scale as 1:xxxx or <I>radius/lat</I>, where
<I>radius</I> is distance
in UNIT from origin to the oblique latitude
<I>lat</I>.
<B>-Jf</B><I>lon0/lat0/horizon/scale</I> or <B>-JF</B><I>lon0/lat0/hori</I>
<I>zon/width</I> (Gnomonic).
<I>lon0/lat0</I> specifies the projection center.
<I>horizon</I> specifies the max distance from
projection center (in degrees, < 90).
Give scale as 1:xxxx or <I>radius/lat</I>, where
<I>radius</I> is distance
in UNIT from origin to the oblique latitude
<I>lat</I>.
<B>-Jg</B><I>lon0/lat0/scale</I> or <B>-JG</B><I>lon0/lat0/width</I> (Ortho
graphic).
<I>lon0/lat0</I> specifies the projection center.
Give scale as 1:xxxx or <I>radius/lat</I>, where
<I>radius</I> is distance
in UNIT from origin to the oblique latitude
<I>lat</I>.
<B>-Js</B><I>lon0/lat0/scale</I> or <B>-JS</B><I>lon0/lat0/width</I> (General
Stereographic <B>[C]</B>)
<I>lon0/lat0</I> specifies the projection center.
Give scale as 1:xxxx (true at pole) or
<I>slat</I>/1:xxxx (true at standard parallel <I>slat</I>)
or <I>radius/lat</I> (<I>radius</I> in UNIT from origin
to the oblique latitude <I>lat</I>).
<B>CONIC</B> <B>PROJECTIONS:</B>
<B>-Jb</B><I>lon0/lat0/lat1/lat2/scale</I> or
<B>-JB</B><I>lon0/lat0/lat1/lat2/width</I> (Albers <B>[E]</B>)
Give projection center, two standard paral
lels, and scale (1:xxxx or UNIT/degree).
<B>-Jd</B><I>lon0/lat0/lat1/lat2/scale</I> or
<B>-JD</B><I>lon0/lat0/lat1/lat2/width</I> (Equidistant)
Give projection center, two standard paral
lels, and scale (1:xxxx or UNIT/degree).
<B>-Jl</B><I>lon0/lat0/lat1/lat2/scale</I> or
<B>-JL</B><I>lon0/lat0/lat1/lat2/width</I> (Lambert <B>[C]</B>)
Give origin, 2 standard parallels, and
scale along these (1:xxxx or UNIT/degree).
Give the central meridian and scale along
equator (1:xxxx or UNIT/degree).
<B>-Ji</B><I>lon0/scale</I> or <B>-JI</B><I>lon0/width</I> (Sinusoidal <B>[E]</B>)
Give the central meridian and scale along
equator (1:xxxx or UNIT/degree).
<B>-Jk</B>[<B>f|s</B>]<I>lon0/scale</I> or <B>-JK</B>[<B>f|s</B>]<I>lon0/width</I> (Eckert IV
(f) and VI (s) <B>[E]</B>)
Give the central meridian and scale along
equator (1:xxxx or UNIT/degree).
<B>-Jn</B><I>lon0/scale</I> or <B>-JN</B><I>lon0/width</I> (Robinson)
Give the central meridian and scale along
equator (1:xxxx or UNIT/degree).
<B>-Jr</B><I>lon0/scale</I> <B>-JR</B><I>lon0/width</I> (Winkel Tripel)
Give the central meridian and scale along
equator (1:xxxx or UNIT/degree).
<B>-Jv</B><I>lon0/scale</I> or <B>-JV</B><I>lon0/width</I> (Van der Grinten)
Give the central meridian and scale along
equator (1:xxxx or UNIT/degree).
<B>-Jw</B><I>lon0/scale</I> or <B>-JW</B><I>lon0/width</I> (Mollweide <B>[E]</B>)
Give the central meridian and scale along
equator (1:xxxx or UNIT/degree).
<B>NON-GEOGRAPHICAL</B> <B>PROJECTIONS:</B>
<B>-Jp</B>[<B>a</B>]<I>scale</I>[<I>/origin</I>] or <B>-JP</B>[<B>a</B>]<I>width</I>[<I>/origin</I>] (Lin
ear projection for polar (theta,r) coordinates,
optionally insert <B>a</B> after <B>-Jp</B> [ or <B>-JP</B>] for
azimuths CW from North instead of directions CCW
from East [default], optionally append /<I>origin</I> in
degrees to indicate an angular offset [0]).
Give scale in UNIT/r-unit.
<B>-Jx</B><I>x-scale</I>[<I>/y-scale</I>] or <B>-JX</B><I>width</I>[<I>/height</I>]
<I>scale</I> [or <I>width</I>] can be any of the following 3
types:
<B>-Jx</B><I>scale</I> - Regular linear scaling.
<B>-Jx</B><I>scale</I><B>l</B> - Take log10 of values before
scaling.
<B>-Jx</B><I>scale</I><B>p</B><I>power</I> - Raise values to <I>power</I>
before scaling.
Give <I>x-scale</I> in UNIT/x-unit and <I>y-scale</I> in UNIT/y-
unit. (<I>y-scale</I> = <I>x-scale</I> if not specified sepa
rately). Use negative scale(s) to reverse the
direction of an axis (e.g., to have y be positive
down).
Append a single <B>d</B> if data are geographical coordi
nates in degrees. Default axes lengths (see gmtde
faults) can be invoked using <B>-JXh</B> (for landscape);
<B>-JXv</B> (for portrait) will swap the x- and y-axes
lengths. The <B><A HREF="GMT.html">GMT</A></B> default unit for this installa
tion is UNIT. However, you may change this by edit
ing your .gmtdefaults file(s) (run gmtdefaults to
is user-definable by editing the .gmtdefaults file
in your home directory. 13 commonly used ellipsoids
and a spheroid are currently supported, and users
may also specify their own ellipsoid parameters
(see man gmtdefaults for more details). <B><A HREF="GMT.html">GMT</A></B>
default is WGS-84. Several GMT parameters can
affect the projection: ELLIPSOID, INTERPOLANT,
MAP_SCALE_FACTOR, and MEASURE_UNIT; see the <B>gmtde</B>
<B>faults</B> man page for details.
<B>-R</B> <I>west,</I> <I>east,</I> <I>south,</I> and <I>north</I> specify the Region of
interest. To specify boundaries in degrees and min
utes [and seconds], use the dd:mm[:ss] format.
Append <B>r</B> if lower left and upper right map coordi
nates are given instead of wesn.
</PRE>
<H2>OPTIONS</H2><PRE>
<I>infile(s)</I>
input file(s) with 2 or more columns. If no file(s)
is given, mapproject will read standard input.
<B>-C</B> Set center of projected coordinates to be at map
projection center [Default is lower left corner].
<B>-D</B> Temporarily override MEASURE_UNIT and use <B>c</B> (cm), <B>i</B>
(inch), <B>m</B> (meter), or <B>p</B> (points) instead. Cannot be
used with <B>-F</B>.
<B>-F</B> Force 1:1 scaling, i.e., output (or input, see <B>-I</B>)
data are in actual projected meters. To specify
other units, append <B>k</B> (km), <B>m</B> (mile),<B>n</B> (nautical
mile), <B>i</B> (inch), <B>c</B> (cm), or <B>p</B> (points). Without
<B>-F</B>, the output (or input, see <B>-I</B>) are in the units
specified by MEASURE_UNIT (but see <B>-D</B>).
<B>-H</B> Input file(s) has Header record(s). Number of
header records can be changed by editing your .gmt
defaults file. If used, <B><A HREF="GMT.html">GMT</A></B> default is 1 header
record.
<B>-I</B> Do the Inverse transformation, i.e. get (longi
tude,latitude) from (x,y) data.
<B>-M</B> Multiple segment file(s). Segments are separated by
a special record. For ASCII files the first char
acter must be <I>flag</I> [Default is '>']. For binary
files all fields must be NaN.
<B>-S</B> Suppress points that fall outside the region.
<B>-V</B> Selects verbose mode, which will send progress
reports to stderr [Default runs "silently"].
tude,longitude) input/output. [Default is (longi
tude,latitude)]. Applies to geographic coordinates
only.
<B>-bi</B> Selects binary input. Append <B>s</B> for single precision
[Default is double]. Append <I>n</I> for the number of
columns in the binary file(s). [Default is 2 input
columns]
<B>-bo</B> Selects binary output. Append <B>s</B> for single preci
sion [Default is double].
</PRE>
<H2>EXAMPLES</H2><PRE>
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
mapproject lonlatfile <B>-R</B>20/50/12/25 <B>-Jm</B>0.5<B>c</B> > xyfile
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
mapproject tracks.* <B>-R</B>-80/-70/20/40 <B>-Jt</B>-75/1:500000 <B>-:</B> <B>-S</B>
<B>-Di</B> <B>-bo</B> <B>-bi</B><I>2</I> > tmfile.b
</PRE>
<H2>RESTRICTIONS</H2><PRE>
The rectangular input region set with <B>-R</B> will in general
be mapped into a non-rectangular grid. Unless <B>-C</B> 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
<B>mapproject</B> 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 transforma
tion work correctly, or alternatively, use <I>awk</I> to scale
and shift the (x,y) values before transforming.
</PRE>
<H2>ELLIPSOIDS AND SPHEROIDS</H2><PRE>
GMT will use ellipsoidal formulae if they are implemented
and the user have selected an ellipsoid as the reference
shape (see gmtdefaults). 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 auxillary latitudes) for
larger maps. The ellipsoidal formulae are used are fol
lows: (a) Transverse Mercator: When all points are within
10 degrees of central meridian, (b) Conic projections when
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 <A HREF="GMT.html">GMT</A>
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 exam
ples 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 <A HREF="GMT.html">GMT</A>
uses), while Snyder rounds off and uses 0.00676866. This
difference can give discrepancies of several 10 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.
</PRE>
<H2>SEE ALSO</H2><PRE>
<I><A HREF="gmtdefaults.html">gmtdefaults</A></I>(l), <I>gmt</I>(l), <I><A HREF="project.html">project</A></I>(l)
</PRE>
<H2>REFERENCES</H2><PRE>
Snyder, J. P., 1987, Map Projections - A Working Manual,
U.S. Geological Survey Prof. Paper 1395.
</PRE>
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