Provided by: gmt-common_5.4.5+dfsg-1_all

**NAME**

project - Project table data onto lines or great circles, generate tracks, or translate coordinates

**SYNOPSIS**

project[table]-Ccx/cy[-Aazimuth] [-Ebx/by] [-Fflags] [-Gdist[/colat][+h] ] [-L[w][l_min/l_max] ] [-N] [-Q] [-S] [-Tpx/py] [-V[level] ] [-Ww_min/w_max] [-bbinary ] [-dnodata ] [-eregexp ] [-fflags ] [-ggaps ] [-hheaders ] [-iflags ] [-sflags ] [-:[i|o] ]Note:No space is allowed between the option flag and the associated arguments.

**DESCRIPTION**

projectreads arbitrary (x,y[,z]) data from standard input [ortable] and writes to standard output any combination of (x,y,z,p,q,r,s), where (p,q) are the coordinates in the projection, (r,s) is the position in the (x,y) coordinate system of the point on the profile (q= 0 path) closest to (x,y), andzis all remaining columns in the input (beyond the requiredxandycolumns). Alternatively,projectmay be used to generate (r,s,p) triples at equal incrementsdistalong a profile. In this case (-Goption), no input is read. Projections are defined in any (but only) one of three ways: (Definition 1) By a Center-Cand an Azimuth-Ain degrees clockwise from North. (Definition 2) By a Center-Cand end point E of the projection path-E. (Definition 3) By a Center-Cand a roTation pole position-T. To spherically project data along a great circle path, an oblique coordinate system is created which has its equator along that path, and the zero meridian through the Center. Then the oblique longitude (p) corresponds to the distance from the Center along the great circle, and the oblique latitude (q) corresponds to the distance perpendicular to the great circle path. When moving in the increasing (p) direction, (towardBor in theazimuthdirection), the positive (q) direction is to your left. If a Pole has been specified, then the positive (q) direction is toward the pole. To specify an oblique projection, use the-Toption to set the Pole. Then the equator of the projection is already determined and the-Coption is used to locate thep= 0 meridian. The Centercx/cywill be taken as a point through which thep= 0 meridian passes. If you do not care to choose a particular point, use the South pole (ox= 0,oy= -90). Data can be selectively windowed by using the-Land-Woptions. If-Wis used, the projection Width is set to use only points withw_min< q <w_max. If-Lis set, then the Length is set to use only those points withl_min< p <l_max. If the-Eoption has been used to define the projection, then-Lwmay be selected to window the length of the projection to exactly the span fromOtoB. Flat Earth (Cartesian) coordinate transformations can also be made. Set-Nand remember thatazimuthis clockwise from North (theyaxis), NOT the usual cartesian theta, which is counterclockwise from thexaxis.azimuth= 90 - theta. No assumptions are made regarding the units forx,y,r,s,p,q,dist,l_min,l_max,w_min,w_max. If-Qis selected, map units are assumed andx,y,r,smust be in degrees andp,q,dist,l_min,l_max,w_min,w_maxwill be in km. Calculations of specific great-circle and geodesic distances or for back-azimuths or azimuths are better done using mapproject.projectis CASE SENSITIVE. Use UPPER CASE for all one-letter designators which begin optional arguments. Use lower case for the xyzpqrs letters in-flags.

**REQUIRED** **ARGUMENTS**

-Ccx/cycx/cysets the origin of the projection, in Definition 1 or 2. If Definition 3 is used (-T), thencx/cyare the coordinates of a point through which the oblique zero meridian (p= 0) should pass. Thecx/cyis not required to be 90 degrees from the pole.

**OPTIONAL** **ARGUMENTS**

tableOne or more ASCII (or binary, see-bi[ncols][type]) data table file(s) holding a number of data columns. If no tables are given then we read from standard input.-Aazimuthazimuthdefines the azimuth of the projection (Definition 1).-Ebx/bybx/bydefines the end point of the projection path (Definition 2).-FflagsSpecify your desired output using any combination ofxyzpqrs, in any order. Do not space between the letters. Use lower case. The output will be ASCII (or binary, see-bo) columns of values corresponding toxyzpqrs[Default]. If both input and output are using ASCII format then thezdata are treated as textstring(s). If the-Goption is selected, the output will bersp.-Gdist[/colat][+h] Generate mode. No input is read. Create (r,s,p) output points everydistunits ofp. See-Qoption. Alternatively, append/colatfor a small circle instead [Default is a colatitude of 90, i.e., a great circle]. Use-Cand-Eto generate a circle that goes through the center and end point. Note, in this case the center and end point cannot be farther apart than 2*|colat|. Finally, if you append+hthe we will report the position of the pole as part of the segment header [no header].-L[w][l_min/l_max] Length controls. Project only those points whosepcoordinate is withinl_min<p<l_max. If-Ehas been set, then you may use-Lwto stay within the distance fromCtoE.-NFlat Earth. Make a Cartesian coordinate transformation in the plane. [Default uses spherical trigonometry.]-QMap type units, i.e., project assumesx,y,r,sare in degrees whilep,q,dist,l_min,l_max,w_min,w_maxare in km. If-Qis not set, then all these are assumed to be in the same units.-SSort the output into increasingporder. Useful when projecting random data into a sequential profile.-Tpx/pypx/pysets the position of the rotation pole of the projection. (Definition 3).-V[level] (more ...) Select verbosity level [c].-Ww_min/w_maxWidth controls. Project only those points whoseqcoordinate is withinw_min<q<w_max.-bi[ncols][t] (more ...) Select native binary input. [Default is 2 input columns].-bo[ncols][type] (more ...) Select native binary output. [Default is given by-For-G].-d[i|o]nodata(more ...) Replace input columns that equalnodatawith NaN and do the reverse on output.-e[~]"pattern"|-e[~]/regexp/[i] (more ...) Only accept data records that match the given pattern.-f[i|o]colinfo(more ...) Specify data types of input and/or output columns.-g[a]x|y|d|X|Y|D|[col]z[+|-]gap[u] (more ...) Determine data gaps and line breaks.-h[i|o][n][+c][+d][+rremark][+rtitle] (more ...) Skip or produce header record(s).-icols[+l][+sscale][+ooffset][,...] (more ...) Select input columns and transformations (0 is first column).-s[cols][a|r] (more ...) Set handling of NaN records.-:[i|o] (more ...) Swap 1st and 2nd column on input and/or output.-^or just-Print a short message about the syntax of the command, then exits (NOTE: on Windows just use-).-+or just+Print an extensive usage (help) message, including the explanation of any module-specific option (but not the GMT common options), then exits.-?or no arguments Print a complete usage (help) message, including the explanation of all options, then exits.

**ASCII** **FORMAT** **PRECISION**

The ASCII output formats of numerical data are controlled by parameters in your gmt.conf file. Longitude and latitude are formatted according to FORMAT_GEO_OUT, absolute time is under the control of FORMAT_DATE_OUT and FORMAT_CLOCK_OUT, whereas general floating point values are formatted according to FORMAT_FLOAT_OUT. Be aware that the format in effect can lead to loss of precision in ASCII output, which can lead to various problems downstream. If you find the output is not written with enough precision, consider switching to binary output (-boif available) or specify more decimals using the FORMAT_FLOAT_OUT setting.

**EXAMPLES**

To generate points every 10km along a great circle from 10N,50W to 30N,10W: gmt project -C-50/10 -E-10/30 -G10 -Q > great_circle_points.xyp (Note that great_circle_points.xyp could now be used as input for grdtrack, etc. ). To generate points every 1 degree along a great circle from 30N,10W with azimuth 30 and covering a full 360, try: gmt project -C10W/30N -A30 -G1 -L-180/180 > great_circle.txt To generate points every 10km along a small circle of colatitude 60 from 10N,50W to 30N,10W: gmt project -C-50/10 -E-10/30 -G10/60 -Q > small_circle_points.xyp To create a partial small circle of colatitude 80 about a pole at 40E,85N, with extent of 45 degrees to either side of the meridian defined by the great circle from the pole to a point 15E,15N, try gmt project -C15/15 -T40/85 -G1/80 -L-45/45 > some_circle.xyp To project the shiptrack gravity, magnetics, and bathymetry in c2610.xygmb along a great circle through an origin at 30S, 30W, the great circle having an azimuth of N20W at the origin, keeping only the data from NE of the profile and within +/- 500 km of the origin, run: gmt project c2610.xygmb -C-30/-30 -A-20 -W-10000/0 -L-500/500 -Fpz -Q > c2610_projected.pgmb (Note in this example that-W-10000/0 is used to admit any value with a large negativeqcoordinate. This will take those points which are on our right as we walk along the great circle path, or to the NE in this example.) To make a Cartesian coordinate transformation of mydata.xy so that the new origin is at 5,3 and the newxaxis (p) makes an angle of 20 degrees with the oldxaxis, use: gmt project mydata.xy -C5/3 -A70 -Fpq > mydata.pq To take data in the file pacific.lonlat and transform it into oblique coordinates using a pole from the hotspot reference frame and placing the oblique zero meridian (p= 0 line) through Tahiti, run: gmt project pacific.lonlat -T-75/68 -C-149:26/-17:37 -Fpq > pacific.pq Suppose that pacific_topo.nc is a grid file of bathymetry, and you want to make a file of flowlines in the hotspot reference frame. If you run: gmt grd2xyz pacific_topo.nc | project -T-75/68 -C0/-90 -Fxyq | xyz2grd -Retc -Ietc -Cflow.nc then flow.nc is a file in the same area as pacific_topo.nc, but flow contains the latitudes about the pole of the projection. You now can use grdcontour on flow.nc to draw lines of constant oblique latitude, which are flow lines in the hotspot frame. If you have an arbitrarily rotation polepx/pyand you would like to draw an oblique small circle on a map, you will first need to make a file with the oblique coordinates for the small circle (i.e., lon = 0-360, lat is constant), then create a file with two records: the north pole (0/90) and the origin (0/0), and find what their oblique coordinates are using your rotation pole. Now, use the projected North pole and origin coordinates as the rotation pole and center, respectively, and project your file as in the pacific example above. This gives coordinates for an oblique small circle.

**SEE** **ALSO**

fitcircle, gmt, gmtvector, grdtrack, mapproject, grdproject, grdtrack

**COPYRIGHT**

2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe