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NAME

       m.proj  - Converts coordinates from one projection to another (cs2cs frontend).

KEYWORDS

       miscellaneous, projection, transformation

SYNOPSIS

       m.proj
       m.proj --help
       m.proj      [-iodec]       [coordinates=east,north]       [input=name]       [output=name]
       [separator=character]    [proj_in=string]    [proj_out=string]    [--overwrite]   [--help]
       [--verbose]  [--quiet]  [--ui]

   Flags:
       -i
           Use LL WGS84 as input and current location as output projection

       -o
           Use current location as input and LL WGS84 as output projection

       -d
           Output long/lat in decimal degrees, or other projections with many decimal places

       -e
           Include input coordinates in output file

       -c
           Include column names in output file

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       coordinates=east,north
           Input coordinates to reproject

       input=name
           Name of input coordinate file
           ’-’ for standard input

       output=name
           Name for output coordinate file (omit to send to stdout)

       separator=character
           Field separator (format: input[,output])
           Special characters: pipe, comma, space, tab, newline
           Default: pipe

       proj_in=string
           Input projection parameters (PROJ.4 style)

       proj_out=string
           Output projection parameters (PROJ.4 style)

DESCRIPTION

       This  program  allows  a  user  to  convert  coordinates  from  one projection to another.
       Coordinates can be read from one file, converted, and results  written  to  another  file.
       Alternatively,  if  the  input=-,  eastings  and  northings  may  be passed to the program
       directly from standard input. If the output  option  is  omitted,  the  results  are  sent
       directly  to  standard  output. In this way m.proj can be used as a simple frontend to the
       PROJ.4 cs2cs utility. The -i or -o flags make the task  especially  easy  for  the  common
       problem of converting to or from lat/long WGS84.

       Note:  This  program  does  not  transform  GRASS  maps,  it  is designed to determine the
       equivalent coordinate values of an individual position or list of positions. Use v.proj to
       reproject vector maps or r.proj for raster maps.

NOTES

       cs2cs  expects  input data to formatted as x y, so if working with latitude-longitude data
       be sure to send the x value first, i.e., longitude latitude. Output data will be  exported
       using the same convention.

       cs2cs  will  treat  a third data column as a z value (elevation) and will modify the value
       accordingly. This usually translates into small but real differences in that data column.

       cs2cs does not expect the input stream to contain column headings, only numbers.  If  your
       data  file  has  lines  you wish to have passed through without being processed, they must
       start with the ’#’ character.

       If sending m.proj data from standard input, be aware that the data is first  stored  to  a
       temporary  file  before being processed with cs2cs.  It is therefore not advisable to send
       m.proj data from an open data stream. The module will stop  listening  for  incoming  data
       after 2 seconds of inactivity. You may use the projection parameters gleaned from m.proj’s
       verbose mode (--verbose) with cs2cs directly in this case.

       Custom projection parameters can be used  via  the  proj_in  and  proj_out  options.  Full
       documentation of the projection parameter format may be found on the PROJ.4 website. Using
       these options will fully override the default parameters the module would normally use.

       By using the --verbose verbose flag, the user can see exactly what  projection  parameters
       will be used in the conversion as well as some other informative messages.

       If  output  is to lat/long, it will be formatted using PROJ.4’s Degree:Minute:Second (DMS)
       convention of DDDdMM’SSS.SS"H. This can be handy if you wish to quickly  convert  lat/long
       decimal degree data into its DMS equivalent.
       Alternatively,  to  have m.proj output data in decimal degrees, use the -d flag. This flag
       can also be used with non-lat/long data to force a higher number of  decimal  places  (the
       cs2cs default is 2).

       Note  that Lat/long output can be converted to GRASS’s DMS convention (DDD:MM:SSS.SSSH) by
       piping the results of m.proj through the sed stream editor as follows.
       m.proj -o ... | sed -e ’s/d/:/g’ -e "s/’/:/g"  -e ’s/"//g’

EXAMPLES

       The examples are suitable for the North Carolina sample dataset if not stated otherwise:

   Reproject vector point coordinate pairs to Long/Lat WGS84
       The m.proj module is designed to work seamlessly with point data  exported  from  the  GIS
       with v.out.ascii, as the following example shows.
       # Long/Lat WGS84 output in DMS
       v.out.ascii bridges | m.proj -o input=-
       # Long/Lat WGS84 output in decimal degree
       v.out.ascii bridges | m.proj -o -d input=-

   Reproject Long/Lat WGS84 coordinate pair to current map projection
       To  convert  a  Long/Lat  WGS84 coordinate pair to the current map projection using the -i
       flag which sets the target projection parameters automatically from the  current  location
       definition:
       echo "-78.61168178 33.92225767" | m.proj -i input=-
       645513.47|19180.31|0.00

       The  same,  but  load points from a file named waypoints.txt and continue on to import the
       results into a GRASS vector points map in the current map projection:
       # check file content
       cat waypoints.txt
       -78.43977824 33.89587173
       -78.54944691 33.88964566
       -78.51078074 33.88141495
       -77.14037951 35.60543020
       # reproject points and generate vector map on the fly
       m.proj -i input=waypoints.txt | v.in.ascii input=- output=test_pnts
       # verify result
       v.db.select test_pnts cat|dbl_1|dbl_2|dbl_3
       1|661427.74|16329.14|0
       2|651285.43|15586.79|0
       3|654867.21|14690.64|0
       4|778074.58|207402.6|0

   Custom projection parameter usage
       To transform points from  a  UTM  projection  (here  specified  with  detailed  projection
       definition  rather  than  using an EPSG code) into the Gauss-Krüger Grid System, importing
       from and exporting to files:
       m.proj proj_in="+proj=utm +name=utm +a=6378137.0 +es=0.006694380 \
           +zone=32 +unfact=1.0" proj_out="+proj=tmerc +name=tmerc \
           +a=6377397.155 +es=0.0066743720 +lat_0=0.0 +lon_0=9.0 +k=1.0 \
           +x_0=3500000.0" input=utm.coord.txt output=new.gk.coord.txt

       Projection  parameters  provided  in  the  above  case:  +proj  (projection  type),  +name
       (projection  name),  +a  (ellipsoid:  equatorial  radius),  +es  (ellipsoid:  eccentricity
       squared), +zone (zone for the area), +unfact  (conversion  factor  from  meters  to  other
       units,  e.g.  feet),  +lat_0  (standard  parallel),  +lon_0  (central meridian), +k (scale
       factor) and +x_0 (false easting). Sometimes false northing is needed  which  is  coded  as
       +y_0.  Internally, the underlying PROJ.4 projection library performs an inverse projection
       to latitude-longitude and then projects the coordinate list to the target projection.

       Datum conversions are automatically handled by the PROJ.4 library if  +datum  setings  are
       specified  on  both  the  input  and  output projections on the command line. The +towgs84
       parameter can be used  to  define  either  3  or  7  term  datum  transform  coefficients,
       satisfying this requirement.

       If  a  datum  is specified there is no need for the +ellps= or underlying parameters, +a=,
       +es=, etc.

       Another custom parameter usage example:
       m.proj proj_in="+proj=tmerc +datum=ire65 +lat_0=53.5 +lon_0=-8 +x_0=200000 \
           +y_0=250000 +k=1.000035" proj_out="+proj=ll +datum=wgs84" input=wpt.txt
       or without datum transformation:
       m.proj proj_in="+proj=tmerc +ellps=modif_airy +lat_0=53.5 +lon_0=-8 +x_0=200000 \
           +y_0=250000 +k=1.000035" proj_out="+proj=ll +datum=wgs84" input=wpt.txt

       In this example no datum transformation will take place as a datum was not  specified  for
       the  input projection. The datum specified for the output projection will thus be silently
       ignored and may be left out; all that is achieved a simple conversion  from  projected  to
       geodetic co-ordinates, keeping the same datum (and thus also the same ellipsoid).

       For more usage examples, see the documentation for the PROJ.4 cs2cs program.

REFERENCES

           ·   Evenden,  G.I.  (1990) Cartographic projection procedures for the UNIX environment
               - a user’s manual.  USGS Open-File Report 90-284 (OF90-284.pdf)  See  also  there:
               Interim Report and 2nd Interim Report on Release 4, Evenden 1994).

           ·   PROJ.4 Cartographic Projection Library

SEE ALSO

        g.proj, r.proj, v.proj, i.rectify, v.in.ascii, v.out.ascii

AUTHOR

       M. Hamish Bowman, Dept. Marine Science, Otago University, New Zealand
       Functionality inspired by the m.proj and m.proj2 modules for GRASS GIS 5.

       Last changed: $Date: 2017-08-16 08:58:03 +0200 (Wed, 16 Aug 2017) $

SOURCE CODE

       Available at: m.proj source code (history)

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