1m.proj(1) Grass User's Manual m.proj(1)
2
6 m.proj - Convert coordinates from one projection to another (cs2cs
7 frontend).
8
10 miscellaneous, projection
11
13 m.proj
14 m.proj help
15 m.proj [-iodv] [input=filename] [output=filename] [fs=character]
16 [proj_in=string] [proj_out=string]
17 Flags:
19 -i Use LL WGS84 as input and current location as output projection
20 -o Use current location as input and LL WGS84 as output projection
22 -d Output long/lat in decimal degrees or other projections with many
24 decimal places
25 -v Verbose mode (print projection parameters and filenames to stderr)
27 Parameters:
29 input=filename
30 Input coordinate file (omit to read from stdin)
31 output=filename
33 Output coordinate file (omit to send to stdout)
34 fs=character
36 Field separator Default: |
37 proj_in=string
39 Input projection parameters (PROJ.4 style)
40 proj_out=string
42 Output projection parameters (PROJ.4 style)
43
45 This program allows a user to convert coordinates from one projection
46 to another. Coordinates can be read from one file, converted, and
47 results written to another file. Alternatively, if the input and/or
48 output options are omitted, eastings and northings may be passed to the
49 program directly from stdin and results sent directly to stdout. In
50 this way m.proj can be used as a simple frontend to the PROJ.4 cs2cs
51 utility. The -i or -o flags make the task especially easy for the com‐
52 mon problem of converting to or from lat/long WGS84.
53 Note: This program does not transform GRASS maps, it is designed to
55 determine the equivalent coordinate values of an individual position or
56 list of positions. Use v.proj or r.proj to reproject GRASS maps.
57
59 cs2cs expects input data to formatted as "x y", so if working with lat‐
60 itude-longitude data be sure to send the x value first, i.e., "longi‐
61 tude latitude". Output data will be exported using the same convention.
62 cs2cs will treat a third data column as a z value (elevation) and will
64 modify the value accordingly. This usually translates into small but
65 real differences in that data column.
66 cs2cs does not expect the input stream to contain column headings, only
68 numbers. If your data file has lines you wish to have passed through
69 without being processed, they must start with the '#' character.
70 If sending m.proj data from stdin, be aware that the data is first
72 stored to a temporary file before being processed with cs2cs. It is
73 therefore not advisable to send m.proj data from an open data stream.
74 The module will stop listening for incoming data after 2 seconds of
75 inactivity. You may use the projection parameters gleaned from m.proj's
76 verbose mode (-v) with cs2cs directly in this case.
77 Custom projection parameters can be used via the proj_in and proj_out
79 options. Full documentation of the projection parameter format may be
80 found on the PROJ.4 website. Using these options will fully override
81 the default parameters the module would normally use.
82 By using the -v verbose flag, the user can see exactly what projection
84 parameters will be used in the conversion as well as some other infor‐
85 mative messages.
86 If output is to lat/long, it will be formatted using PROJ.4's
88 Degree:Minute:Second (DMS) convention of DDDdMM'SSS.SS"H. This can be
89 handy if you wish to quickly convert lat/long decimal degree data into
90 its DMS equivalent.
91 Alternatively, to have m.proj output data in decimal degrees, use the
92 -d flag. This flag can also be used with non-lat/long data to force a
93 higher number of decimal places (the cs2cs default is 2).
94 Lat/long output can be converted to GRASS's DMS convention
96 (DDD:MM:SSS.SSSH) by piping the results of m.proj through the sed
97 stream editor as follows.
98 m.proj -o | sed -e 's/d/:/g' -e "s/'/:/g" -e 's/"//g'
99 The m.proj module is designed to work seamlessly with point data
102 exported from the GIS with v.out.ascii, as the following example shows.
103 v.out.ascii bugsites | m.proj -o
104
107 To convert a WGS84 long/lat coordinate to the current map projection
108 using the -i flag to set projection parameters automaticlly:
109 GRASS> echo "170.510125 -45.868537" | m.proj -i
110 2316541.70 5479193.51 1.23
111 The same, but load points from a file named "waypoints.txt" and con‐
114 tinue on to import the results into a GRASS vector points map in the
115 current map projection:
116 m.proj -i in=waypoints.txt | cut -f1 -d' ' | v.in.ascii out=test_pt
117 fs=tab
118 Here the standard UNIX cut tool is used to discard the z residual.
119 To convert all coordinates from a vector points map in the current pro‐
121 jection to WGS84 long/lat, with output in decimal form:
122 v.out.ascii bugsites | m.proj -od
123 To transform points from a UTM projection into the Gauss-Krüger Grid
126 System, importing and exporting to files:
127 m.proj proj_in="+proj=utm +name=utm +a=6378137.0 +es=0.006694380 \
128 +zone=32 +unfact=1.0" proj_out="+proj=tmerc +name=tmerc \
129 +a=6377397.155 +es=0.0066743720 +lat_0=0.0 +lon_0=9.0 +k=1.0 \
130 +x_0=3500000.0" input=utm.coord.txt output=new.gk.coord.txt
131 Projection parameters provided in the above case: "+proj" (projection
134 type), "+name" (projection name), "+a" (ellipsoid: equatorial radius),
135 "+es" (ellipsoid: eccentricity squared), "+zone" (zone for the area),
136 "+unfact" (conversion factor from meters to other units, e.g. feet),
137 "+lat_0" (standard parallel), "+lon_0" (central meridian), "+k" (scale
138 factor) and "+x_0" (false easting). Sometimes false northing is needed
139 which is coded as "+y_0". Internally, the underlying PROJ.4 projection
140 library performs an inverse projection to latitude-longitude and then
141 projects the coordinate list to the target projection.
142 Datum conversions are automatically handled by the PROJ.4 library if
144 "+datum" setings are specified on both the input and output projections
145 on the command line. The "+towgs84" parameter can be used to define
146 either 3 or 7 term datum transform coefficients, satisfying this
147 requirement.
148 If a datum is specified there is no need for the '+ellps=' or underly‐
150 ing parameters, '+a=', '+es=', etc.
151 Another custom parameter usage example:
153 m.proj proj_in="+proj=tmerc +datum=ire65 +lat_0=53.5 +lon_0=-8
155 +x_0=200000 \
156 +y_0=250000 +k=1.000035" proj_out="+proj=ll +datum=wgs84"
157 input=wpt.txt
158 or without datum transformation:
159 m.proj proj_in="+proj=tmerc +ellps=modif_airy +lat_0=53.5 +lon_0=-8
160 +x_0=200000 \
161 +y_0=250000 +k=1.000035" proj_out="+proj=ll +datum=wgs84"
162 input=wpt.txt
163 In this example no datum transformation will take place as a datum was
166 not specified for the input projection. The datum specified for the
167 output projection will thus be silently ignored and may be left out;
168 all that is achieved a simple conversion from projected to geodetic co-
169 ordinates, keeping the same datum (and thus also the same ellipsoid).
170 For more usage examples, see the documentation for the PROJ.4 cs2cs
172 program.
173
175 [1] Evenden, G.I. (1990) Cartographic projection procedures for the
176 UNIX environment - a user's manual. USGS Open-File Report 90-284
177 (OF90-284.pdf) See also there: Interim Report and 2nd Interim Report on
178 Release 4, Evenden 1994).
179 [2] PROJ.4 Cartographic Projection Library
181
183 v.proj, r.proj, g.proj, g.setproj, i.rectify, v.in.ascii, v.out.ascii
184
186 M. Hamish Bowman, Dept. Marine Science, Otago University, New Zealand
187 Functionality inspired by the m.proj and m.proj2 modules for GRASS GIS
188 5.
189 Last changed: $Date: 2006/08/31 08:47:06 $
191 Full index
193GRASS 6.2.2 m.proj(1)