1g.proj(1) Grass User's Manual g.proj(1)
2
6 g.proj - Prints or modifies GRASS projection information files (in
7 various co-ordinate system descriptions).
8 Can also be used to create new GRASS locations.
9
11 general, projection, create location
12
14 g.proj
15 g.proj --help
16 g.proj [-pgdjfwetc] [georef=file] [wkt=file] [proj4=params]
17 [epsg=code] [datum=name] [datum_trans=index] [location=name]
18 [--help] [--verbose] [--quiet] [--ui]
19 Flags:
21 -p
22 Print projection information in conventional GRASS format
23 -g
25 Print projection information in shell script style
26 -d
28 Verify datum information and print transformation parameters
29 -j
31 Print projection information in PROJ.4 format
32 -f
34 Print ’flat’ output with no linebreaks (applies to WKT and PROJ.4
35 output)
36 -w
38 Print projection information in WKT format
39 -e
41 Use ESRI-style format (applies to WKT output only)
42 -t
44 Force override of datum transformation information in input
45 co-ordinate system
46 -c
48 Modify current location projection files
49 --help
51 Print usage summary
52 --verbose
54 Verbose module output
55 --quiet
57 Quiet module output
58 --ui
60 Force launching GUI dialog
61 Parameters:
63 georef=file
64 Name of georeferenced data file to read projection information from
65 wkt=file
67 Name of ASCII file containing a WKT projection description
68 ’-’ for standard input
69 proj4=params
71 PROJ.4 projection description
72 ’-’ for standard input
73 epsg=code
75 EPSG projection code
76 Options: 1-1000000
77 datum=name
79 Datum (overrides any datum specified in input co-ordinate system)
80 Accepts standard GRASS datum codes, or "list" to list and exit
81 datum_trans=index
83 Index number of datum transform parameters
84 "0" for unspecified or "-1" to list and exit
85 Options: -1-100
86 Default: 0
87 location=name
89 Name of new location to create
90
92 g.proj provides a means of converting a co-ordinate system description
93 (i.e. projection information) between various formats. If compiled
94 without OGR present, the functionality is limited to:
95 · Reporting the projection information for the current location,
97 either in conventional GRASS (-p flag) or PROJ.4 (-j flag) for‐
98 mat
99 · Changing the datum, or reporting and modifying the datum trans‐
101 formation parameters, for the current location
102 When compiled with OGR, functionality is increased and allows output of
104 the projection information in the Well-Known Text (WKT) format popu‐
105 larised by proprietary GIS. In addition, if one of the parameters geo‐
106 ref, wkt, proj4 or epsg is specified, rather than the projection infor‐
107 mation being read from the current location it is imported from an
108 external source as follows:
109 georef=filename
111 g.proj attempts to invoke GDAL and OGR in turn to read a georefer‐
112 enced file filename. The projection information will be read from
113 this file. If the file is not georeferenced or cannot be read, XY
114 (unprojected) will be used.
115 wkt=filename or -
117 The file filename should contain a projection description in WKT
118 format with or without line-breaks (e.g. a ’.prj’ file). If - is
119 given for the filename, the WKT description will be read from stdin
120 rather than a file.
121 proj4=description or -
123 description should be a projection description in PROJ.4 format,
124 enclosed in quotation marks if there are any spaces. If - is given
125 for description, the PROJ.4 description will be read from stdin
126 rather than as a directly-supplied command-line parameter.
127 epsg=number
129 number should correspond to the index number of a valid co-ordinate
130 system in the EPSG database. EPSG code support is based upon a
131 local copy of the GDAL CSV co-ordinate system and datum information
132 files, stored in the directory $GISBASE/etc/proj/ogr_csv. These can
133 be updated if necessary to support future revisions of the EPSG
134 database.
135 If datum information is incorrect or missing in the input co-ordinate
137 system definition (e.g. PROJ.4 descriptions have very limited support
138 for specifying datum names), a GRASS datum abbreviation can instead be
139 supplied using the datum parameter. This will override any datum con‐
140 tained in the input co-ordinate system, and discard any datum transfor‐
141 mation parameters. Enter datum=list to return a list of all the datums
142 supported by GRASS. Since any existing datum transformation parameters
143 will have been discarded, the datumtrans parameter should in general
144 always be used in conjunction with datum.
145 The -p, -j, -w, etc. flags are all functional when importing projection
147 information from an external source, meaning that g.proj can be used to
148 convert between representations of the information. It is not required
149 that either the input or output be in GRASS format.
150 In addition however, if the -c flag is specified, g.proj will create
152 new GRASS projection files (PROJ_INFO, PROJ_UNITS, WIND and
153 DEFAULT_WIND) based on the imported information. If the location param‐
154 eter is specified in addition to -c, then a new location will be cre‐
155 ated. Otherwise the projection information files in the current loca‐
156 tion will be overwritten. The program will not warn before doing this.
157 The final mode of operation of g.proj is to report on the datum infor‐
159 mation and datum transformation parameters associated with the co-ordi‐
160 nate system. The -d flag will report a human-readable summary of this.
161
163 If the input co-ordinate system contains a datum name but no transfor‐
164 mation parameters, and there is more than one suitable parameter set
165 available (according to the files datum.table and datumtransform.table
166 in $GISBASE/etc/proj), g.proj will check the value of the datumtrans
167 option and act according to the following:
168 -1: List available parameter sets in a GUI-parsable (but also
169 human-readable) format and exit.
170 0 (default): Continue without specifying parameters - if used when cre‐
171 ating a location, other GRASS modules will use the "default" (likely
172 non-optimum) parameters for this datum if necessary in the future.
173 Any other number less than or equal to the number of parameter sets
174 available for this datum: Choose this parameter set and add it to the
175 co-ordinate system description.
176 If the -t flag is specified, the module will attempt to change the
177 datum transformation parameters using one of the above two methods even
178 if a valid parameter set is already specified in the input co-ordinate
179 system. This can be useful to change the datum information for an
180 existing location.
181 Output is simply based on the input projection information. g.proj does
183 not attempt to verify that the co-ordinate system thus described
184 matches an existing system in use in the world. In particular, this
185 means there are no EPSG Authority codes in the WKT output.
186 WKT format shows the false eastings and northings in the projected unit
188 (e.g. meters, feet) but in PROJ format it should always be given in
189 meters.
190 The maximum size of input WKT or PROJ.4 projection descriptions is lim‐
192 ited to 8000 bytes.
193
195 Print information
196 Print the projection information for the current location:
197 g.proj -p
198 List the possible datum transformation parameters for the current loca‐
200 tion:
201 g.proj -t datumtrans=-1
202 Create projection (PRJ) file
204 Create a ’.prj’ file in ESRI format corresponding to the current loca‐
205 tion:
206 g.proj -wef > irish_grid.prj
207 Read projection from file
209 Read the projection information from a GeoTIFF file and print it in
210 PROJ.4 format:
211 g.proj -jf georef=ASTER_DEM20020508161837.tif
212 Convert the PROJ.4 projection description contained in a text file to
214 WKT format:
215 cat proj4.description | g.proj -w proj4=-
216 Create new location
218 Create a new location with the co-ordinate system referred to by EPSG
219 code 4326 (Latitude-Longitude/WGS84), without explicitly specifying
220 datum transformation parameters:
221 g.proj -c epsg=4326 location=latlong
222 Create a new location with the co-ordinate system referred to by
224 ESRI-EPSG code 900913 (Google Mercator Projection)
225 g.proj -c epsg=900913 location=google
226 Create a new location with the co-ordinate system referred to by EPSG
228 code 29900 (Irish Grid), selecting datum transformation parameter set
229 no. 2:
230 # list available datums for EPSG code 29900
231 g.proj -t datumtrans=-1 epsg=29900
232 g.proj -c epsg=29900 datumtrans=2 location=irish_grid
233 Create a new location with the same co-ordinate system as the current
235 location, but forcing a change to datum transformation parameter set
236 no. 1:
237 g.proj -c location=newloc -t datumtrans=1
238 Create a new location with the co-ordinate system from a WKT definition
240 stored in a text file:
241 g.proj -c wkt=irish_grid.prj location=irish_grid
242 Create a new location from a PROJ.4 description, explicitly specifying
244 a datum and using the default datum transformation parameters:
245 g.proj -c location=spain proj4="+proj=utm +zone=30 +ellps=intl" datum=eur50 datumtrans=0
246 Using g.proj output for GDAL/OGR tools
248 Reproject external raster map to current GRASS projection (does not
249 always make sense!) using the GDAL ’gdalwarp’ tool. We recommend to
250 use the ERDAS/Img format and not to use the ESRI style of WKT:
251 # example for 30x30 pixel resolution (enforce with -tr to avoid odd values)
252 gdalwarp -of HFA -tr 30 30 -t_srs "`g.proj -wf`" aster.img aster_tmerc.img
253 Reproject external vector map to current GRASS projection using the OGR
255 ’ogr2ogr’ tool:
256 ogr2ogr -t_srs "`g.proj -wf`" polbnda_italy_GB_ovest.shp polbnda_italy_LL.shp
257
259 PROJ 4: Projection/datum support library
260 GDAL raster library and toolset
261 OGR vector library and toolset
262 Further reading
264 · ASPRS Grids and Datum
266 · MapRef - The Collection of Map Projections and Reference Sys‐
268 tems for Europe
269 · Projections Transform List (PROJ4)
271
273 m.proj, r.proj, v.proj, r.import, r.in.gdal, v.import, v.in.ogr
274
276 Paul Kelly
277 Last changed: $Date: 2016-05-28 08:54:25 +0200 (Sat, 28 May 2016) $
279
281 Available at: g.proj source code (history)
282 Main index | General index | Topics index | Keywords index | Graphical
284 index | Full index
285 © 2003-2019 GRASS Development Team, GRASS GIS 7.6.0 Reference Manual
287GRASS 7.6.0 g.proj(1)