img2google
img2google - Create Google Earth KML overlay tiles from bathymetry
Mercator img grid
Synopsis
img2google
-Rregion
[ imgfile ]
[ -Amode[altitude] ]
[ -C ]
[ -Ffademin/fademax ]
[ -Gprefix ]
[ -LLODmin/LODmax ]
[ -Nlayername ]
[ -Tdoctitle ]
[ -UURL ]
[ -V[level] ]
[ -Z ]
Description
img2google is a shell script that reads a 1x1 minute Mercator surface relief img file and
creates a Google Earth overlay KML file and associated PNG tile for the
specified region. If no input file is given we use topo.18.1.img.
- -R[unit]west/east/south/north[/zmin/zmax][r]
- west, east, south, and north specify the region of interest,
and you may specify them in decimal degrees or in
[+-]dd:mm[:ss.xxx][W|E|S|N] format. Append r if lower left
and upper right map coordinates are given instead of w/e/s/n. The
two shorthands -Rg and -Rd stand for global domain (0/360
and -180/+180 in longitude respectively, with -90/+90 in latitude).
Alternatively for grid creation, give Rcodelon/lat/nx/ny, where
code is a 2-character combination of L, C, R (for left, center, or right)
and T, M, B for top, middle, or bottom. e.g., BL for lower left. This
indicates which point on a rectangular region the lon/lat coordinate
refers to, and the grid dimensions nx and ny with grid spacings via
-I is used to create the corresponding region.
Alternatively, specify the name of an existing grid file and the
-R settings (and grid spacing, if applicable) are copied from
the grid. Using -Runit expects projected (Cartesian)
coordinates compatible with chosen -J and we inversely project
to determine actual rectangular geographic region.
For perspective view (-p), optionally append /zmin/zmax.
In case of perspective view (-p), a z-range (zmin, zmax)
can be appended to indicate the third dimension. This needs to be
done only when using the -Jz option, not when using only the
-p option. In the latter case a perspective view of the plane is
plotted, with no third dimension.
Options
- imgfile
- An img format bathymetry/topography file such as those created by
Sandwell and Smith. If this files does not exist in the current
directory and the user has set the environment variable
$GMT_DATADIR, then img2grd will try
to find imgfile in $GMT_DATADIR.
- -A
- Selects one of 5 altitude modes recognized by Google Earth that
determines the altitude (in m) of the image: G clamped to the
ground, g append altitude relative to ground, a append absolute
altitude, s append altitude relative to seafloor, and S clamp it
to the seafloor [Default].
- -C
- Turn on clipping so that only portions below sea level will be visible
in the image [no clipping].
- -F
- Sets the distance over which the geometry fades, from fully opaque to
fully transparent. These ramp values, expressed in screen pixels, are
applied at the minimum and maximum end of the LOD (visibility) limits,
respectively. [no fading (0/0)].
- -G
- Specify the prefix for the output image file (the extensions are set
automatically). Default uses the naming
topoN|S<north>E|W<west>.
- -L
- Measurement in screen pixels that represents the minimum limit of the
visibility range for a given Region Google Earth calculates the size of
the Region when projected onto screen space. Then it computes the square
root of the Region’s area (if, for example, the Region is square and the
viewpoint is directly above the Region, and the Region is not tilted,
this measurement is equal to the width of the projected Region). If this
measurement falls within the limits defined by LODmin and LODmax
(and if the region is in view), the Region is active. If this limit is
not reached, the associated geometry is considered to be too far from
the user’s viewpoint to be drawn. LODmax represents the maximum limit
of the visibility range for a given Region. A value of 1, the default,
indicates “active to infinite size.” [always active].
- -N
- Append the layername of the image (use quotes if strings contain spaces)
[topoN|S<north>E|W<west>].
- -T
- Append the document title (use quotes if strings contain spaces)
[“Predicted bathymetry”].
- -U
- By default, images are referenced locally relative to the KML file.
Specify an URL to prepend a server address to the image name reference
[local].
- -V[level] (more ...)
- Select verbosity level [c].
- -Z
- Uses zip (which must be installed) to create a *.kmz file for easy
distribution; append + to delete the KML and PNG file after zipping
[No zipping].
Examples
To create a 10x10 degree Google Earth KML tile for the region
-R170/180/20/30 using the default topo.18.1.img and output
naming convention, try
img2google -R170/180/20/30
To make the same tile with a previous file such as topo.15.1.img, run in verbose
mode, clip so only oceanic areas are visible, name the output oldimage,
specify the KML metadata directly (including setting the image altitude
to 10 km), and make a single *.kmz file, try
img2google topo.15.1.img -R170/180/20/30 -Aa10000 -C -Goldimage \
-N"My KML title" -T"My KML title" -Uhttp://my.server.com/images -V -Z
DATA SETS
For topo.18.1.img and other Sandwell/Smith altimetry-derived Mercator
grids, visit http://topex.ucsd.edu.