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Process
Creating Bathymetric/Topographic grids.
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- Create a subset of etopo2 data for an atlas area.
- For areas crossing the -180 / 180 boundary grids, subset data from each side of the boundary.
- The global grid is not projected or subset and is maintained in the geographic coordinate
system as distributed.
- For the four hemisphere grids and the two polar areas grids project them into an
orthographic projection.
- Set the latitude of origin to:
- 90 for the northern hemisphere
- -90 for the southern hemisphere
- 0 for the east and west hemispheres
- Set the central meridian to:
- 0 for the southern hemisphere
- 180 for the northern hemisphere
- 90 for the eastern hemisphere
- -90 for the western hemisphere
- Project all other grids into a Mercator projection.
- Use a latitude of true scale centered on the area
- Use the central meridian centered on the area
- For areas crossing the -180/180 bourndary, merge the sub-grids.
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Creating of sun shaded images from grids.
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- Use the MB-System software package
(
http://www.ldeo.columbia.edu/MB-System/
),
specifically the "mbm_grdtiff" command.
- Create background GeoTIFF's
(
http://remotesensing.org/geotiff/spec/contents.html
)
for each grid.
- For the InfoBank Atlas grids are all created:
- in the same projection and resolution
(1 image pixel for each grid cell)
- with vertical exaggeration of 3x
- an apparent light direction (sun-shading) of 300 degrees.
- using the sea_land color bar (units of meters above/below sea level)
- The InfoBank Atlas background GeoTIFF images are available for downloading
as .zip files from the atlas web pages
(
http://walrus.wr.usgs.gov/infobank/programs/html/main/atlas.html
)
- Each .zip file contains
- the GeoTiff
- a Projection Description file
- a World File
Example World File
| Data Value |
Description |
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5.000000000000
|
size of pixel in x direction
|
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0.000000000000
|
rotation term for row
|
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0.000000000000
|
rotation term for column
|
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-5.000000000000
|
size of pixel in y direction
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492169.690845528910
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x coordinate of center of upper left pixel in map units
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5426523.318065105000
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y coordinate of center of upper left pixel in map units
|
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Overlaying vector data.
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- Merge a GeoTiff image with other geo-spatial data using ESRI ArcGIS
(
http://www.esri.com/
) software component ArcMap.
- Use ArcMap, the vector data sets such as
shorelines, lakes, rivers, political boundaries, tectonic plate boundaries, and
geographic data from research activities to overlay and symbolize.
- Add a neatline, border, title, and latitude/longitude coordinates to the map and
finally the map is output in:
- a full resolution
- a preset size jpeg image
for distribution on the
InfoBank Atlas
web pages.
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