GTOPO30 is a global digital elevation model
(DEM) with a horizontal grid spacing of 30 arc seconds
(approximately 1 kilometer). It covers the full extent of latitude
from 90 degrees south to 90 degrees north, and the full extent of
longitude from 180 degrees west to 180 degrees east. The vertical
units represent elevation in meters above mean sea level. In the
DEM, ocean areas have been masked as "no data" and have been
assigned a value of -9999.
A full sample of a GTOPO30 database can be downloaded from: http://edcdaac.usgs.gov/gtopo30/gtopo30.asp.
The source code for the Map Builder demonstration, which contains
all of the code described in this section, can be found at <installdir> /jviews-maps810/samples/mapbuilder/index.html.
The IlvGTopo30Reader class is a file reader that
creates reprojectable, stylable and pixel-on-demand images that
can provide altitude data.
To create images:
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First create an image reader and add the image file you want to be read:
IlvGTopo30Reader imageReader = new IlvGTopo30Reader(); imageReader.addMap(gtopoFile);
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Create a data source and link it with the manager properties by inserting it into the data source tree:
IlvMapDataSource imageDataSource = IlvRasterDataSourceFactory. buildTiledImageDataSource(manager,imageReader,true,true,null); IlvMapDataSourceModel dataSourceModel = IlvMapDataSourceProperty.GetMapDataSourceModel(manager); dataSourceModel.insert(imageDataSource);
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Start reading your data:
dataSourceModel.start();
Starting the data source creates the necessary tiled layers, tile
managers and IlvRasterIcon instances to manage the
pixel-on-demand feature and the progressive display of the
geo-referenced image.
This icon associates altitude properties that can be used as
altitude data sources, see Using the altitude provider property.