Hi Ahmad,
I think the problem is the JAI "fileload" operation which is notorious for
being unable to handle many tif formats. But also, you are doing a lot of
work that GeoTools can do for you.
Here is an example...
File file = ...
GeoTiffReader reader = new GeoTiffReader(file);
GridCoverage2D cov = (GridCoverage2D) reader.read(null);
GridEnvelope gridBounds = cov.getGridGeometry().getGridRange();
System.out.println("grid bounds: " + gridBounds);
Envelope2D worldBounds = cov.getEnvelope2D();
System.out.println("world bounds: " + worldBounds);
int numBands = cov.getNumSampleDimensions();
System.out.println("num bands: " + numBands);
CoordinateReferenceSystem crs = cov.getCoordinateReferenceSystem();
// get the value of the centre location as an example
double[] values = new double[numBands];
double lon = worldBounds.getCenterX();
double lat = worldBounds.getCenterY();
DirectPosition dp = new DirectPosition2D(crs, lon, lat);
cov.evaluate(dp, values);
System.out.println("value at " + dp + " is " + values[0]);
As well as this you can still work directly with the underlying image using
JAI iterators if you want to...
RenderedImage image = cov.getRenderedImage();
If you are using GeoTools 2.5.x you can convert between world coordinates
and grid coordinates like this:
MathTransform2D worldToGrid =
cov.getGridGeometry().getCRSToGrid2D();
Point2D point = new Point2D.Double(lon, lat);
Point2D gridPoint = worldToGrid.transform(point, null);
If you are using GeoTools 2.6-M1 you can do this as well...
GridCoordinates2D gridCoords =
cov.getGridGeometry().worldToGrid(pos);
Hope this helps,
Michael
2009/9/28 Ahmad Al-Obaidy <[email protected]>
> Hi,
>
> How can I read ASTER DEM data set. I have folder that contains tiles of
> ASTER in tif format, and I want to write a function that get lon/lat as
> arguments and return a number as an elevation.
>
> I wrote a class to do that, but I think I have something wrong.
>
> import java.util.concurrent.ConcurrentHashMap;
>
> import javax.media.jai.JAI;
> import javax.media.jai.PlanarImage;
> import javax.media.jai.iterator.RandomIter;
> import javax.media.jai.iterator.RandomIterFactory;
>
> public class AsterDemReader implements DemProvider {
>
> // base path for the tiles
> private String basePath;
>
> // tiles RAM cache
> private ConcurrentHashMap<String, RandomIter> cache = new
> ConcurrentHashMap<String, RandomIter>();
>
> public AsterDemReader(String basePath) {
> this.basePath = basePath;
> }
>
> private RandomIter getTile(String tileName) {
> RandomIter iter = cache.get(tileName);
> if (iter == null) {
> PlanarImage image = JAI.create("fileload", String.format(
> "%s/ASTGTM_%s_dem.tif", basePath, tileName));
> iter = RandomIterFactory.create(image, null);
> cache.put(tileName, iter);
> }
> return iter;
> }
>
> // lat and lon in decimal degrees
> /*
> * (non-Javadoc)
> *
> * @see com.obteq.aster.reader.DemProvider#getElevation(double, double)
> */
> public double getElevation(double lat, double lon) throws Exception {
>
> lat -= .0001389;
> lon -= .0001389;
>
> // file name
> int latDegree = (int) Math.abs(lat);
> int lonDegree = (int) Math.abs(lon);
>
> char northSouth = (lat < 0) ? 'E' : 'N';
> char eastWest = (lon < 0) ? 'W' : 'E';
>
> String tileName = String.format("%c%2d%c%3d", northSouth,
> latDegree,
> eastWest, lonDegree).replace(" ", "0");
> // the frection only
> lat -= (int) lat;
> lon -= (int) lon;
>
> lat = Math.abs(lat);
> lon = Math.abs(lon);
>
> // calculate x and y of the image
> int y = 3600 - (int) (3600 * lat);
> int x = (int) (3600 * lon);
> // System.out.println(String.format("x=%d y=%d", x, y));
>
> // get the image from cache
>
> RandomIter iter = getTile(tileName);
> double av = iter.getSampleDouble(x, y, 0);
>
> return av;
> }
>
> public static void main(String args[]) throws Exception {
> DemProvider aster = new AsterDemReader("D:/OldHP");
> double elev = aster.getElevation(33.5, 42.5);
>
> System.out.println(elev);
> }
> }
>
> Could anyone please point me where I'm getting wrong? where can I find more
> info about reading ASTER DEM?
>
> Best Regards,
>
>
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