[Geotools-gt2-users] Reading ASTER DEM Data

[Ahmad Al-Obaidy]

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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