77 lines
1.7 KiB
Java
77 lines
1.7 KiB
Java
package net.osmand;
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import java.io.EOFException;
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import java.io.File;
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import java.io.FileNotFoundException;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import org.apache.commons.logging.Log;
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public class GeoidAltitudeCorrection {
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private final Log log = PlatformUtil.getLog(GeoidAltitudeCorrection.class);
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private File f;
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private RandomAccessFile rf;
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private int cachedPointer = -1;
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private short cachedValue = 0;
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public GeoidAltitudeCorrection(File dir) {
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String[] fnames = dir.list();
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if(fnames != null) {
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String fn = null;
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for(String f : fnames) {
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if(f.contains("WW15MGH")) {
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fn = f;
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break;
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}
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}
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if (fn != null) {
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this.f = new File(dir, fn);
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if (f.exists()) {
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try {
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rf = new RandomAccessFile(f.getPath(), "r");
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} catch (FileNotFoundException e) {
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log.error("Error", e);
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}
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}
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}
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}
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}
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public boolean isGeoidInformationAvailable(){
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return rf != null;
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}
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public float getGeoidHeight(double lat, double lon) {
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if (!isGeoidInformationAvailable()) {
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return 0;
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}
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int shy = (int) Math.floor((90 - lat) * 4);
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int shx = (int) Math.floor((lon >= 0 ? lon : lon + 360) * 4);
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int pointer = ((shy * 1440) + shx) * 2;
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short res = 0;
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if (pointer != cachedPointer) {
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try {
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rf.seek(pointer);
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// read short
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cachedValue = readShort();
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cachedPointer = pointer;
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} catch (IOException e) {
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log.error("Geoid info error", e);
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}
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}
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res = cachedValue;
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return res / 100f;
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}
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private short readShort() throws IOException {
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byte[] b = new byte[2];
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rf.read(b);
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int ch1 = b[0] < 0 ? b[0] + 256 : b[0];
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int ch2 = b[1] < 0 ? b[1] + 256 : b[1];
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return (short)((ch1 << 8) + ch2);
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}
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}
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