Mercator Map project problem, help needed!
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Programming Questions
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3 months ago
- /**
- * Utility class to convert between geo-locations and Cartesian screen coordinates.
- * Can be used with a bounding box defining the map section.
- *
- * (c) 2011 Till Nagel, tillnagel.com
- */
- public class MercatorMap {
- public static final float DEFAULT_TOP_LATITUDE = 80;
- public static final float DEFAULT_BOTTOM_LATITUDE = -80;
- public static final float DEFAULT_LEFT_LONGITUDE = -180;
- public static final float DEFAULT_RIGHT_LONGITUDE = 180;
- /** Horizontal dimension of this map, in pixels. */
- protected float mapScreenWidth;
- /** Vertical dimension of this map, in pixels. */
- protected float mapScreenHeight;
- /** Northern border of this map, in degrees. */
- protected float topLatitude;
- /** Southern border of this map, in degrees. */
- protected float bottomLatitude;
- /** Western border of this map, in degrees. */
- protected float leftLongitude;
- /** Eastern border of this map, in degrees. */
- protected float rightLongitude;
- private float topLatitudeRelative;
- private float bottomLatitudeRelative;
- private float leftLongitudeRadians;
- private float rightLongitudeRadians;
- public MercatorMap(float mapScreenWidth, float mapScreenHeight) {
- this(mapScreenWidth, mapScreenHeight, DEFAULT_TOP_LATITUDE, DEFAULT_BOTTOM_LATITUDE, DEFAULT_LEFT_LONGITUDE, DEFAULT_RIGHT_LONGITUDE);
- }
- /**
- * Creates a new MercatorMap with dimensions and bounding box to convert between geo-locations and screen coordinates.
- *
- * @param mapScreenWidth Horizontal dimension of this map, in pixels.
- * @param mapScreenHeight Vertical dimension of this map, in pixels.
- * @param topLatitude Northern border of this map, in degrees.
- * @param bottomLatitude Southern border of this map, in degrees.
- * @param leftLongitude Western border of this map, in degrees.
- * @param rightLongitude Eastern border of this map, in degrees.
- */
- public MercatorMap(float mapScreenWidth, float mapScreenHeight, float topLatitude, float bottomLatitude, float leftLongitude, float rightLongitude) {
- this.mapScreenWidth = mapScreenWidth;
- this.mapScreenHeight = mapScreenHeight;
- this.topLatitude = topLatitude;
- this.bottomLatitude = bottomLatitude;
- this.leftLongitude = leftLongitude;
- this.rightLongitude = rightLongitude;
- this.topLatitudeRelative = getScreenYRelative(topLatitude);
- this.bottomLatitudeRelative = getScreenYRelative(bottomLatitude);
- this.leftLongitudeRadians = getRadians(leftLongitude);
- this.rightLongitudeRadians = getRadians(rightLongitude);
- }
- /**
- * Projects the geo location to Cartesian coordinates, using the Mercator projection.
- *
- * @param geoLocation Geo location with (latitude, longitude) in degrees.
- * @returns The screen coordinates with (x, y).
- */
- public PVector getScreenLocation(PVector geoLocation) {
- float latitudeInDegrees = geoLocation.x;
- float longitudeInDegrees = geoLocation.y;
- return new PVector(getScreenX(longitudeInDegrees), getScreenY(latitudeInDegrees));
- }
- private float getScreenYRelative(float latitudeInDegrees) {
- return log(tan(latitudeInDegrees / 360f * PI + PI / 4));
- }
- protected float getScreenY(float latitudeInDegrees) {
- return mapScreenHeight * (getScreenYRelative(latitudeInDegrees) - topLatitudeRelative) / (bottomLatitudeRelative - topLatitudeRelative);
- }
- private float getRadians(float deg) {
- return deg * PI / 180;
- }
- protected float getScreenX(float longitudeInDegrees) {
- float longitudeInRadians = getRadians(longitudeInDegrees);
- return mapScreenWidth * (longitudeInRadians - leftLongitudeRadians) / (rightLongitudeRadians - leftLongitudeRadians);
- }
- }
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