* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+/**
+ * SECTION:gis-util
+ * @short_description: Geographic utilities
+ *
+ * Miscellaneous utility functions, these deal mostly with coordinate
+ * conversion. Below are some examples that should help demonstrate how these
+ * functions work.
+ *
+ * <example>
+ * <title>Terminology</title>
+ * <programlisting>
+ * deg - Degrees
+ * rad - Radians, also radius
+ * m - Meters, for earth-based distances
+ * px - Pixels, for screen-based distances
+ *
+ * height - Height, the distance above the geoid (ground)
+ * elev - Elevation, the distance above the spheroid
+ * rad - Radius, the distance from the center of the earth
+ *
+ * lat - Latitude, amount north-south, -90 (S) .. 90 (N)
+ * lon - Longitude, amount east-west, -180 (W) .. 180 (E)
+ * incl - Inclination, polar equiv of latitude, Pi .. 0
+ * azim - Azimuth, polar equiv of longitude, -Pi .. Pi
+ *
+ * x - 0° lon is positive
+ * y - 90° lon is positive
+ * z - North pole is positive
+ *
+ * llh - lat,lon,height
+ * lle - lat,lon,elev
+ * llr - lat,lon,rad
+ * pol - incl,azim,rad
+ * xyz - x,y,z
+ * </programlisting>
+ * </example>
+ *
+ * <example>
+ * <title>Conversions</title>
+ * <programlisting>
+ * lat lon elev -> x y z
+ * lle2xyz: 0.0, 0.0, 0.0 -> 0.0, 0.0, 10.0
+ * lle2xyz: 90.0, 0.0, 0.0 -> 0.0, 10.0, 0.0
+ * lle2xyz: 0.0, 90.0, 0.0 -> 10.0, 0.0, 0.0
+ *
+ * x y z -> lat lon elev
+ * xyz2lle: 10.0, 0.0, 0.0 -> 0.0, 90.0, 0.0
+ * xyz2lle: 0.0, 10.0, 0.0 -> 90.0, 0.0, 0.0
+ * xyz2lle: 0.0, 0.0, 10.0 -> 0.0, 0.0, 0.0
+ * </programlisting>
+ * </example>
+ */
+
#include <glib.h>
#include <math.h>
/******************
* Global helpers *
******************/
+/**
+ * lle2xyz:
+ * @lat: the latitude
+ * @lon: the longitude
+ * @elev: the elevation
+ * @x: the resulting x coordinate
+ * @y: the resulting y coordinate
+ * @z: the resulting z coordinate
+ *
+ * Convert a point from latitude, longitude, and elevation to x, y and z
+ * coordinates.
+ */
void lle2xyz(gdouble lat, gdouble lon, gdouble elev,
gdouble *x, gdouble *y, gdouble *z)
{
*y = rad * cos(incl);
}
+/**
+ * xyz2lle:
+ * @x: the x coordinate
+ * @y: the y coordinate
+ * @z: the z coordinate
+ * @lat: the resulting latitude
+ * @lon: the resulting longitude
+ * @elev: the resulting elevation
+ *
+ * Convert a point from x, y and z coordinates to latitude, longitude, and
+ * elevation.
+ */
void xyz2lle(gdouble x, gdouble y, gdouble z,
gdouble *lat, gdouble *lon, gdouble *elev)
{
*elev = rad2elev(rad);
}
+/**
+ * xyz2ll:
+ * @x: the x coordinate
+ * @y: the y coordinate
+ * @z: the z coordinate
+ * @lat: the resulting latitude
+ * @lon: the resulting longitude
+ *
+ * Get the latitude and longitude for a x, y, z value.
+ */
void xyz2ll(gdouble x, gdouble y, gdouble z,
gdouble *lat, gdouble *lon)
{
*lon = azim2lon(atan2(x,z));
}
+/**
+ * ll2m:
+ * @lon_dist: the distance in degrees of longitude
+ * @lat: the latitude to calculate at
+ *
+ * Calculate the distance of longitudinal span at a particular latitude.
+ *
+ * Returns: the distance in meters
+ */
gdouble ll2m(gdouble lon_dist, gdouble lat)
{
gdouble azim = (-lat+90)/180*M_PI;
return lon_dist/360 * circ;
}
+/**
+ * distd:
+ * @a: the first point
+ * @b: the second point
+ *
+ * Calculate the distance between two three dimensional points.
+ *
+ * Returns: the distance between the points
+ */
gdouble distd(gdouble *a, gdouble *b)
{
return sqrt((a[0]-b[0])*(a[0]-b[0]) +
(a[2]-b[2])*(a[2]-b[2]));
}
+/**
+ * lon_avg:
+ * @a: the first longitude
+ * @b: the second longitude
+ *
+ * Calculate the average longitude between two longitudes. This is smart about
+ * which side of the globe the resulting longitude is placed on.
+ *
+ * Returns: the average
+ */
gdouble lon_avg(gdouble a, gdouble b)
{
gdouble diff = ABS(a-b);
#include <glib.h>
+/**
+ * EARTH_R:
+ *
+ * Radius of the earth
+ */
#define EARTH_R (6371000)
+
+/**
+ * EARTH_C:
+ *
+ * Circumference of the earth at the equator
+ */
#define EARTH_C (2*G_PI*EARTH_R)
+
+/**
+ * NORTH:
+ *
+ * Latitude at the north poll
+ */
#define NORTH 90
+
+/**
+ * SOUTH:
+ *
+ * Latitude at the south poll
+ */
#define SOUTH -90
+
+/**
+ * EAST:
+ *
+ * Eastern most longitude
+ */
#define EAST 180
+
+/**
+ * WEST:
+ *
+ * Western most longitude
+ */
#define WEST -180
+/***************
+ * Conversions *
+ ***************/
/**
- * Terms
- * -----
- * deg - Degrees
- * rad - Radians, also radius
- * m - Meters, for earth-based distances
- * px - Pixels, for screen-based distances
+ * azim2lon:
+ * @azim: the azimuth in radians
*
- * height - Height, the distance above the geoid (ground)
- * elev - Elevation, the distance above the spheroid
- * rad - Radius, the distance from the center of the earth
+ * Convert azimuth to longitude
*
- * lat - Latitude, amount north-south, -90 (S) .. 90 (N)
- * lon - Longitude, amount east-west, -180 (W) .. 180 (E)
- * incl - Inclination, polar equiv of latitude, Pi .. 0
- * azim - Azimuth, polar equiv of longitude, -Pi .. Pi
+ * Returns: the longitude
+ */
+#define azim2lon(azim) ((azim)*180/G_PI)
+
+/**
+ * lon2azim:
+ * @lon: the longitude
*
- * x - 0° lon is positive
- * y - 90° lon is positive
- * z - North pole is positive
+ * Convert longitude to azimuth
*
- * llh - lat,lon,height
- * lle - lat,lon,elev
- * llr - lat,lon,rad
- * pol - incl,azim,rad
- * xyz - x,y,z
+ * Returns: the azimuth in radians
*/
+#define lon2azim(lon) ((lon)*G_PI/180)
/**
- * lat lon elev -> x y z
- * lle2xyz: 0.0, 0.0, 0.0 -> 0.0, 0.0, 10.0
- * lle2xyz: 90.0, 0.0, 0.0 -> 0.0, 10.0, 0.0
- * lle2xyz: 0.0, 90.0, 0.0 -> 10.0, 0.0, 0.0
+ * incl2lat:
+ * @incl: the inclination in radians
*
- * x y z -> lat lon elev
- * xyz2lle: 10.0, 0.0, 0.0 -> 0.0, 90.0, 0.0
- * xyz2lle: 0.0, 10.0, 0.0 -> 90.0, 0.0, 0.0
- * xyz2lle: 0.0, 0.0, 10.0 -> 0.0, 0.0, 0.0
+ * Convert inclination to latitude
+ *
+ * Returns: the latitude
*/
-
#define incl2lat(incl) (90-(incl)*180/G_PI)
+
+/**
+ * lat2incl:
+ * @lat: the latitude
+ *
+ * Convert latitude to inclination
+ *
+ * Returns: the inclination in radians
+ */
#define lat2incl(lat) ((90-(lat))*G_PI/180)
+
+/**
+ * rad2elev:
+ * @rad: the radius in meters
+ *
+ * Convert radius to elevation
+ *
+ * Returns: the elevation in meters above the earth surface
+ */
#define rad2elev(rad) ((rad)-EARTH_R)
+
+/**
+ * elev2rad:
+ * @elev: the elevation in meters above the earth surface
+ *
+ * Convert elevation to radius
+ *
+ * Returns: the radius in meters
+ */
#define elev2rad(elev) ((elev)+EARTH_R)
+/**
+ * deg2rad:
+ * @deg: the angle in degrees
+ *
+ * Convert degrees to radians
+ *
+ * Returns: the angle in radians
+ */
#define deg2rad(deg) (((deg)*G_PI)/180.0)
+
+/**
+ * rad2deg:
+ * @rad: the angle in radians
+ *
+ * Convert radians to degrees
+ *
+ * Returns: the angle in degrees
+ */
#define rad2deg(rad) (((rad)*180.0)/G_PI)
+
+/********
+ * Misc *
+ ********/
+/**
+ * FOV_DIST:
+ *
+ * Used by GisOpenGL to set up the drawing window
+ */
#define FOV_DIST 2000.0
+
+/**
+ * MPPX:
+ * @dist: the distance between the eye and the point in question
+ *
+ * Get the resolution that a point would be drawn at on the screen
+ *
+ * Returns: the resolution in meters per pixel
+ */
#define MPPX(dist) (4*dist/FOV_DIST)
void lle2xyz(gdouble lat, gdouble lon, gdouble elev,