Class Mapx

Create an empty Mapx object.

None.

An empty, uninitialized Mapx object.

var mx = new Mapx;

After creating the object, you must initialize it by calling the setupvars method below.

Sets up the Mapx object parameters

projection_name - A string of the projection name
lat0 - lat0 value used by the projection (*)
lon0 - lon0 value used by the projection (*)
lat1 - lat1 value used by the projection (*)
lon1 - lon1 value used by the projection (*)
rotation - The rotation angle to use
scale - The scale factor to use
center_lat - The latitude of the projection center (*)
center_lon - The longitude of the projection center (*)
south - The southernmost limit of the projection
north - The northernmost limit of the projection
west - The westernmost limit of the projection
east - The easternmost limit of the projection
lat_interval - The latitude interval (**)
lon_interval - The longitude interval (**)
label_lat - The label for latitude (**)
label_lon - The label for longitude (**)
cil_detail - 1 or 0, represents Coastline/Island/Lake (**)
bdy_detail - 1 or 0, represents political boundaries (**)
riv_detail - 1 or 0, represents rivers (**)
equatorial_radius - Optional radius of the equator
eccentricity - Optional eccentricity for ellipse projections

None.

mx.setupvars('Azimuthal Equal-Area', 90, 0, 0, 0,
0, 1, 90, 0, 0, 90, -180, 180, 15, 30, 0, 0,
0, 0, 1, 6371228.0, 0);
// Creates a Mapx object using the Azimuthal Equal-Area projection
// and the parameters given above.

The values marked with (**) are not currently utilized by this version of Mapx, but represent values that may be useful in future applications. They are used for display purposes, not calculation purposes. It is possible in future versions that these values may be removed, though if this happens tis version will still be available for backwards compatibility. equatorial_radius is optional. If it is not provided, a default value of 6371.228 is used. eccentricity is optional, and only used for projections that use an elliptical earth. If so, and the value is not provided, a default value of 0.082271673 is used. The projection name is not used except for display purposes, though it is advised that it represent the name of the proejction object being used for the class. The parameters marked as (*) above are specific to the projections. Some projections may not use certain values, in which case any value can be used as a place- holder for those values. The south boundary cannot be greater than the north boundary. However, the west boundary may be greater than the east boundary. If so, this will mean the map boundaries straddle the dateline.

Reinitializes internal variables based on the parameters.

None.

False if there was a problem with the initialization, true otherwise

var status = mx.reinit_mapx();
// Reinitializes internal Mapx variables and returns the status
// of whether it was successful

This should always be called after using the setupvars method, to ensure that other internal variables are set correctly.

Determines if a lat/lon coordinate is within the set Mapx bounds.

lat - The latitude value of the coordinate
lon - The longitude value of the coordinate

True if the coordinate is within the bounds, false otherwise.

var inbounds = mx.within_mapx(30.3, -30.2);
// Returns true if the coordinate 30.3N, -30.2S is within the
// boundaries set for the projection

Latitude values can be any numeric value. This value will be normalized into a -180 to 180 range before checking validity. Negative lat/lon values represent South/West, positive represent North/East.

Converts a lat/lon coordinate to an x/y map coordinate.

lat - The latitude value to convert
lon - The longitude value to convert
u - An array to hold the "x" result
v - An array to hold the "y" result

False if there is an error converting, true otherwise.

var status = mx.forward_mapx(30.3, -40.2, x, y);
// Converts the coordinate 30.3N, 40.2W to the x/y values
// that coordinate represents on the projected map.

u and v are used for parameters to account for potential rotation of the projection. This method really wraps the projection- specific geo_to_map method. The u and v arrays must be pre- allocated. The results will be stored in u[0] and v[0].

Converts an x/y map coordiate to a lat/lon coordinate

u - The "x" value to convert
v - The "y" value to convert
lat - An array to hold the latitude value
lon - An array to hold the longitude value

False if there is an error converting, true otherwise.

var status = mx.inverse_mapx(300, 400, lat, lon);
// Converts the coordinate 300,400 into the respective
// latitude/longitude value.

u and v are used for parameters to account for potential rotation of the projection. This method really wraps the projection- specific map_to_geo method. The lat and lon arrays must be pre- allocated. The results will be stored in u[0] and v[0]

Sets up projection-specific initialization

None.

False if there is an error initializing, true otherwise.

var status = mx.initialize();
// Initializes projection variables

THIS METHOD MUST BE OVERWRITTEN IN ALL INHERITED CLASSES. This method should be called after setupvars to initialize any projection-specific information, such as defining constants used or making complex calculations based on the preset parameters. If you call reinit_mapx, this will be called for you. The overwritten method must return a boolean value, true to represent success, false to represent failure.

Converts from lat/lon to x/y

lat - The latitude value to convert
lon - The longitude value to convert
u - An array to hold the "x" result
v - An array to hold the "y" result

False if there is an error converting, true otherwise.

var status = mx.forward_mapx(30.3, -40.2, x, y);
// Converts the coordinate 30.3N, 40.2W to the x/y values
// that coordinate represents on the projected map.

THIS METHOD MUST BE OVERWRITTEN IN ALL INHERITED CLASSES. This method is where the actual work of converting from a lat/lon value to an x/y value should go. The following should be done for the implementation of this method: - Results should be stored in u[0] and v[0]. These results should account for rotation, if applicable. - The method should return true if the conversion is successful, false if not.

Converts an x/y map coordiate to a lat/lon coordinate

u - The "x" value to convert
v - The "y" value to convert
lat - An array to hold the latitude value
lon - An array to hold the longitude value

False if there is an error converting, true otherwise.

var status = mx.inverse_mapx(300, 400, lat, lon);
// Converts the coordinate 300,400 into the respective
// latitude/longitude value.

THIS METHOD MUST BE OVERWRITTEN IN ALL INHERITED CLASSES. This method is where the actual work of converting from an x/y value to a lat/lon value should go. The following should be done for the implementation of this method: - Results should be stored in lat[0] and lon[0]. These results should account for rotation, if applicable. - The method should return true if the conversion is successful, false if not.