MAP_LAND Procedure

For each map pixel, identify longitude, latitude, and cover type.

Usage

p = MAP_LAND(r)

Input Parameters

r—The range used in the call to MAP, /exact: MAP,range=r,/exact.

Returned Value

p—An (n,3) array specifying longitude, latitude, and surface cover type (0 = liquid, 1 = solid) for each pixel of the map currently displayed in an X or WIN32 window.

Keywords

Fast—If set, the algorithm computes surface cover type by direct interpolation of 1/20th degree resolution data supplied by the department of geography at Boston University (in turn derived from NASA data). For map ranges greater 60 degrees, this data is often sufficiently accurate. By default, fast is not set and the interpolated surface cover data is manipulated so that it follows coastline data of higher resolution;

Wide—The number of pixels that the algorithm uses to describe the width of a coastline. The default of 2 should usually be sufficient, but other values may occasionally give better results.

Ulim—Non-negative integer parameter used by the algorithm. The default is 4, but values from 2 to 8 may sometimes give better results.

Example

WINDOW, Xsize=600, Ysize=600
MAP, Range=[-76, -56, -64, -48], /Exact, Projection=9, Boundary=2
p = MAP_LAND([-76, -56, -64, -48])
a = WHERE(p(*, 2))
MAP_PLOTS, p(a, 0), p(a, 1), Psym=3

See Also

MAP, MAP_PLOTS