Create 3-D Displays with Raster Data

This example shows how to create 3-D displays with raster data by setting up surface views, which requires explicit horizontal coordinates. The simplest way to display raster data is to assign colors to matrix elements according to their data values and view them in two dimensions. Raster data maps also can be displayed as 3-D surfaces using the matrix values as the z data. The difference between regular raster data and a geolocated data grid is that each grid intersection for a geolocated grid is explicitly defined with x-y or latitude/longitude matrices or is interpolated from a graticule, while a regular matrix only implies these locations (which is why it needs a reference vector, matrix, or object).

Load elevation data and a geographic cells reference object for the Korean peninsula. Transform the data and reference object to a fully geolocated data grid using the meshgrat function.

load korea5c
[lat,lon] = meshgrat(korea5c,korea5cR);

Next use the km2deg function to convert the units of elevation from meters to degrees, so they are commensurate with the latitude and longitude coordinate matrices.

korea5c = km2deg(korea5c/1000);

Observe the results by typing the whos command. The lat and lon coordinate matrices form a mesh the same size as korea5c. This is a requirement for constructing 3-D surfaces. In lon, all columns contain the same number for a given row, and in lat, all rows contain the same number for a given column. This is because the mesh produced by meshgrat in this case is regular, but such data grids need not have equal spacing.

whos

  Name               Size              Bytes  Class                                     Attributes

  description        2x64                256  char                                                
  korea5c          180x240            345600  double                                              
  korea5cR           1x1                 128  map.rasterref.GeographicCellsReference              
  lat              180x240            345600  double                                              
  lon              180x240            345600  double                                              
  source             2x76                304  char                                                

Now set up a map axes object with the equal area conic projection and, instead of using the meshm function to make this map, display the geolocated data grid using the surfm function. Set an appropriate colormap. This produces a map that is really a 3-D view seen from directly overhead (the default perspective). To appreciate that, all you need to do is to change your viewpoint.

axesm('MapProjection','eqaconic','MapParallels',[],...
     'MapLatLimit',[30 45],'MapLonLimit',[115 135])
surfm(lat,lon,korea5c,korea5c)
demcmap(korea5c)
tightmap

Specify a viewing azimuth of 60 degrees (from the east southeast) and a viewing elevation of 30 degrees above the horizon, using the view function.

view(60,30)