User`s guide

21-3
Changes to Atlas Data and Associated Functions
Through Version 2.0.3, the toolbox included a set of atlas data with global geopolitical
data embedded as MATLAB arrays in four MAT-files: worldlo, worldhi, worldmtx,
and worldmtxmed. However, geopolitical data is difficult to keep current, and is subject
to inaccuracies and interpretations that can cause contention. Therefore, starting with
Version 2.1, Mapping Toolbox demo data now excludes geopolitical data that would
specify national sovereignty over specific regions of the Earth. The only exceptions are
the boundaries of the 50 U.S. states and the District of Columbia.
Compatibility Considerations
This change means that the worldlo, worldhi, worldmtx, and worldmtxmed MAT-
files are no longer part of the toolbox. However, the nonpolitical data on global coastlines,
major lakes and inland seas, major rivers, and major cities and populated places that was
in worldlo.mat has been retained in the toolbox and transformed into shapefile format.
This includes the addition of name attributes for many previously unnamed features.
There are four new shapefiles in this category: landareas.shp, worldlakes.shp,
worldrivers.shp, and worldcities.shp.
For consistency, the atlas data for the United States that was originally stored in
the usalo and usahi MAT-files has also been transformed, although none has
been removed. These data sets now reside in the following shapefiles and MAT-files:
usastatelo.shp, usastatehi.shp, conus.mat, and greatlakes.mat.
The toolbox originally included four functions dedicated to extracting data from the
atlas data MAT-files: worldlo, worldhi, usalo, and usahi. With the data removal/
transformation described above, these functions are no longer needed and have been
removed from the toolbox in Version 2.1. You can easily access the new shapefiles
using the shaperead function, which includes powerful and flexible options for
selecting features and even controlling which attributes are read. In addition, function
country2mtx, whose sole purpose was to rasterize the country boundary polygons in
worldlo.mat, has been removed.
Related changes extend to the worldmap function, which formerly combined two
purposes:
• Select an appropriate map projection and parameters with which to display a given
latitude-longitude area.
• Automatically display atlas data for that area.