The Map Frame
The Mapping Toolbox™
map frame is the outline of the limits of a map, often in the
form of a box, the "edge of the world," so to speak. The frame is
displayed if the map axes property Frame is set to
'on'. This can be accomplished upon map axes creation with
axesm, or later with setm, or with the direct
command framem on. The frame is geographically defined as a
latitude-longitude quadrangle that is projected appropriately. For example, on a map of
the world, the frame might extend from pole to pole and a full 360° range of longitude.
In appearance, the frame would take on the characteristic shape of the projection. The
examples below are full-world frames shown in four very different projections.
Full-World Map Frames
As a map object, each of the previously displayed frames is identical; however, the selection of a display projection has varied their appearance.
You can manipulate properties beyond the latitude and longitude limits of the frame.
Frame properties are established upon map axes object creation; you can modify them
subsequently with the setm and the framem
functions. The command framem alone is a toggle for the
Frame property, which controls the visibility of the frame. You
can also call framem with property names and values to alter the
appearance of the frame:
framem('FlineWidth',4,'FEdgeColor','red')
The frame is actually a patch with a default face color set to
'none' and a default edge color of black. You can alter these map
axes properties by manipulating the FFaceColor and
FEdgeColor properties. For example, the command
setm(gca,'FFaceColor','cyan')
makes the background region of your display resemble water. Since the frame patch is
always the lowest layer of a map display, other patches, perhaps representing land, will
appear above the "water." If an object is subsequently plotted "below" the frame patch,
the frame altitude can be recalculated to lie below this object with the command
framem reset. The frame is replaced and not reprojected.
Set the line width of the edge, which is 2 points by default, using the
FLineWidth property.
The primary advantage of displaying the map frame is that it can provide positional context for other displayed map objects. For example, when vector data of the coasts is displayed, the frame provides the "edge" of the world.
See the framem reference page for more
details.