Trim lines to latitude-longitude quadrangle
[lat,lon] = maptriml(lat0,lon0,latlim,lonlim)
[lat,lon] = maptriml(lat0,lon0,latlim,lonlim) returns filtered
vector map data sets from which all points lying outside the desired
latitude and longitude limits have been discarded. These limits are
specified by the two-element vectors
which have the form
[south-limit north-limit] and
Trim Lines to Region of Interest
It is not unusual for vector data to extend beyond the geographic region currently of interest. For example, you might have coastline data for the entire world, but are interested in mapping Australia only. In this and other situations, you might want to eliminate unnecessary data from the workspace and from calculations in order to save memory or to speed up processing and display. You can trim line data by simply removing points outside the region of interest by clipping lines at the map frame or to some other defined region. The
maptriml function returns variables containing only those points that lie within the defined region.
coastlines MAT-file. This file contains data for the entire world.
Define a region of interest centered on Australia.
latlim = [-50 0]; lonlim = [105 160];
Delete all line data outside these limits, producing line vectors, by using the
[linelat,linelon] = maptriml(coastlat,coastlon,latlim,lonlim);
Examine the variables to see how much data has been reduced. The clipped data is only 10% as large as the original data set.
Name Size Bytes Class Attributes coastlat 9865x1 78920 double coastlon 9865x1 78920 double latlim 1x2 16 double linelat 977x1 7816 double linelon 977x1 7816 double lonlim 1x2 16 double
Plot the trimmed line data using a Miller projection.
axesm('MapProjection', 'miller', 'Frame', 'on',... 'FlatLimit', latlim, 'FlonLimit', lonlim) geoshow(linelat,linelon)