Create Map Displays with Geographic Data

Example 1: Import Polygon Geographic Vector Data

Geographic vector data can be stored in a variety of different formats, for example shapefile and GPS Exchange (GPX) formats. This example imports polygon geographic vector data from a shapefile. Vertices in a shapefile can be either in geographic coordinates (latitude and longitude) or in a projected coordinate reference system.

Read USA state boundaries from the usastatehi.shp file included with the Mapping Toolbox™ software. The state boundaries are in latitude and longitude.

states = shaperead('usastatehi.shp','UseGeoCoords',true);

Example 2: Display Polygon Geographic Vector Data

Display the polygon geographic vector data onto an axesm-based map (previously referred to as map axes). Since the geographic extent is in the United States, you can use usamap to set up the map. Use geoshow to project and display the geographic data onto the map. Display an ocean color in the background by setting the frame's face color.

figure
ax = usamap('conus');
oceanColor = [0.3010 0.7450 0.9330];
landColor = [0.9290 0.6940 0.1250];
setm(ax,'FFaceColor',oceanColor)
geoshow(states,'FaceColor',landColor)
title({'Conterminous USA State Boundaries', ...
    'Polygon Geographic Vector Data'})

Example 3: Import Point and Line Geographic Vector Data

Import point geographic vector data from the boston_placenames.gpx file included with the Mapping Toolbox™ software. The file contains latitude and longitude coordinates of geographic point features in part of Boston, Massachusetts, USA. Use the readgeotable function to read the GPX file and return a geospatial table with one row for each point and its attributes.

places = readgeotable('boston_placenames.gpx');

Import line vector data from the sample_route.gpx file included with the Mapping Toolbox™ software. The file contains latitude and longitude coordinates for a GPS route from Boston Logan International Airport to The MathWorks, Inc in Natick Massachusetts, USA. Use the readgeotable function to read the GPX file and return a geospatial table contains each point along the route.

route = readgeotable('sample_route.gpx');

Example 4: Display Point and Line Geographic Vector Data

Display the geographic vector data in an axesm-based map centered around the state of Massachusetts, using the data from the state boundaries and the GPX files. The coordinates for all of these data sets are in latitude and longitude.

Find the state boundary for Massachusetts.

stateName = 'Massachusetts';
ma = states(strcmp({states.Name},stateName));

Use usamap to setup a map for the region surrounding Massachusetts. Color the ocean by setting the frame's face color. Display the state boundaries and highlight Massachusetts by using geoshow to display the geographic data onto the map. Since the GPX route is a set of points stored in a geopointshape vector, supply the latitude and longitude coordinates to geoshow to display the route as a line.

figure
ax = usamap('ma');
maColor = [0.4660 0.6740 0.1880];
setm(ax,'FFaceColor',oceanColor)
geoshow(states,'FaceColor',landColor)
geoshow(ma,'FaceColor',maColor)
geoshow(places);
geoshow(route.Shape.Latitude,route.Shape.Longitude);
title({'Massachusetts and Surrounding Region','Placenames and Route'})

Example 5: Set Latitude and Longitude Limits Based on Data Extent

Zoom into the map by computing new latitude and longitude limits for the map using the extent of the placenames and route data. Extend the limits by 0.05 degrees.

lat = [route.Shape.Latitude; places.Shape.Latitude];
lon = [route.Shape.Longitude; places.Shape.Longitude];
[latlim,lonlim] = geoquadpt(lat,lon);
[latlim,lonlim] = bufgeoquad(latlim,lonlim,0.05,0.05);

Construct an axesm-based map with the new limits and display the geographic data.

figure
ax = usamap(latlim,lonlim);
setm(ax,'FFaceColor',oceanColor)
geoshow(ma,'FaceColor',maColor)
geoshow(places)
geoshow(route.Shape.Latitude,route.Shape.Longitude)
title('Closeup of Placenames and Route')

Example 6: Import Geographic Raster Data

Geographic raster data can be stored in a variety of different formats, for example GeoTIFF, Esri Grid, DTED, and ENVI formats. To read data in these formats, use the readgeoraster function.

To read an image associated with a worldfile, use the imread and worldfileread functions instead. Use imread to read the image and worldfileread to read the worldfile and construct a spatial referencing object. For this example, import data for the region surrounding Boston, Massachusetts. The coordinates of the image are in latitude and longitude.

filename = 'boston_ovr.jpg';
RGB = imread(filename);
R = worldfileread(getworldfilename(filename),'geographic',size(RGB));

Example 7: Display Geographic Raster Data

Display the RGB image onto an axesm-based map. The limits of the map are set to the limits defined by the spatial referencing object, R. The coordinates of the data are in latitude and longitude.

figure
ax = usamap(RGB,R);
setm(ax,'MLabelLocation',0.05,'PLabelLocation',0.05, ...
    'MLabelRound',-2,'PLabelRound',-2)
geoshow(RGB,R)
title('Boston Overview')

Example 8: Display Geographic Vector and Raster Data

You can display raster and vector data in a single map display. Since the coordinates for all of these data sets are in latitude and longitude, use geoshow to display them in a single map display. Setup new limits based on the limits of the route, placenames, and the overview image.

lat = [route.Shape.Latitude'  places.Shape.Latitude'  R.LatitudeLimits];
lon = [route.Shape.Longitude' places.Shape.Longitude' R.LongitudeLimits];
[latlim,lonlim] = geoquadpt(lat,lon);

figure
ax = usamap(latlim,lonlim);
setm(ax,'GColor','k','PLabelLocation',0.05,'PLineLocation',0.05)
geoshow(RGB,R)
geoshow(ma.Lat,ma.Lon,'LineWidth',2,'Color','y')
geoshow(places)
geoshow(route.Shape.Latitude,route.Shape.Longitude)
title('Boston Overview and Geographic Vector Data')

Example 9: Customize a Map Display with a Scale Ruler

Customize a map display by including a scale ruler. A scale ruler is a graphic object that shows distances on the ground at the correct size for the projection. This example illustrates how to construct a scale ruler that displays horizontal distances in international miles.

Compute latitude and longitude limits of Massachusetts and extend the limits by 0.05 degrees by using the bufgeoquad function.

[latlim,lonlim] = geoquadline(ma.Lat,ma.Lon);
[latlim,lonlim] = bufgeoquad(latlim,lonlim,0.05,0.05);

Display the state boundary, placenames, route, and overview image onto the map.

figure
ax = usamap(latlim,lonlim);
setm(ax,'FFaceColor',oceanColor)
geoshow(states,'FaceColor',landColor)
geoshow(ma,'LineWidth',1.5,'FaceColor',maColor)
geoshow(RGB,R)
geoshow(places)
geoshow(route.Shape.Latitude,route.Shape.Longitude)
titleText = 'Massachusetts and Surrounding Region';
title(titleText)

Insert a scale ruler. You can determine a location for the scale ruler by using the ginput function as shown below:

[xLoc,yLoc] = ginput(1);

A location previously chosen is set below.

xLoc = -127800;
yLoc = 5014700;
scaleruler('Units','mi','RulerStyle','patches',  ...
    'XLoc',xLoc,'YLoc',yLoc);
title({titleText,'with Scale Ruler'})

Example 10: Customize a Map Display with a North Arrow

Customize the map by adding a north arrow. A north arrow is a graphic element pointing to the geographic North Pole.

Use latitude and longitude values to position the north arrow.

northArrowLat =  42.5;
northArrowLon = -70.25;
northarrow('Latitude',northArrowLat,'Longitude',northArrowLon);
title({titleText,'with Scale Ruler and North Arrow'})

Example 11: Customize a Map Display with an Inset Map

Customize the map by adding an inset map. An inset map is a small map within a larger map that enables you to visualize the larger geographic region of your main map. Create a map for the surrounding region as an inset map. Use the axes function to contain and position the inset map. In the inset map:

h2 = axes('Position',[0.15 0.6 0.2 0.2],'Visible','off');
usamap({'PA','ME'})
plabel off
mlabel off
setm(h2,'FFaceColor','w')
geoshow(states,'FaceColor',[0.9 0.9 0.9],'Parent',h2)
plotm(latlim([1 2 2 1 1]),lonlim([2 2 1 1 2]), ...
    'Color','red','LineWidth',2)
title(ax,{titleText,'with Scale Ruler, North Arrow, and Inset Map'})

Data Set Information

The file boston_placenames.gpx is from the Bureau of Geographic Information (MassGIS), Commonwealth of Massachusetts, Executive Office of Technology and Security Services. For more information about the data sets, use the command type boston_placenames_gpx.txt.

The file boston_ovr.jpg includes materials copyrighted by GeoEye, all rights reserved. GeoEye was merged into the DigitalGlobe corporation on January 29th, 2013. For more information about the data set, use the command type boston_ovr.txt.