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What does a Mapping toolbox do?
Imagine that you are given the task of displaying the population of countries. Wouldn’t it be more attractive when this data is displayed in a map, rather than a table? This is precisely what the mapping toolbox helps us with. Before seeing about how to create maps and globes, let us see what a Mapping toolbox does and what its uses are. Mapping Toolbox provides algorithms, functions, and app for analysing geographic data and creating map displays in MATLAB. You can import vector and raster data from a wide range of file formats and web map servers. Geospatial data can be combined with base map layers from multiple sources in a single map display.
Primary functions of the toolbox
In this blog, we shall see a few essential functions of this toolbox. The main topic that we will be concentrating in this blog would be performing various 2D and 3D maps and globe displays. We are going to see the following implementations in MATLAB:
- Creating Maps Using MAPSHOW
- Display a Rotating Globe
- Creating an Interactive globe
- Visualizing the COVID-19 cases in a map
1) Creating Maps Using MAPSHOW
As a beginner and very first step, we shall see how we can create different varieties of road maps using the mapshow function in a simple code. As the first step in every code, we would use the clc, clear, and close commands to clear all the variables and close all the opened images.
clc
clear
close all
Map 1: Roads - A Geographic Data Structure
Map 2: Roads with Custom LineStyle
Map 3: Roads with SymbolSpec
Map 4: GeoTIFF Image of Boston
2) Display a Rotating Globe
As a second application of the mapping toolbox, we shall see how to animate to produce a rotating globe.
clc
clear
close all
Now we shall set up a Globe display. The view is from above the North Pole.
figure
axesm('globe');
gridm('GLineStyle','-','Gcolor',[.7 .8 .9],'Grid','on')
In the above figure, the globe appears similar to how it will look when we see it from above the north pole. It looks like a 2-D circle, rather than a 3-D sphere.
Next, we shall spin the globe by one revolution.
set(gca,'Box','off','Projection','perspective')
spin
For this, we have used the spin.m function in MATLAB.
% spin.m: Rotates a view around the equator one revolution
% in 5-degree steps. Negative step makes it rotate normally
% (west-to-east).
for i=90:-5:-270
view(i,23.5); % Earth's axis tilts by 23.5 degrees
drawnow
end
We have the skeletal structure of the 3-D globe in the above image.Add the base color of copper color to give a feeling of land and spin at a slower rate.
base = zeros(180,360);
baseR = georefcells([-90 90],[0 360],size(base));
copperColor = [0.62 0.38 0.24];
hs = geoshow(base,baseR,'FaceColor',copperColor);
setm(gca,'Galtitude',0.025);
axis vis3d
spin
Show the Earth in space. Blacken the figure background, turn off the three axes, and spin again.
clmo(hs)
load topo
topo = topo / (earthRadius('km')* 20);
hs = meshm(topo,topolegend,size(topo),topo);
demcmap(topo)
set(gcf,'color','black');
axis off;
spin
The above figure shows the globe with its geographic colors of green and blue.
Applying lighting, which shifts as the planet rotates and makes it brighter.
camlight right
lighting Gouraud;
material ([.7, .9, .8])
The above picture shows a brighter globe and also with more clear terrains.
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3) Creating an Interactive globe
In the third application topic, we will see how we can construct a map of major world cities enhanced with coastlines and terrain. We shall also see how to interactively pick a location and get the name and location of the nearest city.
clc
clear
close all
Set up a Map Axes Object and Render a Global Elevation Grid. Construct the axes.
figure
axesm bries
text(.8, -1.8, 'Briesemeister projection')
framem('FLineWidth',1)
Load and display a 1-by-1-degree elevation grid.
load topo
geoshow(topo, topolegend, 'DisplayType', 'texturemap')
%Improve the Terrain Display. Get a colormap appropriate for elevation.
demcmap(topo)
%Make it brighter
brighten(.5)
%Add Simplified Coastlines. Load global coastline coordinates
load coastlines
%Generalize the coastlines to 0.25-degree tolerance
[rlat, rlon] = reducem(coastlat,coastlon, 0.25);
%Plot the coastlines in brown.
geoshow(rlat, rlon, 'Color', [.6 .5 .2], 'LineWidth', 1.5)
Plot City Locations with Red Point Markers
Select Cities Interactively
As the output of this code, we can see how the map will be projected in a Briesemeister projection. Also, here I have placed the cursor near Delhi, and we can see the output name mentioned as New Delhi along with its latitude and longitude coordinates displayed as 28.63 and 77.21.
4) Visualizing the COVID-19 cases in a map
The entire world is now in a hazardous situation as we see the number of COVID-19 cases rising in huge numbers daily. As a final application of this blog, I felt it would be relevant if we can plot and visualize the Covid-19 cases in a map using the mapping toolbox.
Geobubble mapping
Geobubble mapping format will be used for the visualizing purpose, where the cases will be shown in the form of a bubble in each country. The size and color of the bubble would indicate the severity of the disease. Highly affected countries would have a more giant bubble in the map compared to a country with a low number of cases. This is the geobubble mapping format.
clc
clear
close all
Getting data of the countries
Visualization of Geo Bubble mapping
Conclusion
In this blog, we came across a few essential functions and implementations of the mapping toolbox. We also saw one application of it relevant to today’s situation. The mapping toolbox can also be extended to various other applications such as Web mapping, Terrain and elevation analysis, Geometric Geodesy and map projections, Data representation and transformations, etc.
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