MATLAB: Get data from basemap ‘topographic’

basemap

Hi i have two question:

1) I want to use the matlab basemap 'topographic' and plot on it a rectangle how can i do this?

2) how can i know the elevation of a point on the basemap if i know the longitude and latitude of the point?

THANKS

Best Answer

1. In order to plot a rectangle on the matlab basemap ‘topographic’, use the below code.

xRec = [44.56 44.51 44.51 44.56 44.56];
yRec = [-72.73 -72.73 -72.63 -72.63 -72.73];
geoplot(xRec, yRec,'r','LineWidth',5);
geobasemap('landcover')                   %  Here, ‘landcover’ is the basemap

For more information, refer the following link:

https://www.mathworks.com/help/map/ref/addcustombasemap.html

2. To know the elevation of a point on the basemap, you can refer to "getElevations” which is one of the several submissions in MATLAB File Exchange on MATLAB Central which is a forum for our product users to interact, exchange information and knowledge, without MathWorks' involvement.

Feel free to contact the author of this submission directly for specific questions about the implementation.

Related Solutions

MATLAB: How to plot a map and calculate distance between two points in the Geographic Space

Showing the map in a figure There are different projections as shown in documentation page in https://www.mathworks.com/help/map/summary-and-guide-to-projections.html. You can choose the most appropriate for your workflow.

You can plot latitude and longitude points, e.g. 52.229588, 0.150855, using "geoshow" function as shown in documentation page in https://www.mathworks.com/help/map/ref/geoshow.html. Here is an example:

>> figure
>> geoax = axesm('pcarree');
>> geoshow('landareas.shp', 'FaceColor', [0.5 1.0 0.5]);
>> geoshow(52.229588, 0.150855, 'DisplayType', 'Point', 'Marker', '+', 'Color', 'red');
>> geoshow(42.301853, -71.376126, 'DisplayType', 'Point', 'Marker', '+', 'Color', 'red');

The figure will have a map which is draggable, and will have a red cross in Cambridge, UK. The figure allows to zoom in closer, to zoom out and to drag around the map.

Distance between two points in the Geographic Space You can calculate the distance between two points, as shown in documentation page in https://www.mathworks.com/help/map/calculate-distance-between-two-points-in-geographic-space.html, https://www.mathworks.com/help/map/ref/distance.html.

For the example, let us choose two GPS points:

52.229588, 0.150855 in Cambridge, UK.
42.301853, -71.376126 in Natick, MA, USA.

Then the arc length distance can be computed in this way:

[arclen, az] = distance([52.229588, 0.150855], [42.301853, -71.376126])
arclen =
   47.5027
az =
  287.9302

Then the distance can be calculated in kilometres using "deg2km" function as shown in documentation page in https://www.mathworks.com/help/map/ref/deg2km.html.

>> km = deg2km(arclen)
km =
   5.2821e+03

MATLAB: How to add an image on a map

First, you need the projection method.

Then you can use the projection method information to convert the (lat,lon) coordinate on the map to (x,y) coordinate on the figure.

Lastly, you can use the (x,y) coordinate information to add the image on the figure.

Please see the follow sample code:

%%create a map
worldmap([27 28.5],[127.5 129])
% get the default projection method
mstruct=gcm
% the map projection method is 'eqdconic'
% check these websites for the project method:
% https://www.mathworks.com/help/map/summary-and-guide-to-projections.html
% https://www.mathworks.com/help/map/eqdconic.html
% By using this projection information, you can convert (lat,lon) to (x,y)
% on the figure
myLat = 28;
myLon = 128;
[x, y] = mfwdtran(mstruct,myLat,myLon);
scatter(x,y,'ro')
hold on
%%image
eLat = 28;
eLong = 128;
sizeDeg = 0.25;
img = imread('peppers.png');
latlim=[eLat eLat+sizeDeg];
lonlim=[eLong eLong+sizeDeg];
% show the frame of the image, you can skip this step
[xlim, ylim] = mfwdtran(mstruct,latlim,lonlim);
plot([xlim(1) xlim(2) xlim(2) xlim(1) xlim(1)],[ylim(1) ylim(1) ylim(2) ylim(2) ylim(1)],'y-')
% show the image
R = maprefcells(xlim,ylim,size(img(:,:,1)));
mapshow(img,R)

Best Answer

Related Solutions

MATLAB: How to plot a map and calculate distance between two points in the Geographic Space

MATLAB: How to add an image on a map

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