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This example shows how to collect position data from an Android™ or iOS mobile device and display it on a map. Latitude and longitude coordinates are used to mark the device's route. Speed information is used to add color to the route. The final result is a visual representation of location and speed for the device's journey.
This example requires Mapping Toolbox™.
In order to receive data from a mobile device in MATLAB®, you will need to install and set up the MATLAB Mobile™ app on your mobile device.
Log in to the MathWorks® Cloud from the MATLAB Mobile Settings.
On the Commands screen of MATLAB Mobile, use the
mobiledev command to create an object that represents your mobile device.
m = mobiledev;
The displayed output should show
Connected: 1, indicating that the
mobiledev object has successfully established a connection to the app.
In order to collect GPS data, first ensure that your device's GPS is turned on. If enabled on the mobile device's location settings, mobile networks and Wi-Fi can also be used to determine position.
Enable the position sensor on your mobile device.
m.PositionSensorEnabled = 1;
It may take some time for data to appear on the Sensors screen of MATLAB Mobile, as the device will need to search for a GPS signal. GPS signals are generally unavailable indoors.
After enabling the sensors, the Sensors screen of MATLAB Mobile will show the current data measured by the sensors. The
Logging property allows you to begin sending sensor data to
m.Logging = 1;
All position sensor data recorded on the device is now being logged by
In this example, the device was taken on a short drive around MathWorks.
mobiledev's logging property again to stop logging data.
m.Logging = 0;
To create the map, latitude, longitude, and speed data will be needed. The
poslog function can be used to retrieve this information from
[lat,lon,t,spd] = poslog(m);
For this example, data has already been logged and saved.
load drivingAroundMathWorks lat lon spd;
The speed values are binned in order to use a discrete number of colors to represent the observed speeds.
nBins = 10; binSpacing = (max(spd) - min(spd))/nBins; binRanges = min(spd):binSpacing:max(spd)-binSpacing; % Add an inf to binRanges to enclose the values above the last bin. binRanges(end+1) = inf; % |histc| determines which bin each speed value falls into. [~, spdBins] = histc(spd, binRanges);
A discontinuous line segment is created for every speed bin. Each of these segments will be assigned a single color. This creates far fewer total line segments than treating every adjacent pair of latitude and longitude values as their own line segments.
The individual segments are stored as geographic features using
geoshape from Mapping Toolbox.
lat = lat'; lon = lon'; spdBins = spdBins'; % Create a geographical shape vector, which stores the line segments as % features. s = geoshape(); for k = 1:nBins % Keep only the lat/lon values which match the current bin. Leave the % rest as NaN, which are interpreted as breaks in the line segments. latValid = nan(1, length(lat)); latValid(spdBins==k) = lat(spdBins==k); lonValid = nan(1, length(lon)); lonValid(spdBins==k) = lon(spdBins==k); % To make the path continuous despite being segmented into different % colors, the lat/lon values that occur after transitioning from the % current speed bin to another speed bin will need to be kept. transitions = [diff(spdBins) 0]; insertionInd = find(spdBins==k & transitions~=0) + 1; % Preallocate space for and insert the extra lat/lon values. latSeg = zeros(1, length(latValid) + length(insertionInd)); latSeg(insertionInd + (0:length(insertionInd)-1)) = lat(insertionInd); latSeg(~latSeg) = latValid; lonSeg = zeros(1, length(lonValid) + length(insertionInd)); lonSeg(insertionInd + (0:length(insertionInd)-1)) = lon(insertionInd); lonSeg(~lonSeg) = lonValid; % Add the lat/lon segments to the geographic shape vector. s(k) = geoshape(latSeg, lonSeg); end
The pieces can now be combined into a webmap display. The latitude and longitude data have been processed to make up individual line segments to overlay on the map. Each line segment has a color corresponding to the speed recorded at the respective position.
Mapping Toolbox provides a number of functions for working with web maps.
webmap to open a web map in a browser.
wm = webmap('Open Street Map');
For reference, MathWorks is marked on the map.
mwLat = 42.299827; mwLon = -71.350273; name = 'MathWorks'; iconDir = fullfile(matlabroot,'toolbox','matlab','icons'); iconFilename = fullfile(iconDir, 'matlabicon.gif'); wmmarker(mwLat, mwLon, 'FeatureName', name, 'Icon', iconFilename);
A list of colors corresponding to the speed bins is generated using the
autumn colormap. This creates an
[nBins x 3] matrix with RGB values for each bin.
colors = autumn(nBins);
A line is drawn on the webmap using the geographic shape vector. Each element of the shape vector corresponds to a discontinuous line segment for a binned speed value. These elements match the elements of the color list that was just created.
wmline(s, 'Color', colors, 'Width', 5);
Zoom the map in on the route.
The final display provides a visual representation of location and speed throughout the route. The device was clearly traveling more slowly while in the parking lot and during turns than it was on straightaways.
Turn off the position sensor and clear
m.PositionSensorEnabled = 0; clear m;