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A information on how one can make a custom-made commuter’s map of your private home metropolis utilizing knowledge science and Google Maps API
Final 12 months I bought a job in Massachusetts on the Center for Astrophysics in Cambridge. When on the lookout for close by flats, one in every of my key necessities was that it shouldn’t take too lengthy to commute to work. Since Boston has a reasonably constructed up public transportation system (MBTA) with a number of subway strains, it was not apparent during which neighborhoods I ought to even be on the lookout for flats. So I made a decision to make a map of the Higher Boston space displaying how lengthy it takes to commute to my office throughout morning rush hour. This put up particulars how I made the map and the way you are able to do one for your self. Yow will discover the supply on GitHub.
Warning: If you wish to do an analogous challenge (i.e., a map for a unique vacation spot/metropolis) you need to get your individual API key. Google Maps means that you can do a reasonable variety of calls without cost monthly, so it’s potential to do a challenge like this without cost. Nonetheless, you should be very cautious, it’s simple to go over the restrict after which be charged lots of of {dollars}.
Calculating Commute Instances
Step one was to get a map of the Boston area and create a mapping between it and GPS coordinates (i.e., latitude and longitude for every pixel). On this map we are able to outline a grid of factors the place we’ll calculate the journey time. To scale back the variety of API calls I selected to make my grid factors extra dense close to the middle and fewer dense on the outskirts. Observe that Google Maps routinely “snaps” to close by roads, so we don’t want to fret about whether or not our grid factors are literally on a highway.
As soon as now we have the grid, we simply have to name Google Maps and use its Distance Matrix API to calculate the journey occasions to our vacation spot. Nonetheless, there are just a few subtleties to remember when calculating journey occasions:
- We have to specify the time of the day. Since I’d be commuting to my office in the course of the morning rush hour I set an arrival time of 9 AM.
- Google Maps can present journey occasions for driving, biking and taking public transportation. For my challenge I picked public transportation solely.
- Most types of public transportation are pretty rare within the US, even throughout rush hour (e.g., buses coming solely each quarter-hour). This will introduce an error in our journey time calculation, so to scale back its results I made a decision to calculate the journey occasions for two extra arrival occasions (8:45, 8:52) and take the minimal of the three values. This basically implies that I’d be prepared to return into work a bit sooner if which means not ready on the bus cease for 20 minutes.
Commute Time overlaid on Metropolis Map
As soon as now we have the commute occasions for every grid level, we are able to visualize them on the town map with a crammed contour plot.
As anticipated, commute time will increase with distance, however we are able to additionally discover anomalies, factors bodily additional being nearer by commute time. There are even embedded islands of decrease commute occasions. That is because of the construction of the MBTA community. For instance, dwelling close to the Kendall/MIT subway station we are able to get to our vacation spot inside 30 min, but when we lived a number of streets nearer to our vacation spot we would wish to take a bus and would get there later. There are additionally small islands from the place it’s not potential to achieve our vacation spot (e.g., prepare restore heart in East Cambridge).
Commute Distance of Boston Neighborhoods
Whereas this map is useful, it will be higher to have one thing we might use to filter outcomes from residence itemizing web sites. Most of those websites listing which neighborhood every residence belongs to, permitting us to filter for it. So, it will make sense for us to translate our commute time map right into a map of neighborhoods. First, let’s simply make a map of the Boston neighborhoods.
We might strive to attract a map of the Boston neighborhoods the place the gap of any level to my office (the brand new origin) is proportional to the commute time (as a substitute of the bodily distance). We are able to accomplish this by altering the gap of every pixel relative of the origin to be proportional to the commute time, whereas preserving their relative route the identical.
phi = np.arctan2(y_image,x_image)
x_new = commute_time * np.cos(phi)
y_new = commute_time * np.sin(phi)
This may distort the picture, and result in uneven pixel sizes (i.e., some pixels will likely be crowding one another, some could have gaps between them). We are able to appropriate for that by doing a Voronoi diagram and coloring the ensuing cells in accordance the the colour of the corresponding pixel.
from scipy.spatial import Voronoi, voronoi_plot_2d
vor = Voronoi(np.vstack((x_new,y_new)).T)
voronoi_plot_2d(vor,ax=ax,show_points=False,show_vertices=False,line_width=0.0)
...
#Colorize the Voronoi plot
for i,area in enumerate(vor.areas):
coloration = ...
polygon = [vor.vertices[k] for ok in area]
plt.fill(*zip(*polygon),c=coloration)
With this map we are able to shortly see which neighborhoods are shut sufficient for us to commute from. Observe that some areas in adjoining neighborhoods get combined (e.g., Downtown space). That is because of the presence of excessive pace public transportation (e.g., subway), which makes it sooner to commute from a station one cease additional than from an residence that could be a 5 minute stroll from the present station.
This challenge started with me on the lookout for an residence from which my commute wouldn’t be too lengthy(< 45 min). This implies I ought to primarily be on the lookout for flats in Cambridge, Somerville, Belmont, Arlington, Allston, Watertown and the Downtown space. In fact there are different issues when shopping for an residence (hire, noise and so forth.). In the long run I rented an residence close to the boundary of Cambridge and Arlington.
If you wish to attempt to do the identical on your metropolis, take a look at the supply on GitHub.
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