How you can Discover an Residence with a Quick Commute | by Dávid Guszejnov

A information on methods to make a custom-made commuter’s map of your house metropolis utilizing information science and Google Maps API

Final 12 months I obtained a job in Massachusetts on the Center for Astrophysics in Cambridge. When searching for close by residences, one in all 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 traces, it was not apparent by which neighborhoods I ought to even be searching for residences. So I made a decision to make a map of the Larger Boston space exhibiting 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 the same challenge (i.e., a map for a distinct vacation spot/metropolis) it’s a must to get your personal 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 a whole lot of {dollars}.

Calculating Commute Occasions

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 are going to calculate the journey time. To cut 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. Word 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 street.

As soon as we now have the grid, we simply must name Google Maps and use its Distance Matrix API to calculate the journey occasions to our vacation spot. Nonetheless, there are a number of subtleties to remember when calculating journey occasions:

We have to specify the time of the day. Since I’d be commuting to my office throughout 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 cut 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 keen to come back 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 we now have the commute occasions for every grid level, we are able to visualize them on town map with a stuffed contour plot.

Map of Larger Boston coloured by commute time to the Heart of Astrophysics in Cambridge (blue cross); picture by writer

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 as a result of 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 want to take a bus and would get there later. There are additionally small islands from the place it’s not potential to succeed in 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 may use to filter outcomes from residence itemizing web sites. Most of those websites record 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.

Neighborhood map of the Boston space, x marks the situation of my office; picture by writer

We may strive to attract a map of the Boston neighborhoods the place the space 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 space of every pixel relative of the origin to be proportional to the commute time, whereas maintaining their relative course 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 can 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 okay in area]
plt.fill(*zip(*polygon),c=coloration)

Map of Boston neighborhoods scaled with commute time; picture by writer

With this map we are able to shortly see which neighborhoods are shut sufficient for us to commute from. Word that some areas in adjoining neighborhoods get blended (e.g., Downtown space). That is as a result of presence of excessive pace public transportation (e.g., subway), which makes it quicker to commute from a station one cease additional than from an residence that may be a 5 minute stroll from the present station.

This challenge started with me searching for an residence from which my commute wouldn’t be too lengthy(< 45 min). This implies I ought to primarily be searching for residences in Cambridge, Somerville, Belmont, Arlington, Allston, Watertown and the Downtown space. After all there are different concerns when shopping for an residence (lease, noise and so on.). 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 to your metropolis, take a look at the supply on GitHub.