A information on learn how to make a personalized commuter’s map of your own home metropolis utilizing information science and Google Maps API
Final yr I acquired a job in Massachusetts on the Middle for Astrophysics in Cambridge. When on the lookout for close by flats, one among 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 through 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 submit particulars how I made the map and the way you are able to do one for your self. You’ll find the supply on GitHub.
Warning: If you wish to do the same venture (i.e., a map for a special vacation spot/metropolis) you need to get your individual API key. Google Maps permits you to do a average variety of calls without spending a dime per thirty days, so it’s attainable to do a venture like this without spending a dime. Nevertheless, you should be very cautious, it’s straightforward to go over the restrict after which be charged tons of of {dollars}.
Calculating Commute Occasions
Step one was to get a map of the Boston space 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 mechanically “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’ve got the grid, we simply must name Google Maps and use its Distance Matrix API to calculate the journey occasions to our vacation spot. Nevertheless, 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 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 venture 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 could 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 primarily signifies that I’d be prepared to return into work a bit sooner if meaning not ready on the bus cease for 20 minutes.
Commute Time overlaid on Metropolis Map
As soon as we’ve got the commute occasions for every grid level, we are able to visualize them on 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 as a result of construction of the MBTA community. For instance, residing 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 isn’t attainable to succeed in our vacation spot (e.g., prepare restore middle in East Cambridge).
Commute Distance of Boston Neighborhoods
Whereas this map is useful, it might be higher to have one thing we may use to filter outcomes from condo itemizing web sites. Most of those websites checklist which neighborhood every condo belongs to, permitting us to filter for it. So, it might 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 may attempt 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 path 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 can be crowding one another, some could have gaps between them). We are able to right 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_2dvor = 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 plotfor i,area in enumerate(vor.areas):shade = …polygon = [vor.vertices[k] for ok in area]plt.fill(*zip(*polygon),c=shade)
With this map we are able to rapidly see which neighborhoods are shut sufficient for us to commute from. Word that some areas in adjoining neighborhoods get combined (e.g., Downtown space). That is as a result of presence of excessive velocity public transportation (e.g., subway), which makes it sooner to commute from a station one cease additional than from an condo that could be a 5 minute stroll from the present station.
This venture started with me on the lookout for an condo 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. After all there are different concerns when shopping for an condo (hire, noise and many others.). In the long run I rented an condo 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.
