Where we take the data and how we process it
The Chicago Transit Authority provides a developer API that allows third party applications to download near realtime data (usually they have a delay around 30 seconds).
In this application we used the bus tracker API. In order to display realtime bus locations and stops for every bus the application needs to download the entire transport network and than display data only for the selected area. Since the API doesn't provide a filter based on the location of the bus every time the user selects an area the application will search in the entire network (using an efficient algorithm) for bus lines that have at least one stop inside the area. The creation of the network is a very slow process and for that reason we decided to save the precomputed network in a json file that is loaded when the application is launched.
For more informations please refer to the ufficial documentation.
The Divvybikes provide a realtime API that is updated near realtime (every 30 seconds) and gives the information about every station (number of bikes that are at that station and number of available docks).
You can find the data in JSON format here.
The application uses different data of Chicago, all of these data are downloaded in real-time from the City of Chicago Data Portal. In particular the list of the source for each data set is reported below:
Reports of potholes through the 311 call center and uses a computerized mapping and tracking system to identify pothole locations. Other than filtering for time and location no more elaboration has been performed for this data set.
All open abandoned vehicle complaints made to 311. Other than filtering for time and location no more elaboration has been performed for this data set.
All open reports of "Street Lights - All Out" (an outage of 3 or more lights) made to 311. Other than filtering for time and location no more elaboration has been performed for this data set.
All open 311 reports of one or two lights out on metal poles on a residential or arterial street. Other than filtering for time and location no more elaboration has been performed for this data set.
All reported incidents of crime (with the exception of murders where data exists for each victim) that occurred in the City of Chicago from 2001 to present, minus the most recent seven days. These data have been elaborated in order to have a better visualization, in the application all the original types of crime have been included in four principal categories composed in the following way:
Inspections of restaurants and other food establishments in Chicago from January 1, 2010 to the present. Other than filtering for time and location no more elaboration has been performed for this data set. Anyway the application automatically tries to match the locals deriving from yelp and the food inspection.
The Yelp developer API is the main source of information for restaurants and bars. We also itegrated information about food inspection failed. In order to do it the application uses the 311 data and a special software componet execute the merge of the data based on location (we tried also ann association name based, but it doesn't work very well since restaurant name can be in different languages in 311 database and Yelp).
The important places data was created using our knowledge of Chicago and manually aggregating data from external sources: Wikipedia and www.aviewoncities.com. This data doesn't require pre-processing because the application only needs the name of the place and its coordinates.
For the graphs has been mainly used the data proposed above, anyway the application shows graphics for some data set using density based on population (for what concerns crimes) or surface (for the other cases). With this approach is possible to compare the data from the city of chicago and the current selection in a "fair" way avoiding comparison between data regarding population or suface with high differences. The surface of the current selection has been computed using the geographic coordinates. For what concerns the population the application estimate it using the data relatives at the Population by 2010 Census Block and using the data relative at the census block boundaries avaible at the following link.