Beyond the Property Line is a data-driven service that leverages open-source data from various sources. This page provides information on the data sets we use.

Infrastructure Data

Beyond the Property Line currently provides map-level and modeling information on the following infrastructure types: airports, cell phone towers, electric substations, medical facilities, jails and prisons, landfills, oil and natural gas wells, and power plants. The geographic coordinates and metadata associated with these infrastructure types within the U.S. come from the U.S. Homeland Infrastructure Foundation-Level Data (HIFLD) Open Data website. The table below provides a link, access date, and brief summary of the data for each of the infrastructure types.

Infrastructure Access Date Notes
Airports February 21, 2022 Nearly 20,000 records of airports, heliports, and other aircraft landing facilities in the U.S. Data last updated January 9, 2022.
Cell Towers February 21, 2022 Over 24,000 records of cell phone towers in the U.S. Data last updated December 16, 2021.
Substations February 21, 2022 Nearly 78,000 records of electric substations in the U.S. Data updated on a near-continual basis.
Medical Facilities February 21, 2022 Nearly 69,000 records of hospitals, psychiatric care centers, and other medical care centers in the U.S. Data updated on a near-continual basis.
Jails / Prisons March 1, 2022 Over 6,700 records of secure detention facilities in the U.S. Data last updated February 17, 2022.
Landfills February 21, 2022 Nearly 7,400 records of solid waste landfill facilities in the U.S. Data last updated July 8, 2020.
Oil / Natural Gas Wells February 21, 2022 Over 1.5 million records of oil and natural gas wells in the U.S. Data last updated November 5, 2020.
Power Plants February 21, 2022 Nearly 12,000 records of power plants in the U.S. Data last updated July 9, 2020.

For all of the infrastructure types except for jails and prisons, specific latitude and longitude coordinates were provided in the data set. However, the data set for jails and prisons contained GIS boundaries. Therefore, for the purposes of mapping and calculating distance metrics for jails and prisons, we assigned latitude and longitude coordinates to each record in the jails and prisons data set by calculating the average of the minimum and maximum latitude and longitude values for the boundary, respectively.

Somerville, Massachusetts Modeling Data

Beyond the Property Line currently provides modeling results to help users assess the impact of infrastructure proximity on house value. The extent of this modeling is limited to addresses located in Somerville, MA because property assessor data for single-family homes in Somerville for the years 2015-2019 are made publicly available by the City of Somerville Assessor’s Office for fiscal years 2014-2019. The data set was last updated on July 1, 2020, and it can be accessed from the following link (as of March 22, 2022): https://data.somervillema.gov/Finance/Assessor-s-Property-Database-FY14-FY19/ubdh-uik5. For our modeling, we only used data for the single-family home parcels, of which there are 2,303 that contain data for all fiscal years.

The locations of the 2,303 single-family home parcels are shown in the interactive map below.

Exploratory Data Analysis

Combining the various infrastructure data sets with the Sommerville, MA data set allows us to explore the observed infrastructure proximity effects on single-family houses in Sommerville. The plot below shows the distribution of the minimum distance for each house in Somerville to the different infrastructure types (using a maximum search radius of 5 mi). From this plot we note a few observations:

Additionally, we can look at the distribution of assessed parcel values based on proximity to and count of the different infrastructure types. The box-and-whisker plot below shows this for the number of infrastructure instances located within 2 mi of the house for fiscal year 2019. Such a plot reveals other interesting observations (which are applicable to the specified 2 mi proximity radius):