1. The Tufts University Institute for the Environment is looking to access where undergraduate
students live off campus, how far they commute to campus each day, and the quality of their
houses based on proximity to cultural resources. The positional accuracy of street centerlines
needs to be +/- 20 feet to provide a rough estimate of the commute distance and connectivity
needs to be 100% to accurately access the distance of the commute and distance from features
that improve quality of life. Data should be close to 100% complete and should accurately
reflect the surround areas by a year ago when students signed their leases.
2. The two road centerline datasets, one from MassGIS and TIGER, seem to be almost identical.
Luckily, for this project both sets of data are much within the +/- 20 feet threshold, with almost
all centerlines deviating no more than 10 feet. The main difference between the layers is that
the TIGER data seems to be a tad more complete, including a few roads on campus that are not
in the MassGIS layer. However, many of these additional roads are far less accurate that the
roads both layers have and could be better described as side streets. These additional roads
seem to decrease the accuracy of road centerlines and, thus I would use the MassGIS data in
this regard. In addition to improved positional accuracy for all roads, the MassGIS data also has
a much more complete attribute table that could be used to access quality of life standards by
using attributes such as road class. However, neither data set features house numbers, which
makes parcel data a necessity for mapping student addresses.
3. The hydrography layers from MassGIS and TIGER, like road centerlines, are nearly identical.
There are even fewer differences in the hydrography data. Positional accuracy seems generally
good. However, the water features are often not quite wide enough to span the whole river, by
up to 75 feet. However, this data is not very important to the project aside from being a
location of park land (which is mapped in other layers). Completeness seems to be at 100%, I
can locate no small water features that were missed in the campus area. While the
hydrography layers are much less important, only useful if students live on the other side of the
Mystic or Charles River, the TIGER attribute features a names of the water features, while
MassGIS does not and would make TIGER preferable for almost any use, regardless of their
otherwise overwhelming similarities.
4.1 I used the Parcel data obtained by Tufts for the city of Somerville to capture the locations of
students’ houses. Although I could not obtain a specific positional accuracy from its scale 9it
lacks any metadata), my analysis of some of the worst mistakes on the map seem to imply a +/10 foot error. Looking at the map, the data seems to cover all of Somerville and was last
updated in 2009 as the layer’s title implies. The attribute data has most of the addresses in the
city, there are a significant amount of blank addresses, but those are possibility empty lots or
other building-less properties. Overall the data is adequate to find the locations of students’
housing given their addresses and measuring the distance from those properties to the campus
center.
4.2 & 4.3
The help establish features the increase the quality of life for any given home, I downloaded the
Medford Parks Layer and the Somerville Parks Layer. Both lack metadata to judge positional
accuracy with, they seem to have positional accuracy within +/- 50 feet. However, given the
large size of the parks that accuracy is more than sufficient. The data seems to be relatively
current, Somerville layer’s title claims to be from 2005, but very few if any new parks have been
added in either city since 2000. Attributes are not really necessary for this project, but both
layers contain the names of parks. However, the main problem with these layers and why they
are unsuitable for this project is that they both have several large omissions. The Medford
layers any label for most of the Middlesex Fells park, which is among the largest urban parks in
the country or for the smaller Medford-Brooks Estate Land Trust. The Somerville Parks data
includes the Somerville Community Path, but omits the Minuteman/Alewife Bike Path and the
Davis Square Pedestrian Plaza, both important parks in Somerville. Because of its large
omissions these layers would not be suitable for this project.
4.4 For the last layer, I downloaded the MassGIS MBTA bus routes map to measure the
connectivity of off campus students to the rest of Boston. The positional accuracy of the routes
seem to mimic that of the MassGIS centerline data and its very high positionally accuracy (+/-10
feet). The map seems to be 100% complete compared with an MBTA bus map, and thus
currency is not very relevant. However, the way the routes are mapped roads with multiple
routes are mapped no differently than a single route. This hides some information, but does not
make the data unsuitable for this project. Attributes are also not necessary, but the route
numbers seem to be a bit off in the attribute table. Overall, this data is suitable for the project.