Introduction to GIS
My firm has been hired to increase the bike infrastructure in Jamaica Plain, MA, specifically so that schoolchildren can ride to school using only bike lanes or bike paths. For the project to be successful, road maps must be up to date and accurate, as well as information on current bike lanes and bike paths. Entryways in to the schools will need to be clear so that we can understand where the children will be going to place their bikes, and information on schools needs to be up to date and accurate. The project will incorporate knowledge of current green space offerings to understand the optimal placement for the paths, but the accuracy of this information is less essential to the success of the project. Ideally, the bike paths will avoid current bus routes, as busses tend to be difficult to maneuver around as a cyclist, and children will be especially hard to see from the height of an MBTA bus. All information should be up to date, so that planning energy is not wasted on out of date information.
2010 Census TIGER Road Layer:
For the most part, these lines look useful for our purposes, however, some of the more complicated intersections are where we see the breakdown of accuracy. For example, Egleston Square is an especially complicated and dangerous intersection for cyclists. The screen shot below shows how the lines from the Census go straight through a median. If the plan were to install bike lanes in this area, the planners shouldn’t have to worry about this error, as the painters will be on the ground and can see that they should not go over the median. However, if we were planning a raised bike path or a separated bikeway, this might become more problematic as these are more complicated projects that require more planning before installation.
Additionally, there are a few points in which this layer is inconsistent in how it displays the entrances to schools. See below for a demonstration of how one school with two entrances is shown with no specificity of how to enter, while another school is shown with a road going right through it. This makes it difficult to prioritize the proper route for the entry ways of the schools, as we don’t know how the kids will be getting in to the schools.
The MassGIS Road data set does line up with the aerial street view. The layer is up to date through April 3, 2012. Although there is some wiggle between the parameters of the aerial view, the lines from MassGIS are drawn at a scale of 1:5,000, which gives us an accuracies of +/- 13.33 feet. As you can see from the image below, the MassGIS data set, shown in purple, shows a much more accurate and useful picture of Egleston Square.
Additionally, the MassGIS data set is more consistent with the treatment of entryways:
For our purposes, the MassGIS data set is just enough more accurate and complete to use instead of the Census TIGER data set. Additionally, the Census data set is 2 years older, and it makes sense to use the most up to date road information available for this road based project.
The Census TIGER 2012 Hydrography data set is incomplete. Notably, it is missing the Brookline reservoir:
However, as our project is in Jamaica Plain and not Brookline, this is not a significant problem. You can see that the ponds are off by +/- 40 feet or so when you look at the edges of the larger Jamaica Pond and see the aerial photography showing edges that are not covered by the data set.
There are other places where the Census data set misses a few ponds. In the below screen shot, the light blue lakes are demonstrated by the MassGIS data set while the dark blue lakes are the ones that both data sets display. Again, these ponds are in areas that are not particularly essential to our project—they are either private ponds or located in parks, but it is worth noting that the MassGIS data set is more thorough than the Census:
The MassDEP Hydrography Layer is at a 1:25,000 ratio. Although it is older than the Census data (2010 v, 2012), it is more complete, and thus would be the layer I’d choose to use for the project.
MassGIS Data - Bicycle Trails:
The Bicycle trail map was created in 1997 and was updated in 2002. The data shows trails that allow bicycles, but not necessarily exclusively bicycles. Additionally, the data set does not show bicycle lanes that have been added to streets, which would be the most useful data for this project. As a cyclist in the neighborhood, I know that there are extensive networks of bike lanes in Jamaica Plain that should be included in this map. As it stands, this data set is not very useful to our project because it is so sparsely populated with bicycle infrastructure. The bike routes do look accurate. For our scale, the data should be reliable.
MassGIS Data - MBTA Bus Routes and Stops:
This data is based on the MBTA bus routes as of May 2007, which represents a significant problem. The MBTA has changed its service in Jamaica Plain in response to budget cuts, so many of the displayed routes are no longer in service. The metadata does not specify a scale at which the data is represented. The data does cover the area in question, and looks complete for the May 2007 bus routes as far as I can tell by using my memory. Because the data is outdated, we could not use this data set to get an accurate idea of current bus routes in the neighborhood. If this layer were more up to date, the attribute table would be quite helpful to understand which routes we are looking at, which could help figure out which routes might be running during school open/closing hours.
MassGIS Data – Protected and Recreational OpenSpace:
The attribute table for this layer is informative and shows us useful information for our purposes, such as who manages the open space and what special features might exist on the parks. The OpenSpace poly underwent major revisions in January of 2005. The website shows September 2013 on the map’s MetaData, but does not specify what happened in September of 2013. Although this may be a relatively outdated poly, open space tends to be fairly stable. However, I would want to do a walk through of Jamaica Plain to ensure that the map is accurate before using it for our project. If we could use the OpenSpace poly to emphasize routes with ample green space, we could create a really nice network of bike infrastructure for children to use to get to school. Each section of the OpenSpace Poly is done locally, so there is no information on a standard scale to understand the positional accuracy with clarity.
MassGIS Data – Schools (PK – High School):
This layer was updated based on information from February of 2012, so it should be updated enough for our purposes. The data set was created using address-matching and manually refined using the imagery to create an accurate map. The placement of the points would be more useful if it were at the entryways, but for the most part each point is on the building, which is helpful for our purposes. The information contained in the attribute table is thorough, including addresses, grades, phone numbers, fax numbers, and names of principals. The data set covers all of Jamaica Plain, and from the meta data’s description it does seem to be accurate information.