Marcus Rozbitsky
Assignment #4
UEP 232 – Intro to GIS
1. The project I am working on is an assessment of the educational facilities in the northern
part of Cambridge, MA around Massachusetts Avenue north of Porter Square and access
to those facilities. Accuracy of the data is important. It is important that the information
is up to date and that the facilities and MBTA service routes are accurate. If this data is
in correct parents could be sending their children to locations that no longer exist or are in
the wrong place causing distress and potential harm if the children find themselves lost.
2. I would not use the Tiger data for streets, they are poorly drawn on the map and many are
drawn at strange angles as well. It is interesting that the Tiger data and the USA Streets
both included the Somerville Community Path and the local city data from
Cambridge/Somerville does not and they both call it the Red Line Path, which I have
never heard it referred to as such. It is amazing that on my street, Gold Star Road, just
off of Mass Ave. the 3 street maps are over 50 feet apart in some parts. While not critical
for this project if you just select one data set, it could be critical for other projects. I now
understand why every parcel has to be surveyed at the time of sale. For this project I
think I would select the local Cambridge/Somerville street centerline data as it seems to
be the most accurate.
Marcus Rozbitsky
Assignment #4
UEP 232 – Intro to GIS
3. Here the two layers are drastically different. The Census data layer barely has any water
at all and the shapes are completely unnatural, they are simply triangles and trapezoids.
The Census layer also does not include Alewife Brook and other water bodies. While
again it is probably not critical for this project it could be for others and where children
are concerned it could be life threatening if a child can’t swim. I would use the local
Cambridge data layer again because it is more accurate.
Marcus Rozbitsky
Assignment #4
UEP 232 – Intro to GIS
4. The MA street data has a Scale denominator: 100000, which I assume means it is
accurate up to +/-166.67 feet. It is the only thing close to a source map scale for any of
the data layers. I would say it is impossible to provide a quantitative assessment of the
positional accuracy of the data layers without using GPS. I would not use this data to
build anything without surveying, but again with this project I think the data is probably
good enough for my purposes.
5. I would say the additional data layers are pretty accurate in some spots and really off in
others. The MBTA data matches the local Cambridge/Somerville data better than the
USA Street data and the MA state street data. It would make sense that the other local
data (open space, schools, etc.) also fit the local street data layers better as well. or Give
a qualitative assessment of positional accuracy of each of the four optional layers relative
to the other layers (e.g., do streets run through buildings? are schools in the correct
location along a road?).
6. The additional layers are not exactly accurate. The MA state data has the Muscular
Therapy Institute labeled as a college/university and located where the Peabody
Elementary School is located on Rindge Ave., yet is locate in the next block to the west.
Also it does not list the library that is located there. Instead the MA state data had two
“libraries” that are not “libraries”. One is WR Grace Construction Products and the other
is the Amnesty International regional office. This is pretty bad especially for a project
like mine that is looking for schools and libraries
7. The data is not complete. There are a lot of blanks on the attribute tables. There are
sometimes streets that look like they connect to another but don’t or vise versa.
8. Most of the data is not that current. Looking at the Meta Data, the most recent data is the
MBTA data layers from 2008, but the others are at least 10 years old, but even then I am
not sure if that is when these data layers were created.
Marcus Rozbitsky
Assignment #4
UEP 232 – Intro to GIS
9. As stated before the miss labeling of Amnesty International and WR Grace Construction
Products as libraries is a big error and I am not sure why they got labeled as libraries. My
project would need accurate information, especially on street names, street addresses and
address ranges. From what I can tell there do not seem to be any errors on the address
and street names in the area where I am looking.