Frequently Asked
Questions
Tools and Functions
Using the map and data
Computer/connection
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How do I view the map legend?
Click on the arrow next to “Legend” on the bottom right of the map to display the map legend. Click on the arrow again to collapse the legend.
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How can I find detailed information about a feature on the map?
Click on the feature of interest to make a box appear with
information about that feature. Click on the “X”in
the upper right corner of the box to close the box.
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How can I save or share a map?
Click the “Share” button on the bottom right of the map to expand the share menu. You can then share your map using Facebook or email. You can save your map by bookmarking it or by printing to pdf and saving it on your computer.
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How can I see a full list of
included data?
Click here for a full list of the available data.
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How can I learn more about the data in the map?
To access metadata (“information about the data”),
click on the title of the map and the metadata
will open in a new window. Metadata is all the information
that will help you better understand the data, and includes
details about the quality, source, and content of the data.
The use of metadata is standard in the GIS industry, and
the methods for reporting metadata used here are the standard
developed by the Federal
Geographic Data Committee (FGDC)
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The map displays the data
as a range. How can I get the actual numbers?
Click on a town or map feature to reveal detailed information.
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Why did you use these particular
data layers?
Our goals were to make the Institute's original research on breast cancer and the environment on Cape Cod publicly available and to make available other environmental, health and demographic data sets for MA. The data included in this version of the application are primarily publicly available data sets from the Environmental Protection Agency (EPA), Massachusetts Geographic Information System (MASS GIS), and the Massachusetts Department of Public Health (DPH).
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What data did you want to
include that you couldn't?
The goal of MassHEIS is to bring together geographic data on health effects and environmental pollutants so that potential relationships can be explored by the public and researchers. In the context of this project, environmental data are useful if they can be used to estimate pollutant exposures or evaluate relationships between human activities and environmental change (e.g., how does drinking water quality relate to the land uses within drinking water well recharge areas?). Health data are useful if they are systematically collected, can be expressed with reference to an expected frequency in the underlying population, and can be shared on a scale that is relevant to variations in pollutant exposures or demographic factors of interest. The data currently included in MassHEIS are the most relevant we were able to identify, but many of the included data sets have limitations. Data on many environmental and health features of interest are simply not available. For example, only limited data are available on prevalence of learning disabilities and autism; rates of many common cancers and health effects would be more informative if mapped by census tract rather than by town; and pollution monitoring data are extremely scarce. With a greater state and federal investment in public health tracking, more could be learned.
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Why do you include only Massachusetts?
MassHEIS was initially intended to provide public access
to health and environmental information from Silent Spring
Institute’s
Cape
Cod Breast Cancer and Environment Study. The
tool was later expanded to include available health, environmental
and demographic data for all towns in Massachusetts. The
data included in MassHEIS are primarily publicly available
data sets from the Environmental Protection Agency (EPA),
Massachusetts Geographic Information System (MASS GIS),
and the Massachusetts Department of Public Health (DPH).
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What is statistical significance
and why is it so important?
Statistical significance is a useful guideline in interpreting research findings because it assesses the likelihood that results are due to chance alone. Statistical significance is based on a number called a "p-value." By convention, results achieving a p-value less than 0.05 are called statistically significant, which simply means that there is one chance in 20 that the finding is due only to chance. The traditional cutoff for statistical significance of p less than 0.05 is arbitrary, and an Standardized Incidence Ratio (SIR) that approaches but does not attain statistical significance may still be of interest.
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How accurate is the data?
Because the data come from a number of different sources, the quality of the data can vary. Generally there are two components to the quality of information in GIS. The first is the accuracy of the geographic coordinates used to locate information relative to its actual location. Second is the accuracy of the attributes associated with the geographic point. The first component is unique to GISs while the second component would apply to any database. Different sources have different quality control mechanisms. Most of the data included in MASS HEIS comes from organizations with established quality control procedures and it is important to refer to the original source when evaluating data quality. By clicking on the data layer you can learn about the sources of other data sets included in HEIS and can follow the links back to the original sources.
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What are SIRs and why are they used rather than
rates?
Standardized Incidence Ratio, or SIR, is a common tool for monitoring disease rates. Incidence is the number of newly diagnosed cases in a given location during a given time period. An SIR compares the actual number of cases for a given place and time to the number that would be expected based on cancer rates in some comparison area. SIRs are usually written as 100 or 125 instead of 1.00 or 1.25. An SIR of 100 means that the actual number of cases equals the expected number. An SIR of 125 means that the actual number of cases was 25% higher than expected. An SIR of 75 means that the actual number of cases was only 75% of the expected number. For more information, see our glossary.
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What are limitations
of the data?
The quality of inferences that can be drawn from the
data depend on the quality of the original data. Information
in HEIS depends on varying sources of data, methods of
collecting and organizing data, scales of the data, and
completeness and accuracy of historical records. In addition,
Silent Spring Institute has followed standard practice
in not reporting cancer information where fewer than 5
cases appeared in a particular town or census tract in
a particular time period in order to protect the privacy
of individuals. We also only included data occurring with
a high enough frequency to be meaningful when mapped. For
example, Institute researchers determined that birth defects
are not prevalent enough to map at the municipal level,
given that such data have only been reported to the public
for a few years. In the future, it may be possible to map
birth defects by town by aggregating data over a longer
time
period. To learn more about any particular data layer,
click on the data layer.
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What does -999 mean?
Where data was not available or censored, the value -999 was substituted to clearly differentiate the record from those with real data. Silent Spring Institute is invested in protecting the privacy of individuals and has followed standard practice in censoring town level cancer data rates where fewer than five cases appeared in a particular time period.
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Why is some data displayed
as points and some as shapes?
Data for an area (e.g., town, census tract, county, or school district) are represented by a color shade for that area. Data related to a specific location (e.g., a factory) are represented as points. Most of the health data is represented as shapes and most of the environment data as points. Although the reported observation (e.g., cancer rate) for a municipality appears evenly distributed throughout the town, it may not be. Further, though much of the environmental data are represented by a single point or location on the map, that does not mean that the impact of the facility does not reach further than its immediate location. To protect privacy, health data that pinpoints individual cases is generally not released. Instead, health data are aggregated and displayed by census tract, block group, or town level.
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How can I find out where
the data came from, how it was collected, quality control
methods, and other information?
Metadata, "data about the data" is information that will help you better understand the data, and includes information about the quality, source, and content of the data. The use of metadata is standard in the GIS industry, and the methods for reporting metadata used here are the standard developed by the Federal Geographic Data Committee (FGDC) Most data sets include links back to their originating sources. To access metadata, click on the title of the map you are interested in.
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Why do the time frames
for the data sets vary?
Time frames for data sets we included are typically limited
by the source of the data. For example, cancer rates are
not available prior to 1982, when the MA Cancer Registry
was initiated. In some cases, we were able to provide more
extensive historical environmental data for Cape Cod as
a result of the Institute's original research, but good
quality historical data are largely unavailable electronically
for the rest of the state.
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Why is it difficult to compare
data?
It can be difficult to compare data over time and over
geographic areas because of varying sources of data, methods
of collecting and organizing data, scales of the data,
and completeness of historical records. For example, different
sources of data you may see on the maps include: breast
cancer statistics for your town from the Massachusetts
Cancer Registry; pesticide spraying data compiled by Silent
Spring Institute researchers; and toxic release data supplied
from the EPA’s Toxic Release Inventory (TRI) index.
You can learn more about the datasets by clicking on the
data layers.
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How can I/should I interpret
what I see?
Very carefully. Maps are a powerful tool for conveying
information, but they can be easily misinterpreted. When
interpreting a map that you have created, be sure that
you look carefully at the legend to confirm the range of
values each color represents. When creating a map with
multiple layers, pay close attention to the time frames.
While they do not have to be concurrent, you should consider
their time frames in making inferences about relationships
between factors. In addition, be aware of how the different
data sets we have provided were generated. Some, like hazardous
air pollutants, are models, or projections. Others, such
as asthma, are indicators of a phenomenon (e.g., asthma-related
hospitalizations), rather than an absolute measure (e.g.,
people in the town with asthma). Use the metadata feature
to learn the source of the data you are mapping. Finally,
variation is expected due to chance. Look for indications
of statistical significance, consistent trends over time,
and large sample sizes to determine if a phenomenon is
significant. We have gone to great lengths to attain the
best possible data sets for this project, however, they
do not communicate seamlessly. To make accurate inferences
using this mapping tool will require awareness on your
part of the data sets with which you are working.
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Should I cite a map and how
should I do it?
We ask users of MassHEIS to please cite the use of the
maps in your work. Citing data files and maps retrieved
from online sources is important for the following reasons:
• It is critical to acknowledge the authors and developers of a dataset,
whether published or unpublished;
• It is valuable for us, our funders, and our data sources to know that
the data and information we make available are useful to users;
• The inclusion of data citations is crucial to provide the relevant information
needed for users to confirm the accuracy and credibility of the data for further
information or analysis. The example below represents a method to cite the information;
however, publications often have their own style manuals, and we suggest you
check reference formatting instructions.
Maps (Dynamically Generated)
Identify the name of the mapping service as well as the name of the person
generating the map.
GENERAL FORMAT:
Author [if there is one]. "Map title" [format]. Scale. Computer database
title [format]. Edition. Place of production: Producer, Date of copyright or
production. Using: Author. Computer software title [format]. Edition.
Place of production: Producer, Date of copyright or production.
EXAMPLE:
"Massachusetts Breast Cancer Incidence 1995-2002" [map]. Scale 1" =
40 miles. Silent Spring Institute MassHEIS [computer files]. Anytown, MA: Jane
Doe, 2006. Using Silent Spring Institute MassHEIS [online application]. Newton,
MA: Silent Spring Institute. 2006.
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What
data will you include in the future?
Silent Spring Institute is currently working on adding blood lead data. Please use the Feedback box on the HEIS entry page to suggest other data sets you would like to be included in the future.
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___________________________________________________________________________________________ How do I use
ArcGIS with MassHEIS?
You can use ArcGIS to view and analyze MassHEIS data by using an ArcGIS Web Service. This will allow you to load the MassHEIS map services as 'layers' within ArcGIS, exposing them to the wide array of tools that are available with ESRI's ArcGIS suite. To load the services in ArcGIS, go to File - Add Layer - Add ArcGIS Server, and use the address: http://library.silentspring.org.
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What is the
ArcGIS Server address?
http://library.silentspring.org/ArcGIS/services
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How can I save data
to my own machine?
From the table view in MassHEIS, click the “Export to Table” button and save the file to your computer.
When viewing the layers as web services in ArcMap:
- select all or part of the layer you wish to save to your machine
- right-click and select'save as layer file'
- when the layer file appears in the menu, you can save as normal (i.e. data-export)
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Can
I look at information about the data without having to use the online application?
You may browse the data index to learn more about the data we are hosting.
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What coordinate
system is MassHEIS data presented in?
State Plane MA Mainland, NAD83 meters. This is the same
as MassGIS.
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