One of the foremost goals that must be achieved is to model the
average population density throughout the United States. Using
this data, we would like to be able to calculate the risk
- associated with an <em>event</em> taking place somewhere in the
+ associated with an <q>event</q> taking place somewhere in the
United States. This will, in general, be an accident or other
unexpected event that causes some damage to the surrounding
population and environment.
</p>
<ol>
+ <li>
+ Most of the application code is written in <a
+ href="http://www.python.org/">Python</a>, and so the Python
+ runtime is required to run it.
+
+ <ol>
+ <li>
+ We utilize a third-party library called <a
+ href="http://pypi.python.org/pypi/Shapely">Shapely</a> for
+ Python/GEOS integration. GEOS is required by PostGIS (see
+ below), so it is not listed as a separate requirement, even
+ though Shapely does depend on it.
+ </li>
+ </ol>
+ </li>
+
<li>
The build system utilizes <a
href="http://www.gnu.org/software/make/">GNU Make</a>. The
</li>
<li>
- A redundant field, called <em>blkidfp00</em>, which contains the
+ A redundant field, called <q>blkidfp00</q>, which contains the
concatenation of block/state/county/tract. This is our unique
identifier.
</li>
We need to correlate the TIGER/Line geometric information with the
demographic information contained in the Summary File 1 geographic
header records. To do this, we need to rely on the unique
- <em>blkidfp00</em> identifier.
+ <q>blkidfp00</q> identifier.
</p>
<p>
<p>
<em>
Note: the <a href="../../makefile">makefile</a> provides a task
- for creation/import of the databases, but its use is strictly
- required.
+ for creation/import of the databases, but its use is not
+ strictly required.
</em>
</p>
<p>
A Postgres/PostGIS database is required to store our Census
- data. The database name is unimportant (default: <em>census</em>),
+ data. The database name is unimportant (default: <q>census</q>),
but several of the scripts refer to the table names. For
- simplicity, we will call the database <em>census</em> from now on.
+ simplicity, we will call the database <q>census</q> from now on.
</p>
<p>
Once the database has been created, we need to import two PostGIS
tables so that we can support the GIS functionality. These two
- files are <em>lwpostgis.sql</em> and
- <
em>spatial_ref_sys.sql</em>. See the <a
+ files are <q>lwpostgis.sql</q> and
+ <
q>spatial_ref_sys.sql</q>. See the <a
href="../../makefile">makefile</a> for an example of their import.
</p>
<p>
Since the shapefiles are in a standard format, we can use
pre-existing tools to import the data in to our SQL
- database. PostGIS provides a binary, <em>shp2pgsql</em>, that will
+ database. PostGIS provides a binary, <q>shp2pgsql</q>, that will
parse and convert the shapefiles to SQL.
</p>
<p>
- There is one caveat here: the <em>shp2pgsql</em> program requires
+ There is one caveat here: the <q>shp2pgsql</q> program requires
an SRID as an argument; this SRID is assigned to each record it
imports. We have designated an SRID of 4269, which denotes
<q>NAD83</q>, or the North American Datum (1983). There may be
<h3>Switch from GiST to GIN Indexes</h3>
<p>
- When the TIGER data is imported via <
em>shp2pgsql</em>, a <a
+ When the TIGER data is imported via <
q>shp2pgsql</q>, a <a
href="http://www.postgresql.org/docs/8.4/static/textsearch-indexes.html">GiST</a>
index is added to the geometry column by means of the
<strong>-I</strong> flag. This improves the performance of the
may be worth evaluating the benefit of a GIN index versus the GiST
one.
</p>
+
+ <h2>Related Projects</h2>
+
+ <h3>Transportation Routing Analysis Geographic Information System (TRAGIS)</h3>
+ <p>
+ <a href="https://tragis.ornl.gov/">TRAGIS</a> is developed by the
+ Geographic Information Science & Tech Group at Oak Ridge
+ National Laboratory. From the abstract,
+ </p>
+
+ <blockquote>
+ <p>
+ The Transportation Routing Analysis Geographic Information
+ System (TRAGIS) model is used to calculate highway, rail, or
+ waterway routes within the United States. TRAGIS is a
+ client-server application with the user interface and map data
+ files residing on the user’s personal computer and the routing
+ engine and network data files on a network server. The user’s
+ manual provides documentation on installation and the use of the
+ many features of the model.
+ </p>
+ </blockquote>
+
+ <p>
+ It is of interest to us because it provides routing subject to
+ HAZMAT and many other restrictions. Essentially, one provides
+ TRAGIS with starting point <strong>A</strong> and an end point
+ <strong>B</strong>; it then calculates the best route between
+ <strong>A</strong> and <strong>B</strong>, subject to a number of
+ constraints.
+ </p>
+
+ <p>
+ Unfortunately, TRAGIS is a client/server application. Most of the
+ interesting logic and data are stored on the server, to which we
+ don't have access. The <a
+ href="https://tragis.ornl.gov/TRAGISmanual.pdf">User Manual</a>
+ does provide some clues as to where they have obtained their data,
+ though.
+ </p>
+
</body>
</html>
projects / dead / census-tools.git / blobdiff