X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=doc%2Fproject_overview%2Findex.xhtml;h=f59e82f4c55456c1865a7cd8ff738b9ebb685416;hb=a288d4500730745bdd483c33c02411b9237b4a9f;hp=3201609ff353831172b13b440e926a270903e302;hpb=5bdd6e837232451fe5ae6dd9f726763587eb631e;p=dead%2Fcensus-tools.git diff --git a/doc/project_overview/index.xhtml b/doc/project_overview/index.xhtml index 3201609..f59e82f 100644 --- a/doc/project_overview/index.xhtml +++ b/doc/project_overview/index.xhtml @@ -30,7 +30,7 @@ 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 event taking place somewhere in the + associated with an event 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. @@ -75,6 +75,22 @@

    +
  1. + Most of the application code is written in Python, and so the Python + runtime is required to run it. + +
      +
    1. + We utilize a third-party library called Shapely 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. +
    2. +
    +
  2. +
  3. The build system utilizes GNU Make. The @@ -162,7 +178,7 @@
  4. - A redundant field, called blkidfp00, which contains the + A redundant field, called blkidfp00, which contains the concatenation of block/state/county/tract. This is our unique identifier.
  5. @@ -180,7 +196,7 @@ 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 - blkidfp00 identifier. + blkidfp00 identifier.

    @@ -198,8 +214,8 @@

    Note: the makefile 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.

    @@ -208,16 +224,16 @@

    A Postgres/PostGIS database is required to store our Census - data. The database name is unimportant (default: census), + data. The database name is unimportant (default: census), but several of the scripts refer to the table names. For - simplicity, we will call the database census from now on. + simplicity, we will call the database census from now on.

    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 lwpostgis.sql and - spatial_ref_sys.sql. See the lwpostgis.sql and + spatial_ref_sys.sql. See the makefile for an example of their import.

    @@ -254,12 +270,12 @@

    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, shp2pgsql, that will + database. PostGIS provides a binary, shp2pgsql, that will parse and convert the shapefiles to SQL.

    - There is one caveat here: the shp2pgsql program requires + There is one caveat here: the shp2pgsql 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 NAD83, or the North American Datum (1983). There may be @@ -326,7 +342,7 @@

    Switch from GiST to GIN Indexes

    - When the TIGER data is imported via shp2pgsql, a shp2pgsql, a GiST index is added to the geometry column by means of the -I flag. This improves the performance of the @@ -342,6 +358,47 @@ may be worth evaluating the benefit of a GIN index versus the GiST one.

    + +

    Related Projects

    + +

    Transportation Routing Analysis Geographic Information System (TRAGIS)

    +

    + TRAGIS is developed by the + Geographic Information Science & Tech Group at Oak Ridge + National Laboratory. From the abstract, +

    + +
    +

    + 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. +

    +
    + +

    + It is of interest to us because it provides routing subject to + HAZMAT and many other restrictions. Essentially, one provides + TRAGIS with starting point A and an end point + B; it then calculates the best route between + A and B, subject to a number of + constraints. +

    + +

    + 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 User Manual + does provide some clues as to where they have obtained their data, + though. +

    +