Tag Archives: Shapefiles

Analyzing Block Group Demographics

.. tools & data to analyze sub-census tract households, education, income, housing, more … Block Groups, subdivisions of census tracts, are the smallest geographic areas for which “richer demographics” are developed by the Census Bureau. Block group demographic-economic estimates, based on Census 2010 geography, are annually updated beginning with American Community Survey (ACS) 2010. The latest ACS estimates for these 217,740 areas covering U.S. wall-to-wall are from ACS 2015. The ACS 2016 update will be released in December 2017.  See the related Web section for more detail about accessing and using block group geography and demographic-economic data.

Patterns of Economic Prosperity by Block Group
The following graphic shows patterns of median household income by block group in the Houston, TX area. Markers show block groups with 10 or more housing units having value of $2 million or more. Markers are labeled with the number of housing units having value of $2 million or more in that block group. Click graphic for larger view, more detail and legend color/data intervals. This map illustrates the geographic level of detail available using block group demographics and the relative ease to gain insights using geospatial data analytics tools.

– View developed using CV XE GIS and related GIS project.

Block Group Demographic-Economic Data & Shapefiles
… selection of key demographic-economic attributes; annual update
… subject matter categories include:
  • Total population>
  • Population by gender iterated by age
  • Population by race/origin
  • Households by type of household
  • Educational attainment by detailed category
  • Household Income by detailed category
  • Housing units by owner/renter occupancy
  • Housing units by units in structure
  • Housing units by detailed value intervals

See the related Web section for a detailed list of items.

Use these Data on Your Computer
Use the above U.S. national scope dataset with your own software or in ready-to-use GIS projects with the CV XE GIS software.

Join me in a Data Analytics Lab session to discuss more details about accessing and using wide-ranging demographic-economic data and data analytics. Learn more about using these data for areas and applications of interest.

About the Author
— Warren Glimpse is former senior Census Bureau statistician responsible for innovative data access and use operations. He is also the former associate director of the U.S. Office of Federal Statistical Policy and Standards for data access and use. He has more than 20 years of experience in the private sector developing data resources and tools for integration and analysis of geographic, demographic, economic and business data. Contact Warren. Join Warren on LinkedIn.

Developing Geographic Relationship Data

.. tools and methods to build and use geographic relationship files … which census blocks or block groups intersect with one or a set of school attendance zones (SAZ)? How to determine which counties are touched by a metropolitan area? Which are contained within a metropolitan area? Which pipelines having selected attributes pass through water in a designated geographic extent? This section reviews use of the Shp2Shp tool and methods to develop a geographic relationship file by relating any two separate otherwise unrelated shapefiles. See relasted Web page for a more detiled review of using Shp2Shp.

As an example, use Shp2Shp to view/determine block groups intersecting with custom defined study/market/service area(s) … the only practical method of obtaining these codes for demographic-economic analysis.

– the custom defined polygon was created using the CV XE GIS AddShapes tool.

Many geodemographic analyses require knowing how geometries geospatially relate to other geometries. Examples include congressional/legislative redistricting, sales/service territory management and school district attendance zones.

The CV XE GIS Shape-to-Shape (Shp2Shp) relational analysis feature provides many geospatial processing operations useful to meet these needs. Shp2Shp determines geographic/spatial relationships of shapes in two shapefiles and provides information to the user about these relationships. Shp2Shp uses the DE-9IM topological model and provides an extended array of geographic and subject matter for the spatially related geometries. Sh2Shp helps users extend visual analysis of geographically based subject matter. Examples:
• county(s) that touch (are adjacent to) a specified county.
• block groups(s) that touch (are adjacent to) a specified block group.
• census blocks correspond to a specified school attendance zone.
• attributes of block groups crossed by a delivery route.

Block Groups that Touch a Selected Block Group
The following graphic illustrates the results of using the Shp2Shp tool to determine which block groups touch block group 48-85-030530-2 — a block group located within McKinney, TX. Shp2Shp determines which block groups touch this block group, then selects/depicts (crosshatch pattern) these block groups in the corresponding GIS map view.

Geographic Reference File
In the process, Shp2Shp creates a geographic relationship file as illustrated below. There are six block groups touching the specified block group. As shown in the above view, one of these block groups touches only at one point. The table below (derived from the XLS file output by Shp2Shp) shows six rows corresponding to the six touching block groups. The table contains two columns; column one corresponds to the field GEOID from Layer 1 (the output field as specified in edit box 1.2 in above graphic) and column 2 corresponds to the field GEOID from Layer 2 (the output field as specified in edit box 2.2 in above graphic). The Layer 1 column has a constant value because a query was set (geoid=’480850305302′) as shown in edit box 1.3. in the above graphic. Any field in the layer dataset could have been chosen. The GEOID may be used more often for subsequent steps using the GRF and further described below. It is coincidental that both layers/shapefiles have the field named “GEOID”.

Layer 1 Layer 2
480850305302 480850305272
480850305302 480850305281
480850305302 480850305301
480850305302 480850305311
480850305302 480850305271
480850305302 480850305312

Note that in the above example, only the geocodes are output for each geography/shape meeting the type of geospatial relationship. Any filed within either shapefile may be selected for output (e.g., name, demographic-economic field value, etc.)

How it Works — Shp2Shp Operations
The following graphic shows the settings used to develop the map view shown above.

See related section providing details on using the Shp2Shp tool.

Geographic Relationships Supported
The Select Relationships dropdown shown in the above graphic is used to determine what type of spatial relationship is to be used. Options include:
• Equality
• Disjoint
• Intersect
• Touch
• Overlap
• Cross
• Within
• Contains
See more about the DE-9IM topological model used by Shp2Shp.

Try it Yourself

See full details on how you can use any version, including the no fee versin, of CV XE GIS to use the Shp2Shp tools. Here are two examples what you can d. Use any of the geospatial relatoinships. Apply your own queries.

Using Touch Operation
Select the type of geographic operation as Touch. Click Find Matches button. The map view now shows as:

Using Contains Operation
Click RevertAll button. Select the type of geographic operation as Contains. Click Find Matches button. The map view now shows as:

Relating Census Block and School Attendance Zones
The graphic shown below illustrates census blocks intersecting with Joyner Elementary School attendance zone located in Guilford County Schools, NC (see district profile). The attendance zone is shown with bold blue boundary. Joyner ES SAZ intersecting blocks are shown with black boundaries and labeled with Census 2010 total population (item P0010001 as described in table below graphic). Joyner ES is shown with red marker in lower right.


– view developed using CV XE GIS and related GIS project; click graphic for larger view

See more about this application in this related Web section.

Join me in a Data Analytics Lab session to discuss more details about accessing and using wide-ranging demographic-economic data and data analytics. Learn more about using these data for areas and applications of interest.

About the Author
— Warren Glimpse is former senior Census Bureau statistician responsible for innovative data access and use operations. He is also the former associate director of the U.S. Office of Federal Statistical Policy and Standards for data access and use. He has more than 20 years of experience in the private sector developing data resources and tools for integration and analysis of geographic, demographic, economic and business data. Contact Warren. Join Warren on LinkedIn.

Using CVXEGIS dBase Script Tool

.. shapefiles are the most widely used type of vector-based geodata file type used Geographic Information Systems GIS. The shapefile structure, comprised of a .shp (geometry), .dbf (dBase-subject matter), ,shx (index file associating shp and dbf records) and .prj (projection), is in the public domain, well documented and used by many mapping GIS tools.

Persistent Need to Process & Restructure dBase Files
Many shapefiles, such as the wide ranging political, statistical and topographic Census Bureau TIGER/Line shapefiles, become available with no subject matter content or limited scope content. There is a persistent need to process the dBase files (.dbf) associated with shapefiles … adding data, computing data, linking data, updating data, etc.

dBase, or dBASE or dbf, files have wide ranging appeal and use well beyond mapping and GIS applications. The simple and transportable structure makes them ideal for any type of textual or statistical data that is of conventional text or numeric form associated with data records with associated ID fields (social security number, member number, customer number, geocode, and many others) — where the need to support queries or develop relational data files structures is great. Compared to Excel, dBase files provide a smaller footprint, can be processed faster with some dBase application software and can support a larger number of records.

This section briefly outlines use of the CVXEGIS Script feature. The Script feature includes the ability to develop programming-like code to process dBase files.

There is no fee for the basic version of the Script feature. It can be used with any dBase file. The learning curve is almost nil. Install CVXEGIS and start using the tool.

Script Tool User Interface
Create, manage code interactively; run the script as a batch file.
Top section shows code; lower section shows selected output.

Join me in a Data Analytics Lab session to discuss more details about accessing and using wide-ranging demographic-economic data and data analytics. Learn more about using these data for areas and applications of interest.

About the Author
— Warren Glimpse is former senior Census Bureau statistician responsible for innovative data access and use operations. He is also the former associate director of the U.S. Office of Federal Statistical Policy and Standards for data access and use. He has more than 20 years of experience in the private sector developing data resources and tools for integration and analysis of geographic, demographic, economic and business data. Contact Warren. Join Warren on LinkedIn.

Integrating Political/Statistical Geography with OpenStreetMaps

OpenStreetMaps (OSM) is a collaborative project to create/maintain a free editable map of the world. The OSM Internet-based map resource is built by a community of people who contribute and maintain data about roads, local geography and much more, all over the world.

Houston, TX; Texas 113th Congressional District 29
The following view illustrates using a congressional district shapefile (blue boundary) in combination with OSM as a base layer.

GIS Applications Linking/Combining Shapefiles with OSM
This section illustrates viewing political/statistical geography in context of streets/roads shapefiles and/or Web-based street/ground coverage graphics. When using GIS tools to view census tracts (as one example) rendered through the use of shapefiles, there is often no convenient way to view the boundaries in context of roads/ground cover. There are two alternatives. One option is to add a layer using the corresponding streets/roads shapefile. This option has important features but is often difficult, time-consuming or not feasible as the roads shapefile coverages are organized in county units. Also roads shapefiles provide only part of the picture with respect to ground coverage. A second option is to use Web-based roads/ground coverage tiling services such as OpenStreetMap. Both options are reviewed here.

Georgia Metropolitan Statistical Areas shapefile overlay
Metropolitan areas are shown as brown boundaries in the following view.

The CV XE GIS software is used to view a census tracts shapefile/layer in context with 1) roads shapefile/layer and 2) Web-based OpenStreetMap (OSM) layer via OSM WMS (OGC Web Map Service). CV XE GIS supports the OGC WMS standard, which means that it can be used to open map layers from any properly functioning WMS server, including OSM WMS servers. Use of the OSM shown here is available at no cost and has global coverage. Tiling graphics are courtesy of MapQuest.

Honolulu, Hawaii with Census Tract Boundaries
The Hawaii census tracts boundaries (red) are shown in the following view.

Get Started Now
No registration or fees are required to use the CV XE GIS software with OSM. Run the CV XE GIS installer on a Windows-based computer and create views/applications such as those shown below. Make custom maps of your neighborhood or a city/country anywhere in the world.

New York City with Census Tract Boundaries
New York census tracts boundaries (red) are shown in the following view.

Atlanta, GA Region Diversity Patterns Neighborhood
Census tracts are colored based on value of the diversity index. See color patterns assigned based on diversity index values as shown in legend at left of the map. Blue tracts are most diverse; red tracts are least diverse. Tracts shown with black cross-hatched pattern are tracts with 50-percent or more Hispanic population. Transparency of the shapefile layer is set to 80% enabling the view of the OSM basemap layer.

About the Author
— Warren Glimpse, developer of the CV XE GIS software, is former senior Census Bureau statistician responsible for innovative data access and use operations. He is developer of the Columbia, MO GBF/DIME used as the prototype for the Census Bureau TIGER/Line system. He is also the former associate director of the U.S. Office of Federal Statistical Policy and Standards for data access and use. He has more than 20 years of experience in the private sector developing data resources and tools for integration and analysis of geographic, demographic, economic and business data.