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... using TIGER WMS and related shapefiles
... examining neighborhood weather using NOAA WMS & Census shapefiles
The section provides an introduction to use of the CV XE GIS with the Census Bureau TIGER Web Map Server (TIGERWMS). A separate part reviews how census tract shapefiles can be knitted together with the NOAA WMS to dynamically examine neighborhood weather patterns (near real-time data). Operations illustrated here may be performed using any version of CV XE GIS including the no fee version. The CVXE GIS installer includes files used in applications reviewed here. Install CVXE GIS now.
TIGERWMS is a Web-based resource that can be used to display Census Bureau political and statistical geography in map format down to the census block and street segment level. An advantage to using the TIGERWMS is that all of these geographies (including 11 million+ census blocks) are available through this single resource. TIGERWMS provides no direct access to demographic data. More technical details.
An Example: Geography in Vicinity of K-12 Schools
Consider a scenario ... we might seek to analyze demographic characteristics of census blocks, block groups and census tracts in the vicinity of one or a set of schools.
Congressional Districts. Compare/examine state legislative districts and congressional districts in a manner similar to that described here for schools and small area geography. Add recently enacted 113th Congressional District shapefiles to a CVXE project; examine relationship of other geographies to congressional districts.
This example uses Texas K-12 schools with a focus on the McKinney, TX area. See related McKinney ISD, TX applications. Similar applications can be performed for schools anywhere in the U.S. While schools are used here, businesses or locations of any type could be used.
With CVXE running Open>Favorites and select mckinney_tigerwms.gis. The start-up view is shown below.
In the above view, the legend panel (left section) shows four layers:
Census 2010 roads/streets shapefile (Census 2010 TIGER/Line Census edges shapefile for Collin County, TX)
Texas K-12 schools markers shapefile (from Texas Education Agency)
Census 2010 smoothed all U.S. counties shapefile (Census 2010 TIGER/Line shapefile
Tiger WMS -- itself showing many additional layers
Two schools are shown as red markers in the above map graphic. Burks El is in Census 2010 census block 2010 of census tract 307.02 (030702). Caldwell El is in Census 2010 census block 2000 of census tract 308.02 (030802). Click the Zoom-out by step button two times. The view now appears as shown below. Boundaries of the census tracts can now be seen.
In the above view, the TIGERWMS layers Countie Labels and Counties are checked on and visible. Scrolling down in the legend panel (left), it can be seen that four additional TIGERWMS layers are checked on: Census Blocks, Census Block Labels, Census Tracts and Census Tracts Labels. In the scroll-down, many layers were viewed that are not checked on. All of these layers are available.
Click the zoom out by step button one more time. The county name, Collin, now appears in the map.
Combining Shapefiles and TIGERWMS
Click the zoom out by step button one more time. The Collin County boundary is now visible as shown in the graphic below. The real power comes from combining shapefiles with TIGERWMS. The above view was becoming very busy. Using the GIS tools, the two schools can be isolated and viewed in context of the county/region. In the next view, the road shapefile has been checked off (top of legend panel). A query has been applied to the schools layer so that no labels are shown and only these two schools are selected.
This has been a "step 1" in the set-up for analysis of demographic characteristics of census blocks, block groups and census tracts in the vicinity of one or a set of schools. The census block codes, block group codes and census tracts framing the area for analysis are now known. Next steps include integrating the demographics into the shapefiles for pattern analysis.
Some Technical Details
As a Web Map Server (WMS), TIGERWMS uses raster graphics. Zooming in or out can render a "blurred" view and labels that may seem oddly offset. There is nothing technically wrong with the operation. Conversely, TIGER/Line shapefiles use vector graphics. When CVXE is used to open both vector-based shapefiles and a raster-based WMS in the same project, the vector geography will always appear to be more crisp and accurate. Labeling (e.g., the school labels) can be provided dynamically for vector-based shapefiles but cannot for a raster-based WMS. Fill patterns (e.g., showing demographic patterns) can be dynamically provided using vector-based shapefiles and are not available using a raster-based WMS. The detail and precision conveyed by shapefile layers is retained in all zoom levels.
Opening TIGERWMS only with CVXE shows the map view in non-projected WGS 84 coordinate system.
Opening the Texas schools shapefile with CVXE (NAD83 Texas Centric Lambert Conformal projection) and then TIGERWMS results in a view, including TIGERWMS, that follows the projection of the Texas schools shapefile.
Yet another option ... with both layers open, the overall project projection can be modified to select any projection. The Select Coordinate System button is clicked and the World Mercator projection is selected. Compare the Texas by county views below with the two above.
Blending Census and Other Shapefiles with NOAA WMS
... view political and statistical geography contextually with frequently updated Web-sourced data
The next view shows the same Texas schools layer (schools as blue markers), Census 2010 smoothed counties shapefile and National Oceanic and Atmospheric Adminstration (NOAA) WMS. More about the NOAA WMS. The NOAA WMS layer "Weather Radar Mosaic" is selected (details below, one of many WMS layers available). The project view is set to World Mercator.
Examining Neighborhoods & Weather Patterns
Adding census tracts ... the next view shows the Houston metro area, census tracts, counties with labels (all Census-sourced shapefiles), schools (shapefile) and weather patterns (NOAA WMS). The identify tool is used to show a mini-profile for a selected census tract/neighborhood area based on the Census 2010 census tracts shapefile (see pointer in tract selected). Census tracts shapefile could be augmented with demographics and weather attributes.
About the Weather Mosaic Layer
See this additional information about NOAA WMS layer legends:
- Weather radar mosaic color/dBZ legend: http://nowcoast.noaa.gov/LayerInfo?layer=RAS_RIDGE_NEXRAD&data=legend
- Weather radar mosaic last update: http://nowcoast.noaa.gov/LayerInfo?layer=RAS_RIDGE_NEXRAD&data=timestamp.
- More about layers in general: http://nowcoast.noaa.gov/LayerInfo?
In the weather mosaic legend, dBZ stands for decibels of Z. dBZ is a meteorological measure of equivalent reflectivity (Z) of a radar signal reflected off a remote object. Radar returns are usually described by color (as shown in the legend) or level. The colors in a radar image normally range from blue or green for weak returns, to red or magenta for very strong returns. The numbers in a verbal report increase with the severity of the returns. The U.S. National Doppler Radar sites use the following scale for different levels of reflectivity:
- magenta: 65 dBZ (extremely heavy precipitation, possible hail)
- red: 52 dBZ
- yellow: 36 dBZ
- green: 20 dBZ (light precipitation)
... on down to nothing
The TIGER WMS and NOAA WMS are included with the CV XE Installer. You can create views shown here and examine maps dynamically after installing CV XE. Install CVXE GIS now. .
Proximity develops geodemographic-economic data and analytical tools and helps organizations knit together and use diverse data in a decision-making and analytical framework. We develop custom demographic/economic estimates and projections, develop geographic and geocoded address files, and assist with impact and geospatial analyses. Wide-ranging organizations use our tools (software, data, methodologies) to analyze their own data integrated with other data. Contact Proximity (888-364-7656) with questions about data covered in this section or to discuss custom estimates, projections or analyses for your areas of interest.