CAMS Data (October 2011)

Current data date: August 2012 – we will be releasing new versions of this data periodically.

Important note: This file is not final – it is an intermediate step and should be used with the understanding that further work is being performed.

False Match Progress – June 12 [...]]]>

CAMS Data (October 2011)

Current data date: August 2012 – we will be releasing new versions of this data periodically.

Important note: This file is not final – it is an intermediate step and should be used with the understanding that further work is being performed.

False Match Progress – June 12 2013

Description

The LA County Street Center TIGER road file is a street centerline network in development by Los Angeles County to move toward a public domain street centerline and addess file.  This dataset can be used for two purposes:

1. Geocoding addresses in LA County – this file currently geocodes > 99.5% of the addresses in our test files (5,000 out of 8 million addresses) using the County’s geocoding engines.
   1. This last statement is important - the County splits the street names and addresses differently than most geocoders.  This means that you cannot just use this dataset with the standard ESRI geocoding (US Streets) geocoding engine.  You can standardize the data to resolve this, and we will be publishing the related geocoding rules and engines along with instructions on how to use them, in the near future.  Please review the data fields to understand this information.
2. Mapping street centerlines in LA County – note that the street types in this file are not fully updated yet.  Use with caution.

History

LA County has historically licensed the Thomas Brothers Street Centerline file, and over the past 10 years has made close to 50,000 changes to that file.  In order to provide better opportunities for collaboration and sharing among government entities in LA County, we have embarked upon an ambitious project to leverage the 2010 TIGER roads file as provided by the Census Bureau and upgrade it to the same spatial and attribute accuracy as the current files we use.  This effort is part of the Countywide Address Management System (click the link for details).

Processes

The County downloaded and evaluated the 2010 TIGER file (more information on that file, including download, is at this link).  The evaluation showed that the TIGER road file was the best candidate to serve as a starting point for our transition.

Since that time, the County is moving down a path toward a complete transition to an updated version of that file.  Here are the steps that have been completed and are anticipated.

1. Upgrade the geocoding accuracy to meet the current LA County street file licensed from Thomas Brothers.  This has been completed by the Registrar/Recorder (RRCC) – matching rate have improved dramatically. COMPLETE
2. Develop a countywide street type code to reflect various street types we use.  We have used various sources, including the Census CFCC and MTFCC codes to develop this coding.  The final draft is here –  Final Draft of Street Type Codes for CAMS (excel file)
3. Update the street type information to support high-quality cartography.  IN PROGRESS - we have completed an automated assignment for this, but RRCC will be manually checking all street segments in the County to confirm.
4. Load this dataset into our currrent management system and begin continuing maintenance.

NHGIS Site

The National Historical Geographic Information System (NHGIS) website recently is an incredibly valuable tool for historic demographics information. You just need to register.

From their site:

The National Historical Geographic Information System (NHGIS) provides, free of charge, aggregate census data and GIS-compatible boundary files for the United States between [...]]]>

NHGIS Site

The National Historical Geographic Information System (NHGIS) website recently is an incredibly valuable tool for historic demographics information.  You just need to register.

From their site:

The National Historical Geographic Information System (NHGIS) provides, free of charge, aggregate census data and GIS-compatible boundary files for the United States between 1790 and 2000. NHGIS offers the following options to obtain data:

The Census Bureau (http://www.census.gov/) maintains geographic boundaries for the analysis and mapping of demographic information across the United States. Every 10 years the Census Bureau counts the population of the United States as mandated by Constitution. The Census Bureau releases the results of this county as demographic data with [...]]]> Census Geography Background

The Census Bureau (http://www.census.gov/) maintains geographic boundaries for the analysis and mapping of demographic information across the United States. Every 10 years the Census Bureau counts the population of the United States as mandated by Constitution. The Census Bureau releases the results of this county as demographic data with geographic identifiers so that maps and analysis can be performed on the US population.

For a quick introduction to Census geography, click the thumbnail on the right which shows the relationship between Census Blocks, Block Groups, Tracts, and Counties.

For detailed information about the Census Geography, here are some other links:

• Geographic Shapefile Concepts Overview
• TIGER/Line Shapefile home page
• TIGER/Line Shapefile technical documentation

LA County Samples

Countywide	CSU LA
Census Blocks 2010	Zoomed at CSULA

What is unique about LA County’s data?

1. It is clipped to the ocean boundary. Raw Census data includes a 3 mile buffer into the ocean, which impacts cartography.
2. Each census blocks are assigned with the community name based on the 2011 redistricting unit community names.
3. IMPORTANT! It has been updated to re-include Census Tract 1370.00, which the Census Bureau mistakenly merged with tract 8002.04. Note – until the Census Bureau releases updated population files this update will impact population mapping since population tables will not have 13700.00 (it’s population will be part of 8002.04 showing higher numbers than reality). Please see this post on the County Enterprise GIS about this. We have included the raw file for those who want to use it.

Maps showing what changed

General Area	Zoomed in

How was this data created?

This data was downloaded from Census Bureau website: ftp://ftp2.census.gov/geo/pvs/tiger2010st/06_California/06037/ and clipped to the County Boundary using ESRI’s ArcGIS Desktop. A new field “COMMNAME” was added and populated with city and community names based on 2011 redistricting unit community names in the census block data. This dataset has unique identifier field “GEOID10” for each record, and the census tract and census block number combined field “CTCB10”, block group field “BG10” and census block number field “CB10”.

Download/Access the data

• 2010 Census Blocks.lyr (ArcGIS 10 layer file)- for LA County staff with access to the GIS Repository
• LA County updated Block File – cb2010.shp (zipped shapefile)
• 2010 Census Blocks (zipped original tiger shapefile) – CB2010_Tiger - this is the original file before the changes to Tracts 8002.04 and 1370.00

The Census Bureau (http://www.census.gov/) maintains geographic boundaries for the analysis and mapping of demographic information across the United States. Every 10 years the Census Bureau counts the population of the United States as mandated by Constitution. The Census Bureau releases the results of this county as demographic data with geographic [...]]]> Census Geography Background

The Census Bureau (http://www.census.gov/) maintains geographic boundaries for the analysis and mapping of demographic information across the United States.  Every 10 years the Census Bureau counts the population of the United States as mandated by Constitution.  The Census Bureau releases the results of this county as demographic data with geographic identifiers so that maps and analysis can be performed on the US population.

For a quick introduction to Census geography, click the thumbnail on the right which shows the relationship between Census Blocks, Block Groups, Tracts, and Counties.

For detailed information about the Census Geography, here are some other links:

• Geographic Shapefile Concepts Overview
• TIGER/Line Shapefile home page
• TIGER/Line Shapefile technical documentation

LA County Samples

Countywide	Downtown
Census Tracts 2010	Zoomed at Downtown LA

What is unique about LA County’s data?

1. It  is clipped to the ocean boundary.  Raw Census data includes a 3 mile buffer into the ocean, which impacts cartography.
2. IMPORTANT! It has been updated to re-include Census Tract 1370.00, which the Census Bureau mistakenly merged with tract 8002.04.  Note – until the Census Bureau releases updated population files this update will impact population mapping since population tables will not have 13700.00 (it’s population will be part of 8002.04 showing higher numbers than reality). Please see this post on the County Enterprise GIS about this.  We have included the raw file for those who want to use it.

Maps showing what changed

General Area	Zoomed in

How was this data created?

This data was downloaded from Census Bureau website: http://www.census.gov/cgi-bin/geo/shapefiles2010/file-download and clipped to the County Boundary using  ESRI’s ArcGIS Desktop.  Two new fields were added in census tract data – area in square feet and area in square miles. This dataset has unique identifier field “GEOID10” for each record and the census tract number fields “CT10” and “LABEL” (6-digit number and 6-digit number with decimal point, respectively).

Download/Access the data

• 2010 Census Tracts.lyr (ArcMap 10 Layer File) – for LA County staff with access to the GIS Repository
  
• LA County updated Tract File – ct2010.shp (zipped shapefile)
• Original 2010 Census Tract File – ct2010_original.shp (zipped shapefile) – this is the original file before the changes to Tract 8002.04 and 1370.00

Historically this file has had a number of identified issues with its geographic accuracy, but the 2010 file has been tested by LA County and found to be highly accurate [...]]]> The TIGER road file is a street centerline network used by the US Census Bureau to help locate and find citizens during its decennial census.

Historically this file has had a number of identified issues with its geographic accuracy, but the 2010 file has been tested by LA County and found to be highly accurate – accurate enough, in fact, that the County is using this file as a base for a new Countywide address and street network file.

The TIGER roads file was extracted from the Census Redistricting data available from the US Census Bureau’s Redistricting Website.  The source of the data is the TIGER FACES file (tl_2010_06037_faces.shp) which contains all of the lines that make up the Census data.  Information was extracted using the “ROADFLG” field which separates roads from other features like streams.

Full documentation of the TIGER file is available from the Shapefiles Technical Documentation Page.  Road Classification is stored in the MTFCC field – and descriptions of the various types are available from the Appendix F Link there.  Here is a link directly to Appendix F.

Please note – we have determined that the new MTFCC codes (which replace the earlier CFCC codes) do not capture secondary roads (not minor roads, but also not highways).  The County will be fixing this as we move forward.

Download the data

• Zipped shapefile: Tigerroads.zip

Samples

These are very schematic thumbnails.