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Census Geography 2000 - TLG Aligned; Blocks, Block Groups & Tracts

This page last updated: 08/16/2002
Metadata created using Minnesota Geographic Metadata Guidelines


Metadata Summary

Originator Metropolitan Council and The Lawrence Group (TLG)
Abstract The Lawrence Group, under contract with Metropolitan Council, created a 2000 Census Bureau block polygon dataset for the Twin Cities Metropolitan Area (Anoka, Carver, Dakota, Hennepin, Ramsey, Scott and Washington Counties). This dataset is coincident with and developed using the TLG Street Centerline and Landmarks databases where 2000 block boundaries fall on those features. For those block boundaries that are defined by features not included in TLG databases, TLG used other digital resources to generate these boundaries, such as orthophotography or additional features from city and county GIS databases. TLG used it's best judgement to digitize block boundaries when the block boundaries followed nonvisible features or street extensions

This is a MetroGIS Regionally Endorsed dataset. (See http://www.metrogis.org/data/about/index.shtml#whatis for more information.)
Browse Graphic View a sample of the data.
Time Period of Content Date 2000
Currentness Reference 2000 Census. Adjustment 7/22/2002.
Access Constraints None
Use Constraints By acceptance of this data, the user agrees to include a copy of this metadata record, including the liability disclaimer, whenever the user transmits or provides the GIS Data (or any portion of it) to another user.

We recommend that other interested parties download this dataset from the Data Finder web site (www.datafinder.org) to ensure that the most current data is obtained.
Distributor Organization Metropolitan Council
Ordering Instructions This dataset is distributed on the internet by clicking below after 'Online Linkage'. Doing so will tell your browser to download a 'ZIP' file which will contain the following:

- ArcView shape files
- metadata for the dataset (.htm)
- NOTICE.RTF, an important notice about this dataset that can be read by any word processing software.

This dataset can also be viewed and downloaded from the MetroGIS DataFinder Cafe at http://www.datafinder.org/cafe/ . The Cafe allows users to subset or clip datasets using an existing feature, such as a city or school district boundary or an ad-hoc, user defined area.

Additionally, this dataset is available for direct use via one or more map services. More information about what a web mapping service is can be found at http://www.datafinder.org/services/ . The specific map service and layer name for this dataset can be found by clicking the blue or green boxes under the map service column of the DataFinder Catalog at http://www.datafinder.org/catalog/ .
Online Linkage Click here to download data. (See Ordering Instructions above for details.) By clicking here, you agree to the notice in "Distribution Liability" in Section 6 of this metadata.

Full Metadata

Census Geography 2000 - TLG Aligned; Blocks, Block Groups & Tracts

Go to Section:
1. Identification Information
2. Data Quality Information
3. Spatial Data Organization Information
4. Spatial Reference Information
5. Entity and Attribute Information
6. Distribution Information
7. Metadata Reference Information

 
Section 1 Identification Information   Top of page
Originator Metropolitan Council and The Lawrence Group (TLG)
Title Census Geography 2000 - TLG Aligned; Blocks, Block Groups & Tracts
Abstract The Lawrence Group, under contract with Metropolitan Council, created a 2000 Census Bureau block polygon dataset for the Twin Cities Metropolitan Area (Anoka, Carver, Dakota, Hennepin, Ramsey, Scott and Washington Counties). This dataset is coincident with and developed using the TLG Street Centerline and Landmarks databases where 2000 block boundaries fall on those features. For those block boundaries that are defined by features not included in TLG databases, TLG used other digital resources to generate these boundaries, such as orthophotography or additional features from city and county GIS databases. TLG used it's best judgement to digitize block boundaries when the block boundaries followed nonvisible features or street extensions

This is a MetroGIS Regionally Endorsed dataset. (See http://www.metrogis.org/data/about/index.shtml#whatis for more information.)
Purpose The dataset was developed to have a 2000 census block database that is aligned to the TLG street centerlines and landmarks files, for use in analysis which utilizes both the census data and TLG street centerlines/landmarks. Blockgroup and tract datasets have been desolved from the block dataset. Additionally, since TLG's street centerline dataset is aligned within county rights-of-way for these counties, this dataset allows for parcel based analysis as it may pertain to census blocks, block groups and tracts.

This dataset was developed for use in a variety of GIS applications like redistricting or census data analysis.
Time Period of Content Date 2000
Currentness Reference 2000 Census. Adjustment 7/22/2002.
Progress Complete
Maintenance and Update Frequency As needed
Spatial Extent of Data Twin Cities 7 County Metropolitan Area. This includes the counties of Anoka, Carver, Dakota, Hennepin, Ramsey, Scott and Washington in Minnesota.
Bounding Coordinates -94.012
-92.732
45.415
44.471
Place Keywords Twin Cities, Anoka County, Carver County, Dakota County, Hennepin County, Ramsey County, Scott County, Washington County
Theme Keywords census, demographics, TIGER, blocks, block, block groups, block group, tracts, tract
Theme Keyword Thesaurus None
Access Constraints None
Use Constraints By acceptance of this data, the user agrees to include a copy of this metadata record, including the liability disclaimer, whenever the user transmits or provides the GIS Data (or any portion of it) to another user.

We recommend that other interested parties download this dataset from the Data Finder web site (www.datafinder.org) to ensure that the most current data is obtained.
Contact Person Information Tanya Mayer, GIS Coordinator
Metropolitan Council
390 Robert Street North
St. Paul, Minnesota 55101-1805
Phone: 651.602.1604
FAX: 651.602.1674
E-mail: tanya.mayer@metc.state.mn.us
Browse Graphic View a sample of the data.
Browse Graphic File Description Sample map showing the census_2000_tlg layer.
Associated Data Sets 2000 TIGER/Line files from the Census Bureau - http://www.datafinder.org/metadata/census_2000_tiger.htm
1990 Census Geography - TLG Aligned; Blocks, Block Groups & Tracts - http://www.datafinder.org/metadata/census_1990_tlg.htm
TLG Street Centerlines - http://www.datafinder.org/metadata/tlg_roads.htm
TLG Landmarks - http://www.datafinder.org/metadata/tlg_landmarks.htm

 
Section 2 Data Quality Information Top of full metadata Top of page
Attribute Accuracy Each block has a census block number assigned to it that represents the original Census block in the TIGER/Line file. Several water blocks and a few land are not included due to differences in accuracy and geographical representation. These blocks have 0 population. Several Census blocks and a couple block groups and tracts are assigned to more than 1 polygon for this same reason. For a more detailed list see the TLG2000Miss-Dup-blks.xls file. Other than these cases, a one-to-one correspondence has been confirmed between this dataset and the 2000 census data.

For a complete description of Census Bureau block numbering, please reference the TIGER Technical Documentation (prior to 2000 TIGER) at www.census.gov/geo/www/tiger
Logical Consistency The dataset is topologically 'clean'.
Completeness Entire seven county geographic area is covered.
Horizontal Positional Accuracy The positional accuracy of the dataset has not been tested under the National Standards for Spatial Data Accuracy.
Vertical Positional Accuracy Not applicable
Lineage Sources used in the development of the data include TLG GBF street centerlines, TLG lines of interest, TLG Areas of interest; and Metropolitan Council provided municipal boundaries and parcel based school district boundaries.

Datasets used as reference include 2000 Census TIGER/Line files, 1990 TLG Census blocks, licensed Metropolitan Council 2000 Digital Orthophotography for the seven county metro area, and licensed county parcel data.

The Lawrence Group aligned Census Blocks to their street centerline file. When Census block boundaries were not streets but MCD boundaries, they aligned them to our MCD file (available on Data Finder) and if they were school district boundaries they followed the SD boundaries we dissolved from the county parcel data. If the Census geography was so completely different that it affected the Census block boundary topology to follow our MCD or SD boundaries, they used the TIGER alignment. We found this to be more of an issue in other counties. They used the parcel boundaries as a guide when needed, and used the aerial photography for other visible physical features for Census block boundaries (like water features, railroads, etc.). There were also times when the TIGER Census geography was not reality at all, and if a block did not really exist and had no population assigned to it, it was not included in the file. Sometimes there were multiple polygons that create a block in reality, so there is a list of Census blocks with multiple polygons. This is important if you plan to sum up any census data based on the geography file (it would count those blocks more than once).

*** Thank you to Dakota County Survey and Land Information Department who had already aligned the 2000 census blocks to their parcel lines at the time of this project, and provided that file to the Metropolitan Council to be used in this final 7-county regional file. TLG used that file, made some changes to reflect block boundaries based on the rules defined for this project (approx 30 blocks affected), and converted it to the agreed upon project format.


LINEAGE FROM THE LAWRENCE GROUP

TIGER/Line 2000 Census Files using TLG based features -
Processing Documentation

Several macros and menus have been created to automate repetitive tasks and expedite manual processing.

<coun> is used to specify the first 4 letters of the county name

Step 1- Import TIGER files
Move all files from county directory on CD (Tiger 2000 data, 11-16-01, Met Council) to local directory
import covers and info files
separate feature classes so we know what line types delineate the blocks
Specific block boundary arc files:
· counblkarcs (all boundary arcs)
· counblkext (nonvisable extensions of an existing feature)
· counblkfence (fence lines)
· counblkinvis (invisible features)
· counblkmun (munics boundaries)
· counblkprop (property lines)
· counblkrds (roads)
· counblkprr (railroads)
· counblkschdis (schooldist)
· counblkwater (water- rivers, streams, ponds, lakes)

clip .tiff parcels into quads to allow quick drawing in AE

Step 2- Alignment of features
Edit UTM projected coverages

*To expedite the process, only adjust features that delineate a block boundary.
-speeds process and ensures that our features are geographically correct

1. Data sources
a. DOQ in both Tiff world and Mr. SID format
b. County supplied parcels
c. MCD Boundaries 2000 from Met Council
d. School district boundaries 2000, same as provided to create census boundaries
2. Covers to adjust, and source
a. Individual road centerline files to county parcels and DOQs
b. Geoareas to county parcels and DOQs
c. Linear to county parcels and DOQs
d. Munics to MCD boundaries
e. County to MCD boundaries

Step 3- Assemble TLG and Other Supplied Lines
- Project roads, linear, and Geoareas, clip these with the county boundary
- Use separated feature covers (from Step1) to select the appropriate linear, geoareas, munics and school district boundaries that make up block boundaries.
- display DOQs
- display different TIGER line types and parcels (colors pre set)
- put selected geoareas and linear arcs to individual files.

Step 4- Create block relationship files, and Calculate 2000 Block and Tract Values through a Relate
Create of block relationship files:
1. Copy and paste 1990-2000 data table from Census web page to a new .txt file.
2. Convert to .dbf file, data in columns 3, 4, 5, 10 is text, the rest is number format
3. In Excel add the following headings: ST90, CO90, CT90, BLK90, PART90, ST00, CO00, CT00, BLK00, PART00
4. Convert to info file into the COUN_census/COUN_tgr/ directory called COUN90_00

Relate created, relate called RELATE is saved in relate info file called censusrelates
Selects features through relate, calculate ALL00 = to ALL00 from 9_0relate1to1 info file
Puts features to new cover in coun_tgr directory
Projects and builds cover from SPTCMA83 to UTM

Step 5- Combining Points and Placing Them into Linear Features
(Continuation of above step)
Macro continues by selecting TLG polygon label points with one to one relationship from 1990 to 2000 (recalculated to blk00 values) and placing them with 2000 TIGER block poly label points. Also deletes 2000 points that had a one to one relationship that were pulled in from TLG 1990 points. By using TLG points from the 1990 census project (that had a one to one relationship), we are able to reduce manual point moving as the 1990 points have already been relocated to the centers of blocks in TLG data. Assembles linear features and places them into same coverage as points, so when built polygons with label points will be created.

Step 6- Moving Points to Create Proper Polygons
Bring up edit cover, backcovers, and menus for editing.
Select and copy points to make sure attributes are in each poly once it is built. Utilize back covers unique symbology for each feature type to determine TIGER's intended boundary, or to see the 1990 block if available.

Step 7- Building Polygons and Checking for Errors
Make 4 separate checks before converting covers to shapefiles for final visual checks.
- The first step checks for blocks that do not contain a point.
- Second checks for block polys present in the TIGER file, but not in the dissolved %.coun%work file.
- Third checks for tract polys present in the TIGER file, but not in the dissolved %.coun%work file
- Fourth is a check for polygons present in the dissolved %.coun%work file, but not in the TIGER file.
Finally the macro outputs nine shapefiles (see next step for names) for visual checks.

Step 8- Setup ArcView Project to Begin Visual Checks
In Arc View, bring up new project and view. Add the first 5 of the following themes and classify as follows:
· TLG block lines - single symbol, 1pt solid line
· TIGER block group lines - single symbol, 3pt dashed line
· TIGER block lines - single symbol, thin (.1) solid line, contrasting color
· Intersected polygons - unique value, classify field SAME, red fill, no outline
· TLG block group polygons - unique value, classify field blockgroup, your choice of color schemes
· TIGER block polygons (reference if necessary)
· TIGER Tract lines (reference if necessary)
· TLG block polygons (reference if necessary)
· TLG tracts as polygons (reference if necessary)

With the intrsct theme, classify the N (different blk00) blocks to RED with NO OUTLINE and the Y blocks to NO FILL and NO OUTLINE.

Step 9- Plotting Large Scale Maps for Visual Checks
Plot check maps on as large a sheet as possible so each block is visible. Some red is acceptable, but look closely to see that the red is simply alignment issue between TIGER and TLG data. If large red areas exist it could be a dissolve or incorrect point copied issue. Make tract and blockgroup checks. These should all be contiguous single polygons.

Step 10- Packaging and Sending Out
Drop and calculate items and export cover to .e00


CHALLENGES/PROBLEMS and SOLUTIONS

1) Census feature alignment to DOQs/Parcel data - Although technically outside the scope of work for this contract this phase took us much longer than expected. In most cases our roads were within the right of way, but we took this opportunity to do some fine tuning that we otherwise might not have done. Alignment of Area and Linear features to the DOQs was very helpful in making our features much closer to how they actually are; unfortunately this process was also time consuming and at times created difficulties in replicating the TIGER census blocks since there are differing levels of accuracy in the TIGER data.

2) Process of determining proper block geography - Correlating TIGER Geography with ours sometimes caused big headaches. Often times TIGER creates blocks using features that are either nonexistent, or whose locations are just incorrect. Initially these problems were very aggravating, but we were able to work through many of them with The Council and come up with solutions that would work on a systematic basis with these recurring issues.

3) Timing - We had difficulty completing the first few tiles on the specified dates due to a variety of problems including extra time spent aligning features, and an underestimation of the time it would take to complete the manual processing. A revised time schedule was worked out.

4) Complete renumbering of census blocks from 1990 by the Census Bureau- This was perhaps our biggest challenge. In having completed this project with the 1990 census geographies we felt that the project would proceed smoothly. By using the 1990 to 2000 block relationship files we were still able to utilize about 1/3 of the work we had previously done. In the cases where there was a one to one relationship between 1990 and 2000 blocks we were very successful in recreating the blocks. Had the blocks not been renumbered, the project would have run much more efficiently.



LINEAGE FROM THE METROPOLITAN COUNCIL

TLG delivered one county tile at a time. Metropolitan Council staff ran independent checks to account for all blocks, block groups and tracts. Then developed with TLG a list of any missing blocks, verifying zero population, and added to the list any blocks, block groups or tracts of more than one polygon, verifying that there were no errors in the block geography causing the multiple polygons. Council staff then visually checked each tile for block boundary errors. TLG fixed errors as needed and resent final county tiles.

After the final seven edgematched tiles were received from TLG, Metropolitan Council GIS staff created final region wide shapefiles of blocks, block groups and tracts. Using ArcTools, Council staff dissolved all county coverages to tracts and block groups. Using Workstation ArcInfo, double precision, staff APPENDED all seven county coverages for blocks, block groups and tracts and cleaned the three resulting files with a .001 meter fuzzy tolerance. Coverage were then converted to shapefiles using ArcView 3.2.
Source Scale Denominator
 
Section 3 Spatial Data Organization Information Top of full metadata Top of page
Native Data Set Environment ArcInfo Various Versions, UNIX platform
Geographic Reference for Tabular Data Census block, blockgroup and tract identifiers
Spatial Object Type Vector
Vendor Specific Object Types polygon shapes
Tiling Scheme One layer for entire seven county region.
 
Section 4 Spatial Reference Information Top of full metadata Top of page
Horizontal Coordinate Scheme UTM
Ellipsoid GRS80
Horizontal Datum NAD83
Horizontal Units Meters
Distance Resolution
UTM Zone Number 15
 
Section 5 Entity and Attribute Information Top of full metadata Top of page
Entity and Attribute Overview 
Polygon attributes: 
  
TRACT_2000.SHP 
  
AREA:       Area of the polygon in square meters 
  
CO:         3 digit FIPS and state standard county code; e.g. 163, 003 
  
TRACT:      6 digit Census Tract number  
  
  
BLKGRP_2000.SHP 
  
AREA:       Area of the polygon in square meters 
  
CO:         3 digit FIPS and state standard county code; e.g. 163, 003 
  
BLOCKGROUP: 7 digit Census Block Group number (Tract + 1st number of the block  
            code)  
  
  
BLOCK_2000.SHP 
  
AREA:       Area of the polygon in square meters 
  
BLK00:      15 digit block code includes STATE, CO, TRACT & BLOCK 
  
STATE:      2 digit FIPS standard state code; e.g. 27 
  
CO:         3 digit FIPS and state standard county code; e.g. 163, 003 
  
TRACT:      6 digit Census Tract number  
  
BLOCK:      4 character Census Block number  
  
BLOCKGROUP: 7 digit Census Block Group number (Tract + 1st number of the block  
            code)  
   
  
Field types for the above attributes are as follows: 
  
AREA:       Numeric 
  
BLK00:      String 
  
STATE:      Integer 
  
CO:         String 
  
TRACT:      Integer 
  
BLOCK:      String 
  
BLOCKGROUP: Integer
Entity and Attribute Detailed Citation http://www.census.gov/geo/www/tiger

Census 2000 TIGER/Line Technical Documentation and Metadata
 
Section 6 Distribution Information Top of full metadata Top of page
Publisher Metropolitan Council
Publication Date 08/16/2002
Contact Person Information Mark Kotz
GIS Database Administrator
Metropolitan Council
390 Robert Street North
St. Paul, Minnesota 55101-1805
Phone: 651.602.1644
FAX: 651.602.1674
E-mail: mark.kotz@metc.state.mn.us
Distributor's Data Set Identifier census_2000_tlg
Distribution Liability NOTICE: The Geographic Information System (GIS) Data to which this notice is attached are made available pursuant to the Minnesota Government Data Practices Act (Minnesota Statutes Chapter 13). THE GIS DATA ARE PROVIDED TO YOU AS IS AND WITHOUT ANY WARRANTY AS TO THEIR PERFORMANCE, MERCHANTABILITY, OR FITNESS FOR ANY PARTICULAR PURPOSE. The GIS Data were developed by the Metropolitan Council for its own internal business purposes. The Metropolitan Council does not represent or warrant that the GIS Data or the data documentation are error-free, complete, current, or accurate. You are responsible for any consequences resulting from your use of the GIS Data or your reliance on the GIS Data. You should consult the data documentation for this particular GIS Data to determine the limitations of the GIS Data and the precision with which the GIS Data may depict distance, direction, location, or other geographic features. If you transmit or provide the GIS Data (or any portion of it) to another user, the GIS Data must include a copy of this disclaimer.
Transfer Format Name ArcView Shape files
Transfer Format Version Number ArcView: 8x
Transfer Size 13 MB for ZIP file
Ordering Instructions This dataset is distributed on the internet by clicking below after 'Online Linkage'. Doing so will tell your browser to download a 'ZIP' file which will contain the following:

- ArcView shape files
- metadata for the dataset (.htm)
- NOTICE.RTF, an important notice about this dataset that can be read by any word processing software.

This dataset can also be viewed and downloaded from the MetroGIS DataFinder Cafe at http://www.datafinder.org/cafe/ . The Cafe allows users to subset or clip datasets using an existing feature, such as a city or school district boundary or an ad-hoc, user defined area.

Additionally, this dataset is available for direct use via one or more map services. More information about what a web mapping service is can be found at http://www.datafinder.org/services/ . The specific map service and layer name for this dataset can be found by clicking the blue or green boxes under the map service column of the DataFinder Catalog at http://www.datafinder.org/catalog/ .
Online Linkage Click here to download data. (See Ordering Instructions above for details.) By clicking here, you agree to the notice in "Distribution Liability" above.
 
Section 7 Metadata Reference Information Top of full metadata Top of page
Metadata Date 08/16/2002
Contact Person Information Tanya Mayer, GIS Coordinator
Metropolitan Council
390 Robert Street North
St. Paul, Minnesota 55101-1805
Phone: 651.602.1604
FAX: 651.602.1674
E-mail: tanya.mayer@metc.state.mn.us
Metadata Standard Name Minnesota Geographic Metadata Guidelines
Metadata Standard Version 1.2
Metadata Standard Online Linkage http://www.gis.state.mn.us/stds/metadata.htm

This page last updated: 08/16/2002