Introduction to the Digital BASIntroduction to the Digital BAS

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OverviewOverview

• What is the MAF/TIGER Database?

• What is included in the Digital BAS package?

• What is the difference between Digital BAS and MTPS?

• What are some tips for updating the BAS materials digitally?

• How do I return my digital submission to the Census Bureau?

• MTPS and Digital BAS Demo

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MAF/TIGER DatabaseMAF/TIGER Database

• Master Address File/Topologically Integrated Geographic Encoding and Referencing (MAF/TIGER Database)

• Rather than having one layer for each feature class, all information is stored in a single layer

• Database is constructed of nodes, edges, and faces

• Each edge can represent the boundary for multiple geographies:– Place, County, Tract, School District, Voting District

Boundaries, etc.

• Changing a place boundary can affect boundaries for other geographies

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Census Tract

Edges

Incorporated Place

IntegratedLayer

School District

Topological RelationshipTopological Relationship

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MAF/TIGER Database - EdgesMAF/TIGER Database - Edges

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MAF/TIGER Database – County SubdivisionsMAF/TIGER Database – County Subdivisions

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MAF/TIGER Database – School DistrictsMAF/TIGER Database – School Districts

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MAF/TIGER Database – Voting DistrictsMAF/TIGER Database – Voting Districts

1. Letter and Form– Contains your username for MTPS: bas– You do not need to fill out the form when responding digitally

2. MAF/TIGER Partnership Software CD

3. Data and Respondent Guide CD/DVD– Contains shapefiles for use with Digital BAS and MTPS– Contains respondent guides for Digital BAS and MTPS

4. No Change postcard

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BAS Package MaterialsBAS Package Materials

• Participants use their own GIS to create the digital BAS submission file:– Create change polygons representing the difference

between local boundaries and the Census Bureau’s boundaries

– Attribute each polygon with the required information

• We send out ESRI shapefiles (.shp), but any GIS that can read/convert shapefiles may be used

• It is important to read the Digital BAS respondent guide carefully to make sure you include all required information

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Digital BASDigital BAS

• As an alternative to another GIS software, participants may use the Census Bureau’s free MTPS to create the digital BAS submission file.

• The MTPS forces the user to include the required attribute information for the boundary and feature updates.

• The software handles the data conversion and compresses all of the output files together for you to create the final digital BAS submission file.

• MTPS is appropriate for users who are not experienced in GIS or do not have their own GIS software.

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MAF/TIGER Partnership Software - MTPSMAF/TIGER Partnership Software - MTPS

• We cannot accept a local GIS file to “replace” our existing boundary information:

– Must have legal documentation and effective dates for all legal boundary changes

– We must keep record of all changes made for reference purposes

– Topologically integrated database

• Snap to existing census geography where appropriate:

– Use existing census roads, rail, and hydro wherever possible (if our river and your river differ spatially by 10 feet, snap to our river)

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Digital Update GuidelinesDigital Update Guidelines

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• Census files are in GCS NAD 83 format and can be projected into any local coordinate/projection

• Most GIS software packages will allow users to transform file coordinate systems and projections

– In ArcGIS, use the Project tool in ArcToolbox

Data ProjectionsData Projections

1. Annexations & Deannexations

2. Boundary Corrections

3. Geographic Corridors & Offsets

4. New Incorporations

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Types of Boundary UpdatesTypes of Boundary Updates

1. Linear Features

2. Point Landmarks

3. Area Landmarks

4. Address Ranges

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Other Acceptable UpdatesOther Acceptable Updates

• These are referred to as legal boundary changes:–Large change polygons are most likely annexations–Change polygons are sometimes not contiguous with your boundaries

• A change to the entity’s boundary through a legal action:–Ordinance/Resolution–Local law or Court order–State level action

• Must always include the following in lieu of the actual legal documentation:

–Effective Date –Ordinance/Resolution Number–Acreage required for Georgia entities

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Annexations and DeannexationsAnnexations and Deannexations

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Annexations and Deannexations Annexations and Deannexations (Attribute Table)(Attribute Table)

• Must enter the following in the change polygon attribute table for each annexation/deannexation:

–Name of the affected entity–The effective date–The document/authorization number (Ex: ordinance or resolution #)

• Change type is coded A for annexation or D for deannexation

• Minor fixes to the entity boundaries due to drafting or plotting errors.

• Should follow the general shape of the current boundary.

• Are neither annexations nor deannexations, although they may be fixing the depiction of previous annexations or deannexations.

• Boundary corrections DO NOT require legal documentation.

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Boundary CorrectionsBoundary Corrections

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Boundary CorrectionsBoundary Corrections(Attribute Table)(Attribute Table)

• Must enter the name of the affected entity in the Name field

• Enter “B” in the Change Type field to designate a Boundary Correction

• In the Relate field enter the following:

–IN if the territory needs to be in the affected entity

–OUT if the territory needs to be out of the affected entity

• An area that only includes road surface and right-of-way and does not contain any structures addressed to either side of the road.

• The Census Bureau will geocode addresses based on the centerline of road.

• There are two types of geographic corridors1.) Road through unincorporated space2.) Road through incorporated space

• BAS participants should recommend the creation of a geographic corridor ONLY when this coding would result in addresses being assigned to the wrong entity.

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Geographic CorridorsGeographic Corridors

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Example: Road through an unincorporated place

In this example, the houses are in unincorporated county, while the road ROW has been annexed into an incorporated place.

Without a corridor, the housing units along this road would be included in the incorporated place.

Geographic CorridorsGeographic Corridors

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Geographic OffsetGeographic Offset• An area claimed by an entity that is only on one side of

the road and does not include any structures addressed to the right-of-way on that side of the road.

• Policy towards Geographic Offsets:– We prefer that you do not show a boundary on a front lot line.– If houses on the far side of the road should be in your

jurisdiction, please represent the boundary on the rear lot line.– If houses on the far side of the road should NOT be in your

jurisdiction, please snap the boundary to the centerline.

• An offset should be used if you must show the boundary on the front lot line.

• Using one of these techniques insures that the residential structures will be assigned to the correct geography.

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We prefer that you snap the boundary to the centerline as offsets are difficult to maintain. If offsets are not coded as such, your boundary will be snapped.

Geographic Corridors and Offsets Geographic Corridors and Offsets Incorporated PlacesIncorporated Places

A B

For all new incorporations, we need the following:1. The official name of the new incorporation

2. The name and phone number of a contact person for processing

3. A copy of the official papers of incorporation

4. The effective date

5. The mailing address

6. The name of the HEO of the new incorporation

7. The name of the BAS contact of the incorporation, if different from the HEO

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New IncorporationsNew Incorporations

• Street features can be added or edited in MTPS or ArcGIS

• These are not required unless they serve as a boundary

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Street FeaturesStreet Features

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Data DictionaryData Dictionary

• Compress your change polygon shapefile and any other edited shapefiles into a zip file

• If you are using MTPS, the software will automatically zip the required shapefiles after you are done.

• Upload the zip file onto the Census Bureau’s FTP site.–Instructions for the site are provided in the Respondent

Guides.

• The MTPS submission file can be quite large. If you are having issues uploading the file onto the FTP site, simply remove all the files that do not contain the BAS prefix in the name, and try uploading again.

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Reporting the Data to the BASReporting the Data to the BAS

Digital BAS DemonstrationDigital BAS Demonstration

ArcGISArcGIS&&

MAF/TIGER Partnership Software MAF/TIGER Partnership Software (MTPS)(MTPS)

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