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Frequently Asked Questions

Geographic Information Systems (GIS)

What is a geographic information system (GIS)?
What kind of data is used in a GIS?
What is spatial data?
What is attribute data?
What is the value of linking spatial and attribute data?
How does Baltimore County use GIS?
What data is available to the public?

Map Data

Why is my house not shown on the buildings layer?
How often will the buildings be updated?
Why is my house not on the photograph?
How often will the photograph be updated?
How do I report discrepancies in the data?

Geographic Information Systems

Q. What is a geographic information system (GIS)?

A. GIS is a tool that displays and analyzes map themes to obtain more information about a feature.

Q. What kind of data is used in a GIS?

A. GIS uses two types of data: spatial and attribute.

Q. What is spatial data?

A. Simply put, spatial data is digital maps and photographs. The data has special properties that allow the data to be viewed and analyzed on a computer. Spatial data can be further defined as vector and raster. Vector data has features made up of points, lines and polygons. Raster data is made up of pixels (picture elements). 

Q. What is attribute data?

A. Attribute data is what we know about a feature. Examples of attributes include address, name, size, value, etc. Attributes are usually stored in databases or spreadsheets. In a GIS, attributes can be linked to spatial data.

Q. What is the value of linking spatial and attribute data?

A. Linking spatial and attribute data allows the user to analyze the relationships between the location of features and their attributes. For example, you can find all of the buildings within one mile of a location that are over 50,000 square feet in size.

Q. How does Baltimore County use GIS?

A. Baltimore County agencies use GIS for a variety of applications. GIS is used in Planning, Public Safety, Environmental Protection, Infrastructure Management and numerous other applications. For more information, follow the link to the GIS Strategic Business Plan.

Q. What data is available to the public?

A. Most GIS data produced by the county is available to the public. The only data that is not available is data with restricted access, such as protected by the Privacy Act.

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Map Data

Q. Why is my house not shown on the buildings layer?

A. The buildings layer is part of the County's planimetric/topographic database that was compiled from aerial photography dated 2005. Click on the aerial photography link for a graphic that shows a general overview of what areas where compiled when.

Q. How often will the buildings be updated?

A. The buildings will be updated periodically based on the database maintenance schedule. Refer to the Data Section under Resources for announcements of new data.

Q. Why is my house not on the photograph?

A. The photograph is from imagery acquired in the spring of 2008. Changes to the landscape after that date will not be on the photography.

Q. How often will the photograph be updated?

A. The photograph will be updated periodically. Refer to the Data Section under Resources for announcements of new data.

Q. How do I report discrepancies in the data?

A. Information about Data Discrepancies can be forwarded to the Office of Information Technology, Business Application Unit/GIS. Send comments to: gis@baltimorecountymd.gov.

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Revised September 27, 2013

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