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?
Where do I obtain GIS products and services?
What are the hours of operation?
What products are available for purchase?
What are the available data formats?
Where can I get more information about available data?
What services are available?
What are custom maps?
What are custom reports?
What is analytical analysis?
How is the data divided up into tiles?
How can I determine where my area of interest is according to the tiling structure?
How long does it take to complete an order?
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?
Why does the application take so long to load?
Why do the maps print on two pages?
Can I print the map to a particular scale?
How do I stop the measure tool?
How do I erase the line created by the measure tool?
How do I remove the yellow on the selected area?
Why is the point for my address not on my building?
Why are there different grids in Baltimore County?
Is data available on the key sheet grid or positions sheet grids?
What does the label for the ADC Index mean?
What does the label for the VARGIS Tiles mean?
What is a Community Crime Profile?
What size is the circle that buffers around the address selection?
How was the size of the circle established?
How is the extent of the selected area determined (displayed in yellow)?
Why does the size and shape of each selected area vary (displayed in yellow)?
Where do the statistics in the community crime profile report come from?
How often are the statistics updated?
Are more detailed statistics available for an area?
How can I obtain more detailed statistics for an area?
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 Cost Benefit Study .
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.
Back To Geographic Information Systems
Q. Where do I obtain GIS products and services?
A. GIS products and services are available in the Office of Information Technology, GIS Lab. The GIS lab is located in Room 50 of the Old Court House.
Q. What are the hours of operation?
A. The GIS Office is open Monday thru Friday, 8:30 am to 4:30 pm, except on holiday closings.
Q. What products are available for purchase?
A. Products include map data, attribute (descriptive information about map features) data and published maps. The County's base map data and most thematic data are available for purchase.
Q. What are the available data formats?
A. Map data is available in computer-aided drafting and design (CADD) export format (.dxf), shapefiles (.shp), and ArcGIS export (.e00). Images are available in tag image format (.tif) and MrSID compression (.sid) formats.
Q. Where can I get more information about available data?
A. Data about the data, commonly referred to as metadata, is available from the Descriptions page. The Descriptions page has abstracts on each data layer listed (Federal Geographic Data committee (FGDC) compliant metadata).
Q. What services are available?
A. GIS services include production of custom maps, custom reports and analytical analysis. In addition to paying for the products involved in producing the custom product, $25 per hour is charged for developing a customized product.
Q. What are custom maps?
A. Custom maps generally involve combining several map themes in a single product. An example would be to combine property lines with an orthophotograph.
Q. What are custom reports?
A. Custom reports are generated from existing attribute databases. The requestor specifies the content and format.
Q. What is analytical analysis?
A. Analytical analysis involves performing spatial analysis to develop new information. An example would be overlaying zoning and parcel data to get an estimate of development potential.
Q. How is the data divided up into tiles?
A. The County uses two standard grids, 200 scale and 600 scale. The 200 scale grid is 6,000 feet by 4,000 feet. The 600 scale grid is 18,000 feet by 12,000 feet.
Q. How can I determine where my area of interest is according to the tiling structure?
A. The FindTile application is available to assist internet user's to locate the tiles in their area of interest. Walk-in customers can use index grids available in the GIS Lab.
Q. How long does it take to complete an order?
A. Orders are generally available 24 hours after the request is received. Customers with orders requiring additional time will be contacted in advance by phone or e-mail.
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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 1995, 1996 and 1997. 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 2005. 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:
Douglas M. Adams, Business Analyst - GIS & Imaging
dadams@baltimorecountymd.gov
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Q. Why does the application take so long to load?
A. The application you are accessing requires a significant amount of time to initialize. This application is accessing county-wide map and image databases. The amount of time will vary depending on your internet connection.
Q. Why do the maps print on two pages?
A. Maps usually print on two pages because your printer is not properly setup. Refer to the Tips Section under Interactive Maps for the proper settings.
Q. Can I print the map to a particular scale?
A. No, the application does not support printing to particular scales. The print function scales the information from on your screen to fit on the paper with the marginal information.
Q. How do I stop the measure tool?
A. Double-click the left mouse button. Make sure your browser is ready to accept new input before performing the operation.
Q. How do I erase the line created by the measure tool?
A. Click the clear selection tool.
Q. How do I remove the yellow on the selected area?
A. Use the clear selection tool.
Q. Why is the point for my address not on my building?
A. The address entered into the application is computed using an address range. Address ranges are assigned to road segments not to individual buildings, therefore, the point generated by the system to indicate the address will not be on the desired building.
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Q. Why are there different grids in Baltimore County?
A. Grids are established based on coordinate systems and published map scales. Baltimore County originally used the Baltimore County Metropolitan Grid System but recently switched to the Maryland Coordinate System.
Q. Is data available on the key sheet grid or positions sheet grids?
A. Digital data is not available tiled on either the key sheet or position sheet grids. Paper maps showing utilities information are available from the Department of Public Works.
Q. What does the label for the ADC Index mean?
A. The label in the ADC Index refers to the map page and grid reference. For example, 26E4 indicates map page 26, grid E4.
Q. What does the label for the VARGIS Tiles mean?
A. The label is the name associated to the grid tile. Refer to the VARGIS metadata for more information.
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Q. What is a Community Crime Profile?
A. The Community Crime Profile is an internet map service (IMS) application designed to provide summary crime statistics for an area encompassing a radius of 1/2 mile from a given location of interest. The "location of interest" can be an address, intersection or a geographic area defined by the user.
Q. What size is the circle that buffers around the address selection?
A. The circle for address and intersection selections is defined by a 1/2 mile and appears as a red circle.
Q. How was the size of the circle established?
A. The radius is somewhat arbitrary. System testing suggested that reporting areas generally included within a 1/2 mile of a "location of interest" accurately defined communities located within urbanized areas. A radius less than or greater than 1/2 mile either returned too little or too much information that made it difficult for a user to visualize or understand. It is believed that the area included within a 1/2 mile radius reflected the surrounding environment that may, in turn, influence crime.
Q. How is the extent of the selected area determined (displayed in yellow)?
A. The selected area (displayed in yellow) is determined by intersecting the circle buffer with the police reporting areas. Any police reporting area intersecting the selection will be included in the summary crime statistics table. Since the size and shape of reporting areas vary the size and shape of the selected area will also vary. Within the 1/2 mile area around a "location of interest", the number of selected reporting areas that intersect the area will be included.
Q. Why does the size and shape of each selected area vary (displayed in yellow)?
A. The size and shape of the selected area varies because police reporting areas are the statistical unit used for reporting crime in the county. Baltimore County has been subdivided into over 1,500 reporting areas. Reporting areas based on land use, community associations, recorded subdivision boundaries and natural barriers such as streams or lakes. A reporting area represents the smallest geographic unit used by police. Within the 1/2 mile area around a "location of interest", the number of selected reporting areas that intersect the area will be included.
Q. Where do the statistics in the community crime profile report come from?
A. Summary crime statistics are reported by Baltimore County Police to the FBI in accordance with Uniform Crime Reporting (UCR) guidelines. Uniform Crime Report statistics are derived from information contained on offense and arrest reports. Federal guidelines are used to define the types of crimes reported by local law enforcement agencies to the FBI.
Q. How often are the statistics updated?
A. Crime statistics shown in the Community Crime Profile Summary Statistics table are updated every three months. The statistics reported in the Community Crime Profile table are generally six months behind the current date.
Q. Are more detailed statistics available for an area?
A. Yes, detailed information required by the FBI's Uniform Crime Report is also available for offense and arrest reports completed by police.
Q. How can I obtain more detailed statistics for an area?
A. The public can obtain information on current crime problems by calling the Police Department's Crime Information Hotline at 410-583-2309 and pressing the #4 key on a touch-tone phone. The Crime Information Hotline also contains summary statistics by community and zip code, as well as information on crime prevention. Crime statistics for a specific area can be obtained by sending a written request to:
Baltimore County Police Department
Analysis Unit
700 East Joppa Road
Towson, Maryland 21286-5501.
Be sure to clearly identify the area of interest and the reason for your request.
Back To Community Crime Report
Revised December 5, 2008
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