Survey Control Map Service
Baltimore County provides online access to the County's geographic information system (GIS) databases. The Survey Control application is an interactive map that allows you to access specific information about Baltimore County Control points, as well as the ability to:
- Find survey controls
- Provide more information about survey controls
- Submit conditional information about survey control
Using the Application
Review the Survey Control User Guide for a tutorial on the application. You don't need to create an account to search for survey control in Baltimore County. Users are encouraged to send survey control status updates and pictures to the email address provided in the user guide.
- Pop-up blockers must be disabled for Survey Control to function properly. Refer to your browser's support on how to check and update this feature.
- High-speed internet connections are recommended for best results.
- For optimal performance, use the latest version of Chrome, Edge, Firefox and Safari.
By selecting the below button, you are agreeing to the user terms and conditions outlined below.
Terms and Conditions Summary
Baltimore County adopted the Maryland Coordinate System, North America Datum of 1983 and the North America Datum of 1988 as its standard horizontal and vertical datums starting July 1, 1999. Prior to this date the Baltimore County Metropolitan District grid system (horizontal) and Baltimore County Datum (vertical) were used for thousands of plats and surveys throughout Baltimore County.
Both systems of survey controls are being made available from this site to assist users with all surveys performed in Baltimore County. Users of this data must check the current County Code, policies and appropriate agencies to verify the correct datums to be used on current and future projects requiring Baltimore County approvals.
Warranty and Disclaimer
The user or recipient of this data understands and acknowledges this data may be inaccurate or contain errors or omissions and the user or recipient assumes full responsibility for any risks or damages resulting from, arising from or in connection with any use of or reliance upon data displayed herein. Baltimore County, Maryland does not warrant the accuracy or reliability of the data displayed herein. Baltimore County, Maryland disclaims all warranties with regard to data displayed herein, including but not limited to, all warranties, express or implied, of merchantability and fitness for any particular purpose.
Baltimore County, Maryland additionally disclaims all obligation and liability for damages, including but not limited to, actual, special, indirect, and consequential damages, attorneys' and experts' fees, and court costs incurred as a result of, arising from or in connection with the use of or reliance upon the data displayed herein.
The user or recipient hereby waives the right to file suit or make demand and forever discharges and releases Baltimore County, Maryland, its agents, employees, successors and assigns from any and all loss, liability, damage, claim, cost or expense incurred as a result of, or arising out of or in connection with the use of data displayed herein or any reliance thereon, whether caused by the acts or omissions of Baltimore County, Maryland, its agents, employees, successors or assigns, directly or indirectly.
The user or recipient of data, hereby acknowledges that Baltimore County, Maryland, its agents, employees, successors, and assigns shall not be responsible for any and all property damage or bodily injury (including serious physical injury or even death) incurred as a result of, or arising out of or in connection with the use of or reliance upon data displayed herein.
The user or recipient hereby agrees to indemnify, protect and hold harmless Baltimore County, Maryland, its officers, agents, employees, successors and assigns from and against any and all suits, demands, losses, liability, damages, claims, costs or expenses incurred by Baltimore County as a result of, or arising out of or in connection with, the user or recipients misuse or misrepresentation of this data.
The user or recipient of the data displayed herein acknowledges and agrees to attach the appropriate notation(s) from the State of Maryland, State board for Professional Land Surveyors, Local Jurisdiction, or any other agency which requires source data information to be identified on a survey.
Understanding the Data
Learn more about how to translate the data below.
Due to the differences in the ways the two systems—the old County vertical datum (BCD) and the current version (NAVD 88)—were established, as well as other factors, there is no survey grade conversion that can be applied to convert from one system to another. We have established NAVD 88 elevations on the older BCD benchmarks and found differences ranging between 1.5 to 1.9 feet. Based on our observations, Baltimore County uses 1.7 feet as the approximate difference between the two systems. A benchmark with a BCD elevation of 100 feet would have an approximate NAVD 88 elevation of 98.3 feet.
Tidal levels, such as high tide, low tide, mean tide and others, are typically defined as the average of a 19-year period known as a tidal epoch. These water surface levels are unique to a particular site along the waterway and will not be constant along the entire length of a waterway. Many local, state, and national agencies have created fixed vertical (elevation) datums such as BCD, NGVD 29, and NAVD88 for use in surveying and engineering design. These fixed datums were originally based on water surface measurements at one or more tidal stations and may even use a water or tidal term (sea level datum or mean low tide) for the zero elevation of that fixed vertical datum. The fixed vertical datums are as the name implies "fixed" in time as of the date they are created with some of them created over 100 years ago. The elevations of the fixed datums are not revised or updated when every new 19-year tidal epoch is released. Some of the fixed datums do not factor in the differences in gravity and the other forces defining an equipotential surface. Any relationship with water surface or tidal level that may have existed when the datum was first established no longer exists today so there is no relationship between fixed datums and water level or tidal datums.
The relationship between geodetic vertical datum and water or tidal datum applies, but there is an exception in this situation. When working in Baltimore County, the Baltimore County Zoning Regulations, section 417 'Waterfront Construction' provides the information to answer this question. It states "... mean low tide as prescribed in the Baltimore County Design Manual..." The current version of the Baltimore County Design manual was adopted on August 2, 2010 and includes Plate SU-2 (Chart of Datums) in the Land Surveys Section. On Plate SU-2 mean low tide is set as zero datum. While the term mean low tide can be a water or tidal level, in the case of the Baltimore County Zoning Regulations, it defines mean low tide as a fixed elevation. When dealing with Baltimore County Zoning permits for waterfront construction, the mean low tide elevation is 0.0 feet as referred to in the old Baltimore County Datum elevation system.
Find an Existing County Control Near You
Look online via Survey Control, or fax/email a map showing your site to firstname.lastname@example.org and we will check our records for the appropriate data. We will fax or email the information back to you, or you can come to our office to pick-up the data. We will not read survey control data over the phone.
Find Current Continuously Operating Reference (CORS) Information
The Baltimore County CORS, known as BACO, is part of the National CORS network.
- For five-second epoch data—Visit the National Geodetic Survey CORS website and type "BACO" into the Enter Site ID box.
- For one-second data—Call 410-887-3540. The Land Survey Division maintains one second epoch data for a period of 60 days.
About County Surveyors
Baltimore County surveyors will give you a letter explaining their presence. If surveyors are from a private surveying firm, you will need to ask them directly. Baltimore County does not regulate the many surveying companies operating in the County. Baltimore County surveyors do not preform surveys for private citizens.
Submit a Complaint
The Maryland Department of Labor, Licensing and Regulation will investigate complaints and take any appropriate action.