Airborne Electromagnetic (AEM) Survey

​Who is involved? Helicopter towing electromagnetic instrument

The U.S. Geological S​urvey (USGS) is conducting this scientific research project in partnership with the following:

  • Wisconsin Department of Agricultural, Trade and Consumer Protection (DATCP)
  • Wisconsin Department of Natural Resources (DNR)
  • Wisconsin Geological and Natural History Survey (WGNHS) 

What is the survey?

The survey will use airborne electromagnetic (AEM) technology to update depth to bedrock maps for areas in northeastern Wisconsin. The data will provide a depth to Silurian/Karst bedrock contours that update existing map information. The use of a helicopter-towed AEM sensor (looks like a large hoop hanging from a cable) for this type of evaluation is new and provides accurate science-based data about below ground properties that are otherwise difficult to assess over large areas. This project is in response to public feedback on groundwater quality, limited data on depth to bedrock, and to further define aquifer properties in relation to surface activities.

When and where will it happen?

Flights are expected to start in early January 2021 and exact dates will be weather dependent. At this time, surveying will take place in the following counties: Brown, Calumet, Door, Fond du Lac, Kewaunee, Manitowoc, and Sheboygan.

Why is measuring the depth to bedrock important for water quality?

The project is a result of the technical standard to support implementation of Wis. Admin. Code NR 151.075 - Silurian bedrock performance standards​. The technical standard identifies science-based methods for measuring depth to bedrock and serves as a resource for landowners who mechanically apply manure to cropland. Under NR 151.075, you cannot apply manure mechanically to cropland where the depth to Silurian bedrock is two feet or less and other restrictions apply for depths 20-feet or less. Because Silurian is a type of bedrock that allows materials to pass through it more easily, this rule and technical standard work together to help prevent potential pathogens (disease causing organism) from reaching groundwater.

How does this help you?

This survey supports public health efforts to help protect groundwater from potential pathogens and promote water quality. The results of the survey will:

  • Reduce the financial burden on private landowners to verify existing maps
  • Create a better understanding of aquifer properties
  • Address groundwater quality
  • Decrease mechanical manure applications in very shallow depth to bedrock areas

This project uses the strength of local, state, and federal resources to help many citizens in the northeastern part of the state.

Helicopter Activity: What to Expect

Map of where the helicopter will be flying:

Map of northeast Wisconsin that highlights the surveying area the helicopter will fly over

  • Flights are expected to take 7-10 days depending on weather and flight conditions
  • The helicopter is flying a grid with 1/2-mile spacing, so it will be seen several times in the same area 
  • The helicopter will not fly within 500​ ft of buildings according to Federal Aviation Administration (FAA) rules, and will make efforts to fly around people or large equipment on the ground
  • The electromagnetic device will not harm plants, animals, or humans
  • The low flying helicopter may startle wildlife and cattle and the helicopter will make efforts to fly around confined animal areas
  • Local enforcement and conservation contacts are informed of the activity
  • A flight trac​ker will map the daily progress of the study
  • Only depth to bedrock and aquifer properties will be identified through this process 

Additional Information

General footage of the surveying equipment: ​

Example of how to view and use the data:


This project is a multi-agency partnership. Contact the appropriate area below based on the topic of your question.​





​NR 151 or associated compliance requirements


​Joe Baeten

​(920) 366-2072

​Verification of depth to bedrock standard


​Rachel Rushmann
Jennifer Heaton-Amrhein

​(608) 590-7357
(608) 577-8595

​AEM survey and flight paths


​Matt Komiskey
Burke Minsley

​(608) 235-0621​
(303) 236-5718

​Calibration line for the AEM survey


​Dave Hart

​(608) 262-2307​