Aeromagnetic Anomaly Mapping for Navigation.

Generating magnetic anomaly maps for use with MagNav (magnetic anomaly navigation) is a challenging problem. Current aeromagnetic survey design requirements, procedures, and processing software are often proprietary and specifically designed for geological interpretation. This article introduces a detailed aeromagnetic anomaly survey process and open-source Python software library to easily generate a MagNav map based on a single, given survey. This process and software library was used for generating maps of four overlapping surveys at Camp Atterbury (Edinburgh, Indiana). We used a fixed-wing unmanned aerial vehicle (UAV) modified for magnetic surveyance and local ground magnetic reference station for these surveys. The correlation between the overlapping portions of the final survey maps were then calculated and analyzed to evaluate map accuracy and repeatability. Across the four surveys measured and processed, two surveys were well made-made and repeatable with correlation coefficients up to 0.81. One survey suffered from aircraft calibration issues. Additionally, we developed a novel method to estimate local magnetic temporal variations. This method may remove the need for a local magnetic reference station during aeromagnetic surveys. Using this method, extended reference station modeling (ERSM), we show that temporal variations in the local magnetic field can be estimated accurately using a magnetic observatory up to 2400km away. Testing the ERSM method with data from International Real-time Magnetic Observatory Network (INTERMAGNET) magnetic observatories resulted in root mean square errors (RMSE) and error standard deviations as small as 3.64 nT and 3.24 nT, respectively, when estimating local temporal variations.