1D frequency-domain solutions are compared against Leroi ​http://www.amirainternational.com/WEB/site.asp?section=news&page=projectpages/p223f_software

Frequency-domain closed-loop source

Above, a comparison of Lemma with Leroi for a square closed-loop source transmitting 20 Amps at 50 kHz. Both solutions are in excellent agreement (left). The difference plot shows that the two codes fall within .1% throughout, with minor differences focused near the corners of the loop. Calculations were made at the air-earth interface.

Same as the above plots, but calculations were made at 20m depth.