Burt's solar compass for surveying was invented out of need for a compass that was not affected by large iron deposits in a land district. He first encountered in Michigan the problem of the needle in a normal magnetic compass fluctuating erratically in all directions. This interference of course didn't allow surveying of the area. This was due to a large deposit of iron ore in Marquette County, Michigan. It turned out to ultimately be the Marquette Iron Range and mining towns sprung up in the county to get the iron ore.