Greater Des Moines homeowners gained some ground in the third quarter on the value of their homes, according to a report from real estate analytics firm CoreLogic Inc. A little less than 7,500, or 6 percent, of residential properties with a mortgage were in negative equity during the quarter, according to the report. That number is down from 8,783, or 7.4 percent, at the same time last year. Negative equity means that homeowners owe more on their mortgages than the value of their residences. Nationally, 256,000 properties regained equity in the third quarter, meaning that 92 percent of homeowners had equity in their properties.