. during the year ended december 31 , 2003 , the company sold approximately 300 non-core towers and certain other non-core assets and recorded impairment charges to write-down these and other non-core assets to net realizable value . as a result , the company recorded impairment charges and net losses of approximately $ 16.8 million , $ 17.7 million and $ 19.1 million for the years ended december 31 , 2005 , 2004 and 2003 , respectively