Anthony Johnson has been appointed an independent director of Essex Corp.'s board of directors. Johnson is director of the Center for Advanced Studies in Photonics Research and a professor of physics and of computer science and electrical engineering at the University of Maryland, Baltimore County. He succeeds Frank Manning, founder of Essex, who has retired from the board. Manning will retain his position as chairman emeritus of Essex, a Columbia, Md., provider of optoelectronic and signal processing services and products for intelligence, defense and communications markets.   . . .   A new National Institute of Standards and Technology (NIST) Web site, at ats.nist.gov/VSC/jsp/, enables manufacturers to check the accuracy of measurement software used to verify the smoothness of product surfaces. NIST said the free service is particularly useful for automotive, aerospace and optic industry engineers, who rely on precise measurements of surface smoothness to ensure the efficiency of cylinder-piston engines, to make high-performance metal wind tunnels and to produce better optical components. It includes NIST 2-D surface texture analysis software and a database of surface profiles, or "silhouettes," including parameters calculated by NIST. Visitors can download profiles from the site and run them with their own measurement software, or they can upload their own profiles and run the data through the NIST analysis software. NIST, which developed the site with the University of North Carolina at Charlotte, said it expects to add 3-D topographic data and associated calculated parameters in 2005.