Pipeline Patrol flew through traffic pattern of an uncontrolled airport during period of high activity resulting in a NMAC.

Narrative

It was a sunny morning. There were at least six other aircraft in the pattern and area. As busy as it was; all pilots were doing an excellent job over the past two hours with continuous position reports. The pilots were giving good reports; local landmarks (over the lake; the freeway; the speedway; etc) distance and altitude etc. While in the pattern; I was at midfield downwind; one half mile wide pattern; when I heard the pipeline patrol pilot report '3 miles south; will cross the approach end of 30' the active runway. I made my position reports and continued the landing pattern. Other aircraft made reports and continued as well. I heard nothing further from the pipeline patrol aircraft. When I made my final approach call; I was on .5 mile final; less than 400 FT AGL and descending. At that point the pipeline pilot asked me on the radio where I was. I looked to my left and saw him on a 90 degree collision intercept over the ILS lights. I called him and said; 'I am right below you. CLIMB CLIMB CLIMB' and I continued my final approach as I was now 100 feet and over the approach. I saw his shadow go over me. Nothing more was heard from him on the radio as he departed to the north-northwest. I estimated he was less than 100 FT above me. Other CFI on the ground who witnessed it said 200 FT. For some reason I thought he was going to over fly the airport at 2;500 FT MSL (1;540 AGL) and not 300 FT AGL. TPA is 1;760 MSL; 800 AGL. I respect that the pipeline patrol pilot has a job to do. However; he could have caused a collision with his insistence on flying through the busy pattern area; over the ILS lights on final approach while there several aircraft in the pattern.