Hominid wrote the following....
The data coming from the radar site came in increments of .088° (1 4096th of a full circle) for azimuth and .25nm for range. If the likely errors were more than two times these values, the designers would simply have decreased the resolution of the data. There is no point in transmitting data to a precision of 1 if the data is only accurate to 8, for example. The direction center at McChord could have smoothed the data to get better accuracy.
But the coordinate data used to plot the FBI plot didn't necessarily take full advantage of the accuracy of the data the airforce had available. The data from which the plot was made was rounded to whole minutes of latitude and longitude. So the actual accuracy of the plots is ±.5 minutes of latitude and longitude. This was the source of the incorrect info about the '72 searchzone map to the effect that the accuracy was ±.5 nautical miles (should have been .5nm for N-S, but .347nm for E-W)
The positions were determined by computations, almost certainly by the airforce 84th radar evaluation squadron, using the coordinates and associated time stamps obtained from the Mt. Hebo site, plus the surveyed location of the Mt. Hebo site and the earth model of the time. The 84th had, and still has, a detachment at McChord and doing such analyses was part of their official functions and still is today. The McChord direction center just used the SAGE system in their normal function of tracking practically everything bigger than a piper or cessna. They did not analyze the system or data from it.
Shutter, if Hominid is still around how about getting him to explain where those numbers above came from?
In the 1971 time frame, radar antennas made about 6 revolutions per minute or about one revolution about ever 10 seconds. That means the radar would paint an aircraft only about ever 10 seconds and the antenna would rotate about 60 degrees in that time frame.
In that 10 seconds, an airliner with a ground speed of about 180 knots, or 3 nautical miles per minute, would travel about one-half of a nautical mile or about 3000 feet.
The numbers presented above by Hominid are nonsense. Radar used in tracking aircraft has never been that accurate in tracking aircraft or anything to my knowledge. I believe Ammerman was recently quoted as saying that his radar display was only accurate to within several miles.
The Portland radar was not involved in the actual tracking of the airliner, that was strictly up to the Seattle ATC Controllers. The operator apparently just happened to see it on his local display and he probably could not be certain that he was looking at 305 in the first place.
The SAGE system was reportedly not on line that night in the first place. And all raw radar data used by the FAA and the USAF probably came from the same radar at McChord AFB.
