Photo analysis by Bruce Maccabee July 19, 2010
July 7, 2010, at about 8 PM (standard time; about an hour after sunset), the presence of a "UFO" over the major airport in Hangzhou, China (approximate latitude 30.2 deg, longitude 120.2 degrees), caused the airport to be temporarily shut down. This event eventually made international news. Photos of an object were taken from (at least) four locations in the city. The press reports of the airport shutdown typically included one or more of four photos and thus implied that the photo(s) showed the object that caused the airport shutdown. As of this writing there is no clear evidence available to civilian researchers that proves the depicted object was the one that caused the airport shutdown. Instead, the available evidence indicates that the photos are unrelated to the airport shutdown. The question then is, what sort of object was photographed? The analysis of the photos is the subject of this article. Here are the photos in no preferred order. The locations of the photographers relative to the airport are not known to this author. .............................................................




.................................................................. Each photo shows a "UFO", that is an extended bright line in the sky with some other features such as a parallel red line, "dot" images above the bright line, and, in photos 1,3 and 4, evident but "filmy" or "translucent" blue-white light bands below the bright streaks. Photo 2 has what appears to be a white beam extending from the left end of the bright elongated image. The brightness of the ground scene in each photo, considering that they were taken in the evening when outdoor lights and streetlights were on, indicates that these were not "quick" exposures such as one has for a well illuminated scene. By this I mean that, whereas a typical well lit picture would be taken using an exposure of 1/50 second or less, the exposure times for these photos could be as long as a half second or more. Objects in motion create images that are elongated or stretched in the direction of motion (this occurs when the camera is stationary during the exposure; if the camera rotates and the pointing direction changes, all images are elongated or smeared in the (opposite) direction of the rotation). Ordinarily this stretching or smear is very small with exposure times such as 1/50 sec or less unless the object is moving very rapidly. However, even a slowly moving objectcan create an elongated image when the exposure time is long such as 1 second or more. As a result of studying the image characteristics in each photo I suggest that the image in these pictures is a helicopter with a headlight, a flashing beacon, a red "running light" at its left side and a high intensity searchlight that was pointed into several different downward directions during the exposure time. The reason I suspect a helicopter is because helicopters used in law enforcement often have powerful searchlights for illuminating the ground. These searchlights are very bright and tend toward the blue end of the spectrum as opposed to, for example, sodium vapor lights that tend toward the yellow/orange(red) end of the visual spectrum. The length of the bright line is not a measure of the size of the helicopter but rather a measure of the distance traveled during the exposure time if the camera did not move or rotate. If the camera did move the length is a measure of the combined motion of the object and rotation of the camera pointing direction (a rotation of the axis of the camera lens). The dot images are not elongated noticeably because the very brief beacon flash "stops" the motion of the image on the focal plane just as a very short exposure time (short "shutter" time) or a flash picture "stops" the object motion or the camera motion (rotation). (It is the movement of an image on the focal plane during the exposure time that creates an elongated or stretched image.)


For comparison with the above pictures, consider a photo taken by a government webcam in Arlington, Virginia, during the early morning of February 10, 2005. (http://www2.nature.nps.gov/air/WebCams/parks/nacccam/wash.jpg provides the most recent such photo.) The camera looks eastward toward Washington, DC, the Lincoln Memorial and the Nation's Capitol, from a location near Arlington Cemetery. The camera automatically takes a picture periodically. (I checked on the camera for this analysis and found that it takes a picture about every 15 minutes.) It also automatically changes the exposure time in order to compensate for varying light levels (daylight to nighttime) in order to optimize the overall picture quality. At night the exposures are relatively long and the exposure time shrinks as daylight approaches. The picture below, without the textual material at the left and below, was posted on the internet with a request for explanation. As you can see from the message below (from Casey Rea), the initial thought was that it might be a UFO over Washington, DC so the National UFO Reporting Center was contacted for an opinion.
........................................................................................ (information posted by Casey Rea at "inteldesk" at 2005-02-13 22:54:42

FEB 10, 2005 03:14 EST UFO sighted over Washington DC While doing maintenace on the inteldesk.com website, I noticed something odd about the Washington image feed, and queried further. Some screen shots were taken A telephone call was placed to NUFORC.org. Hotline 206-722-3000 . The call was answered by the Director. Instructions were given to email the link, so that the image could be confirmed coming from the government webcam. located at http://www2.nature.nps.gov/air/WebCams/parks/nacccam/wash.jpg Date: 2/10/2005 00:43:53 -0800 From: "National UFO Reporting Center" To: "Casey Rea" Subject: RE: ufo over washington > Dear Mr. Rea, > > Thank you very much for the telephone call, and for the link. > > That is an unusual object! However, it might take a great deal of > investigation to prove that it is an alien ship. One possibility I believe > we have to allow for is a military aircraft with bright lights. However, > that seems quite unlikely to me, given that the airspace above the capital > is closed to most a/c. > > I will ponder the situation... > > Thanks, again, for sharing the information with our Center! > > Cordially, > > Peter Davenport .............................................................................

Subsequently the photo (without any text) was widely circulated on the internet and explanations were solicited. I was contacted and asked my opinion. Since it was a nighttime photo I assumed that the exposure was longer than usual, but no technical information on the webcam was offered so I was not provided with the exposure time. The image of interest, the bright line in the sky with dots, did appear strange, but I guessed that an aircraft with a light could have made such an image if the exposure were "long" (longer than 1/50 sec for example). While studying the photo my attention was drawn to the three elongated bright images that appear below the image of the Potomac River (and the lights that were reflected in the water). Being familiar with the area, having lived there many years ago, I knew that the probable sources of these bright lines were the headlights of cars traveling along the George Washington Parkway that runs along the south side of the river. I knew that cars traveling along this 4-lane highway typically travel at 50 - 60 mph and perhaps faster when there is little traffic (at about 3 AM). I guessed that I could use this information to estimate the exposure time if I could determine the distance from the camera to the cars on the Parkway. I obtained a map and estimated the distance from the webcam (near the Carillon) to the highway (2270 ft). Using an estimated scale factor for the photo, the number of degrees of Field of View (FOV, 35 degrees), I estimated the angular length of the elongated images made by the car headlights to be about 2.3 degrees or about 0.04 radians. Since the cars were traveling along a highway that was (at that location) approximately perpendicular to the line of sight to the cars, I multiplied the angular distance by the distance from the camera to the highway to obtain an estimate of the actual distance, D, a car traveled during the exposure time: D = 2270 x 0.04 radians = 91 ft. I did this because I knew that I could divide the distance traveled by the estimated speed, S, to get an estimate of the exposure time, Te: Te = D/S. I assumed D = 60 mph = 88 ft/second so Te = (91 ft/88 ft/sec) which is essentially 1 second. This was approximate because the actual speed was not known and the distance traveled was not exactly perpendicular to the line of sight. After reaching this conclusion I wrote the text at the left of and below the webcam photo and Casey Rea posted it on the internet. An airplane traveling faster than an automobile would travel even farther during the exposure time and make a longer line of light if it were at the same distance as the car. (The length of the elongated image of the light (bright line "UFO")in the picture depends upon the distance it traveled, the distance of the light from the camera and the angle between the actual track of the light in 3-D space as compared to the line of sight; here it is assumed that the flight track was straight and perpendicular to the line of sight from the camera). If the unknown aircraft was over the Potomac River in the "noise reduction" flight track from Reagan International Airport (RIA) then it was not much farther away than the cars and, in this case would have been traveling about three times faster. The webcam photo below taken at about 13:32 hours (1:32 PM, EDT, July 19, 2010) shows what an airliner looks like as it approaches RIA. (Note: a jet such as this is within the FOV of the camera for only seconds...a lucky photo.)

Note that the airplane image is quite distinct (very little image stretch caused by motion)because the daytime exposure time was very short (probably considerably less than 1/100 sec) .............................................................. RETURNING to the recent Chinese photos, one immediately sees the similarity as far as the headlights of an aircraft and the dot images are concerned. Photo 1 is very yellow, suggesting that sodium vapor lamps were in use to light the streets. There appears to be a mesh of some sort supported by posts. Could this photo have been taken at a ballpark? If so that could explain why there was so much light (stadium lights?) There seem to be clouds in the sky lit from below by the city lights. The "UFO" image is mostly a continuous bright line with a reddish "protrusion" at the right end. This might be a taillight indicating that the helicopter was moving right to left. There also appears to be multiple beams coming down. More likely, there was one beam that was projected downward from a series of locations as the presumed helicopter traveled. The extreme brightness that is indicated by the considerable amount of image overexposure could be a result of, not only a headlight, but also a direct view, but from the side, of the searchlight bulb. The beam traveling down toward the ground is visible only because of dust and particulate matter in the atmosphere that scatters the light out of the main beam. Since I first posted this a correspondent has sent me a URL that identifies this photo. It has nothing to do with the Hangzhou sighting! See http://commons.wikimedia.org/wiki/File:Lille_helicopter_Img004510.ppm.jpg Photo 2 is notable for the bright line "UFO" with double dot images and what appears to be a white beam of light at the left end. This photo is also notable for the (presumably accidental) "double exposure" effect. This is actually a form of image smear due to rotation of the camera sighting line during the exposure, but in this case one imagines that the camera spent a very small fraction of the exposure time, say 1/4 of the exposure time or less, pointing in an initial direction and then was very quickly rotated a small amount to a new pointing direction at which it spent the rest of the exposure time. Thus one sees a faint image of the top of the building at the left and a bit to the left of that a good image of the building. The same is true for the overhead wires and the building at the right. The image of the "UFO" is basically like the image in photo 1: an overexposed line of light. This photo also clearly shows pairs of light dots (beacon flashes). The uneven spacing could be a result of the quick camera rotation mentioned above. Again the extreme overexposure could have been a result of a direct view of bright lights on the aircraft. The light beam image at the left end of the bright streak might be an image of atmospherically scattered light from the headlights of an ordinary aircraft or from a searchlight beam that was pointed forward with the aircraft traveling right to left. In this case if there was a spotlight it was pointed forward during the whole exposure time as there is no indication of the beam pointing downward during the exposure time. Also, in this case the red running light on the left side of the helicopter (left side when facing forward in the helicopter) made a distinct image. Photo 3 shows, one presumes, the same helicopter over the city lights, however, in this case the distance to the camera is greater and so fewer details are visible. Photo 4 shows another view of (one presumes) the same helicopter. The cluster of light dots above the bright line suggests that the beacon would send out a burst of flashes and then wait for a time before another burst. As in the first photo, there is a reddish light that extends beyond the bright line. If this is a taillight then the helicopter was traveling right to left. As for the spotlight beam, it appears to have been directed toward a particular area on the ground as the helicopter flew along, thus making the beam cross itself as if focusing had occurred. The curve of the line suggests that the helicopter, while maintaining a constant altitude, changed its flight direction slightly during the exposure. It could have been a turn to the left if it was traveling left to right.


The analysis of all four photographs shows that the images are consistent with being the result of taking nighttime, "long" exposure photographs of a helicopter with a searchlight (a police helicopter presumably chasing someone). This would have nothing to do with a "UFO" shutting down an airport (unless there were a police helicopter chase through the restricted airspace near the airport.) One might wonder, then, how these photos got associated with the airport "UFO." My guess it that several people saw the helicopter and did not realize what it was. Possibly police helicopters with searchlight beams are not commonly seen in Hangzhou. Anyway, if one presumes that the photographers did not know what they photographed and then learned through news media stories about the airport "UFO", each photographer might have thought to him/herself, "Maybe I photographed that UFO." Then each photographer would take his/her picture to a newspaper or simply post it on the web. The "UFO" image in each photo does not look like a helicopter, so it would be treated as an unknown, perhaps, the airport unknown. This, in my estimation, is a possible explanation for how these "UFO" photos came about and why they were associated with the airport "UFO". As for what caused the airport to shut down, it may have been a "military vehicle" as suggested by recent stories or something else. We don't have a description of what the pilots or air traffic controllers saw, if anything, nor do we have any information regarding radar detections. We may never know. NOTE: an excellent discussion of the provenance and analysis of the above photos is presented by Kentaro Mori at http://tinyurl.com/2e7ssvk