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Using rock art enhancement software to investigate hidden markings on aircraft wreckage
Daniel J. Leahy
While travelling through the Northern Territory in 2012 I visited the storage facility of the Aviation Historical Society of the Northern Territory (AHSNT) to view the wreckage of a Bristol Beaufighter that had been salvaged from its crash site some time during the 1970s or 1980s (Kane-Maguire 2011:218-219). The wreckage was believed to be that of Beaufighter A19-208 of No. 31 Squadron, RAAF, which became lost over Australia while returning from a mission over Timor on 24 September 1944 (NAA 1947). The pilot, S/Ldr Wilbur Lawrence Wackett, and his Navigator, F/O Keith Eric William Noble are still listed as missing to this day (CWGC n.f.d.).
The wreckage consisted of a large piece of the rear fuselage of a Beaufighter aircraft. From an initial look at the wreckage it appeared that there were no identifying marks to confirm that this was part of A19-208 – presumably years in the elements at the crash site (and possibly open storage) had eliminated any of the wartime markings. Upon closer inspection, the ‘ghost’ of a number “5” could be discerned (see Figure 1).
DStretch is a plugin for the ImageJ software package which is used by archaeologists and rock art researchers to bring out details of pictographs that are invisible to the naked eye. The software uses a process called ‘decorellation stretch’ on existing digital photographs and does not require special lighting to be used at the site. The process was originally developed by the Jet Propulsion Laboratory (JPL) and has also been used by NASA to enhance photographs taken by the Mars rovers (Harman 2008).
The original photo of the ‘ghost’ figure on the Beaufighter wreck (Figure 1) was loaded into the software which was then commanded to cycle through its default modifications in an effort to enhance the image of the markings. As the software cycled through its various settings it was clear that some made the markings harder to read, whereas other settings appeared to make the markings stand out (see Figure 2).
One of the clearer images produced through this process was selected (see Figure 3) as it clearly shows the figure “5” mentioned above, which is followed by a figure “6”. Another figure – possibly a “2” or an “8” – appears between these two numbers. Further to the left, appearing in a lighter shade than the numbers, very faint outlines of what could possibly be “NE” can be seen. While this does not account for the RAAF’s serial number of A19-208, the serial number assigned to the aircraft by the Royal Air Force (RAF) prior to delivery to the RAAF was NE586 (NAA 1946). This subsequently confirms that the wreckage was indeed from the Beaufighter flown by S/Ldr Wackett and F/O Noble in 1944.
These markings were applied to the aircraft soon after its manufacture during World War II and are not modern interpretations of period markings. While the identity of this particular aircraft was never in doubt, this exercise has shown that continual reassessment of pieces in museum collections, through the use of modern technologies, may return results allowing for more complete documentation of artefacts. This is particularly important in cases where museums may be intending to sandblast / repaint artefacts in the interests of display, yet in the process would be destroying the original evidence in favour of an interpretation.
Commonwealth War Graves Commission [CWGC] n.f.d. Wackett, Wilbur Lawrence. Retrieved 29 August 2017 from <http://www.cwgc.org/find-war-dead/casualty/2226719/WACKETT,%20WILBUR%20LAWRENCE>.
Harman, J. 2008 Using decorrelation stretch to enhance rock art images. DStretch. Retrieved 28 August 2017 from <http://www.dstretch.com/AlgorithmDescription.html>.
Kane-Maguire, L. 2011 Lost Without Trace: Squadron Leader Wilbur Wackett, RAAF. Canberra: Air Power Development Centre.
National Archives of Australia [NAA] 1946, Aircraft status cards - Beaufighter A19-1 to A19-218, A10297, BLOCK 106.
National Archives of Australia [NAA] 1947, NOBLE, Keith Eric William - (Flying Officer); Service Number - 424052; File type - Casualty - Repatriation; Aircraft - Beaufighter A19-192; Place - Kalpalga Station, Northern Territory; Date - 24 September 1944, A705, 166/30/81.
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