People have been seeing and reporting strange and unexplainable sightings of flying objects for thousands of years. Despite these uncountable eyewitness accounts there has yet to be irrefutable proof of what these objects are or where they come from. Like a forensic scientist piecing together the clues from a crime scene, ufologists must collate many bits and pieces of information in order to more firmly establish the existence and characteristics of UFO's in order to get a closer idea of what the reality of this phenomena is.
Visual evidence is intriguing, but not always a strong element of proof. For a multitude of reasons, from attention seeking to malicious mischief, people can fabricate stories about seeing UFO's. Witness reports have to be filtered for truth. Dr. J. Allen Hynek, consultant for the United States Air Force and founder of the Center for UFO Studies insisted on two primary criteria to determine useful information about UFO sightings. Credibility of the witness was very important to him. Among the highest level of credibility are astronauts, military and civilian pilots, radar operators, and law enforcement officers; all people with much to lose by making their reports known. Strangeness, the degree of variation from the behavior patterns of known objects, was Dr. Hynek's second criteria for filtering factual information from the lies and hoaxes that also abound in UFO research.

Photographic evidence can be very strong proof of the existence of UFO's. Older emulsion-based photographic and movie film, as well as video tape, are much harder to fake than the more modern digital media. Any clear photographic images of UFO's need to be examined by professional analysis to prove there has been no manipulation or faking of the image shown. Still, digital imagery is not totally useless as evidence of UFO's. There are complex professional methods to investigate even digital images to see if there is evidence of tampering. Along with the visual report of the photographer, coupled with a proven true image, much greater weight can be given to such evidence.

Radar contact coupled with a visual report, especially from a pilot in the air, can be compelling evidence that a UFO is real even if we don't yet know just what it is. While there are certain atmospheric phenomena that can give a false-positive reading, when a hard contact radar reading is matched to a visual sighting there can be little doubt that something is there. Photographic evidence of this same object provides a three-point proof of the existence of the object that is incredibly hard for even the most outrageous debunker to deny.
On the rare occurrences when a UFO has landed and left some trace of itself behind, proof of its existence can be very compelling. Among the traces left can be depressions in the ground where the landing struts have been, burned ground and vegetation, and occasionally a bit of metal or other anomalous piece of debris.

Stem node anomalies found in crop circle plants created by either electromagnetic or microwave radiation.
It is still the soil and plant matter that bears the greatest witness to a UFO landing. Samples analyzed in a professional, non-biased laboratory can provide proof of extreme radiation and uncharacteristic biochemical and electromagnetic readings that can provide clues as to what powered the craft that altered the soil it sat upon.
Professional and official ongoing research can also play a great part in providing the evidence to conclude the reality of UFO existence. One such research facility, Project Hessdalen in Norway, gets technical assistance not only from the Norwegian Defense Research Establishment, but the Universities of Oslo and Bergen as well. Using such devices as infrared, lasers, and radar, the Project has recorded a high number of unidentified objects in their viewing area. Two such events, dubbed the Hessdalen phenomena, have undergone more intense field research in hopes of discovering the nature of the lights observed and recorded.
The more solid and reputable proof that can be amassed and cross-referenced concerning the UFO phenomena, the stronger and harder to debunk the phenomena becomes. Combining all the evidence together can give us a better picture of how the craft operate and provide clues on how better to investigate them. By gathering the proof, rather than just hearsay, an answer to the UFO question is much more likely to be discovered.