This is "The Locator" (1968) by Robert Lory.
Gerard Bufus is, as noted, a very orderly person, even down to his pins:
Gerard Bufus was an orderly bachelor. He lived in an orderly apartment containing an orderly kitchen and bathroom and living room and library. The library was especially orderly. Even the colored pins in the map of the world on the wall were placed as closely parallel to the floor and to each other as Gerard Bufus could manage.
He is mapping UFO sightings/landings:
Each colored pin represented an authenticated report of a flying-saucer landing — either an actual landing or a documented observance of a UFO which when seen seemed to be looking for a place to land.
because he believes he can figure out a pattern:
"Living organisms intelligent enough to conquer the difficulties of space travel would have to be orderly people," Gerard Bufus explained once to an informal group of attendees at a Chicago convention of saucer buffs. "Their landings here — regardless of their intent — must be in accord with a harmonious pattern of place and time, a master plan. One would need only to discover that plan to be able to predict future landings accurately."
He succeeds in working out the pattern:
His first prediction was three weeks and four hundred miles away from a September landing south of Caracas, Venezuela. Two months more work and four landings later, he was within a square mile and two hours of a landing reported as a "strange event" near Cork, Ireland. There would be, according to the future-extended analog, three landings in far-distant places before the one came about that he could take advantage of.
He flies to Birmingham, NY and drives a rental car to the spot he has determined the UFO will land. The story ends:
Gerard Bufus' smile turned into an ear-shattering scream as the alien craft, large as a baseball diamond, crushed his neatly dressed body to jelly.
The landing was swift, orderly and precisely on target.
The story is available to be read in the February 1968 issue of The Magazine of Fantasy and Science Fiction at the Internet Archive.