You know my methods, Watson

Three police officers are up for promotion to CID. One's a graduate from Police College, a second is a University entrant and the third an old experienced beat bobby. The examiner gives each of them a barometer and tells them they have two hours to use it find out the height of the Town Hall spire.

When they return, the examiner asks the first - the Police College graduate - what his findings were and how he arrived at the answer.
"The spire's 90.5 metres high," says the graduate.
"Very close," said the examiner. "How did you arrive at that answer?"
"I paced out a base line from the town hall, got down and aligned the edge of the barometer with the spire and measured the angle between it and the ground. Then used trigonometry to work out the height."

Then the examiner asked the University graduate for his result. "I make it 90.2 metres," he said.
"Well within the acceptable margin of error." says the examiner. "And how did you get that answer?"
"I took a barometric reading at the base of the tower then climbed as high as I could inside the steeple and took a second reading. After that, it was simple to calculate the altitude."

The examiner turned to the beat bobby whose face showed years of wear from breaking up pub brawls. "What about you?"
"It's 90.365m," he said.
The examiner looks at him in surprise and says, "That's exactly right! How did you get such accuracy?"
"Easy," says the bobby. "I went to the Town Clerk's Office and told him to let me see the Town Hall plans or I'd hit him with the barometer."

LOL, really.

So obvious too.