Invercargill City Council staff member David McCormick said it had been identified that parts of the sign were pointing in the wrong directions.
''As work was needed to correct these, we are also taking the opportunity to improve the sign,'' he said.
University of Otago School of Surveying lecturer Paul Denys said a ''discrepancy'' in the sign was highlighted to him last year.
''You could tell that things weren't quite right when you actually did the calculations,'' he said.
Dr Denys used spherical trigonometry for his calculations, which was not the most accurate, but ''sufficient'' for the exercise, he said.
He found the signs pointing to Wellington and Cape Reinga were around the wrong way, and the sign's co-ordinates were out by 185m.
They were not mistakes any surveyor should have made, he said.
''Being a surveyor, that's our bread and butter in many respects, so we at least strive to be accurate.
''In this sort of case, I would imagine that a distance correct to a few kilometres would be appropriate, and more importantly, the directions are consistent with each other.''
Bluff Community Board chair Raymond Fife said some of the sign's blades were ''not pointing in quite the right direction''and the Invercargill City Council had been working towards making the amendments.
There was a ''fair bit of debate'' surrounding varying distances shown on the Stirling Point sign and a similar sign at Cape Reinga, he said.
Other changes to the sign would include the addition of Invercargill's ''sister city'' Suqian City, China, and Tokyo would be removed, he said.
Mr McCormick said he hoped the new sign would be installed within the next month.
