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I saw a file stating that New Zealand has 11 zones and was wondering how it was determined and divided, does anyone have any idea? the paper offers a short description that doesn't cover much information, enter image description here

So if anyone have any information that could help me and guide me that would be great. Thank you

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    $\begingroup$ There's no big secret here. Take meteorological data from whatever sources you have available and plot the sea-level pressure across the country over time. Then use those results to find the areas that tend to have similar sea-level pressure. What more do you want? $\endgroup$ Dec 19, 2022 at 9:33

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I suspect the purpose of the zones are being misunderstood. The zones do not represent geological areas that tend to share common pressures distinct from the other areas.

They’re atmospherically arbitrary boundaries that ensure that all aircraft in a defined airspace area are operating on the same altimeter settings. All aircraft in Otago use one identical setting, and an aircraft coming from Canterbury resets its altimeter to the Otago setting at the designated boundary.

This would be useful in any geography where the altimeter settings between two nearby airports could be different enough to cause altitude conflicts if two aircraft are each using a different airport’s settings.

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The reference to the AIP has most of the information you're after (AIP ENR 1.7-2). Interestingly there seems to now be 12 zones.

Screenshot from my phone: AIP ENR 1.7-2

Presumably, they created this after studying the historical QNH values and found they were similar within those areas. Pilots can use the zone QNH until they are within the vicinity of an aerodrome, when they switch to the aerodrome QNH.

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    $\begingroup$ Thank you for the answer Ben!Would you mind sharing the link? $\endgroup$
    – Zol613
    Dec 20, 2022 at 1:00

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