The Maritime Zones Act 2013 states that the contiguous zone comprises those areas of the sea that are beyond and adjacent to the territorial sea, having as their outer limits a line measured seaward from the baseline, every point of which is distant 24 nautical miles from the nearest point of the baseline.
The Contiguous Zone Outer Limits Notice 2013, No. 2013/2C further states the relevant coordinates for the contiguous zone of Niue. Most important is that it highlights the geodetic framework in which the geographic coordinate is determined by reference to the World Geodetic System 1984 (WGS 84). It also shows charts that illustrates the lines described under the schedule of coordinates.
https://www.un.org/Depts/los/LEGISLATIONANDTREATIES/PDFFILES/niu_contiguous_zone_outer_limit_notice2013.pdf
https://www.un.org/Depts/los/LEGISLATIONANDTREATIES/PDFFILES/niu_maritime_zones_act_2013.pdf