Other formats

    TEI XML file   ePub eBook file  


    mail icontwitter iconBlogspot iconrss icon

Nelson Historical Society Journal, Volume 3, Issue 6, October 1980

The Standard Survey Chain Test Marks

page 14

The Standard Survey Chain Test Marks

(This information was supplied by Mr Holcroft to the Nelson Committee of the Historic Places Trust and printed in a Newsletter 1979. We are grateful for permission to reprint.)

The first land surveys in Nelson were carried out by New Zealand Company surveyors, and later (1852 to 1876) by surveyors under the control of the Provincial Government. There was no independent check on the accuracy of these surveys and this, both in Nelson and other of the early settlements, caused uncertainty and confusion in the survey records. Therefore, on the abolition of the provinces in 1876, a New Zealand wide system was started whereby all surveys were to be connected to permanent marks fixed by triangulation.

The unit of measurement for all surveys was a "chain of 100 links." For many years a linked chain (invented by Edmund Gunter about 1620) was used; this was superseded by the more convenient steel and invar tape capable of being wound on a drum. Today (1979) measurements are metric and electronic devices are being used for determining distances.

Both the linked chain and the tapes were subject to hard wear in the field and it was essential that any variation from the standard chain was known – and so a "standard test chain" was included in the survey equipment brought to Nelson in 1841 by the New Zealand company Survey Party.

At the start of the triangulation work in 1877, one of the first tasks was to lay down "Standard Chain" lengths at Nelson and Ahaura, and later at Collingwood and Westport. Surveyors were required to check their chains or bands against these test bases at regular intervals. In Nelson some of these base marks have survived, but those on the West Coast and Collingwood are apparently gone. Of the five chain test base which ran along the eastern side of the Ministry of Works buildings, one mark remains – a shaped stone with an inset metal plate, now nearly level with the road formation; and in front of the new Court Building, close to, and parallel with Bridge Street, is the concrete slab of a One-Chain Base. Inset metal plates marking one end, and one intermediate point are visible.

In 1902 it was considered necessary to make further checks on the standard of length in use. Twelve new bands were obtained from London, one being placed in the custody of each Chief Surveyor. Each band was tested and certified by the Standard Department of the Board of Trade as being in agreement with the Imperial Standard. In Nelson the differences found, although small, were sufficient to require the recalculation of the triangulation.