Spot Heights are identified as two types.
Type 1 were observed photogrammetrically and were captured for mapping purposes for the 1:25000 series maps and placed where necessary to depict topography not clearly shown by contours. Also used to indicate high points (hill tops), saddles and low points in depressions.
Type 2 were generated by interpolation and were strictly used for DEM generation purposes.
Type 1 spot heights were collected by photogrammetric observation of 1:42000 photography models used for 1:25000 scale mapping and 10 metre VI contouring.
Accuracy is only provided in terms of height for this feature as its positional accuracy was only relevant to the relative contours and usually not pointing to a well defined feature.
Stated accuracy is 90% of elevation information is within 5 metres in height in areas free of vegetation at the time of collection.
Type 2 spot heights are not provided with an accuracy as they are interpolated from the contours and as such cannot be relied upon.