TRIM DEM data will be used to interpolate a grid at an even 25 metre spacing. The eastings and northings will be gridded so they are evenly divisible by 25 metres. The eastings and northings of the outside extents of the data shall be evenly divisible by 100 metres. Please note that this requirement, in conjunction with the 250 metre margin requirement, may mean the actual extents of the data will be greater that either requirement would otherwise demand. Indefinite DEM Points shall be given less weight than DEM Points.
All elevations interpolated are to be stored to the nearest metre.
This will prevent double or erroneously weighting of the elevation values during the interpolation process. Ninety percent of all points interpolated from the TRIM DEM shall be accurate to within 10 metres of their true elevation. Holes in the DEM grid will not be acceptable. Lakes and oceans will have DEM points interpolated across their surfaces at even 25 metre intervals. These elevations may have variations in the water body surface however they must meet the above accuracy specification.