Height file Voordelta 2007

Coastal altitude model in the form of a grid with a resolution of 5 metres where the height value is recorded in meters. Parts of the sandy coast of the Netherlands are set in height every year for the production of beach profiles for monitoring coastline. A digital height model (DHM) is a file in which the height is displayed according to a regular, rectangular grid. Each cell of the grid (also called a grid cell) gets a height value. This height is calculated from the surrounding laser points of the filtered base file. The technique used for this purpose is a so-called weighted average interpolation. More information and explanations about the interpolation can be found in the manual on the grids of the AHN at www.ahn.nl. If there are no laser points near a grid cell, the cell remains empty (the cell gets a nodata value). Important to know is that the value of a 5x5 meter grid cell is calculated from multiple laser points (the number depends on the point density of the base file). As a result, the influence of the measurement noise and outliers decreases and a slight degree of flattening occurs.本数据集为分辨率5米的格网式海岸高程模型，高程值单位为米。荷兰部分沙质海岸每年均会开展高程更新工作，以生成用于海岸线监测的海滩剖面数据。数字高程模型（Digital Height Model, DHM）是一类基于规则矩形格网展示高程信息的文件，每个格网单元（亦称网格单元格）均对应唯一高程值。该高程值由滤波后的原始基准文件的周边激光点云数据计算得到，所采用的插值方法为加权平均插值法。有关该插值方法的更多细节与说明，请查阅AHN格网操作手册，网址为www.ahn.nl。若格网单元周边无可用激光点云数据，则该单元格将被赋予无数据值（nodata）。需特别说明的是，5米×5米的格网单元高程值由多个激光点云数据计算得到（具体点数取决于原始基准文件的点云密度）。此举可有效降低测量噪声与异常值的影响，但同时会带来轻微的高程扁平化现象。