Relief - Elevation Range over 300 m derived from 1" SRTM DEM-S

The elevation range measures the full range of elevations within a circular window and can be used as a representation of local relief. \n\nThe 300 m elevation range product was derived from the Smoothed Digital Elevation Model (DEM-S; ANZCW0703014016), which was derived from the 1 arc-second resolution SRTM data acquired by NASA in February 2000. \n\nThis collection includes data at 1 arc-second and 3 arc-second resolutions.\n\nThe 3 arc-second resolution product was generated from the 1 arc-second 300 m elevation range product and masked by the 3” water and ocean mask datasets.\nLineage: Source data\n1.\t1 arc-second SRTM-derived Smoothed Digital Elevation Model (DEM-S; ANZCW0703014016).\n2.\t1 arc-second 300 m elevation range product\n3.\t3 arc-second resolution SRTM water body and ocean mask datasets\n\n300 m focal range elevation calculation\nElevation range is the full range of elevation within a circular window (Gallant and Wilson, 2000). Focal range using a 300 m window was calculated for each grid point from DEM-S using a 300 m kernel. The different spacing in the E-W and N-S directions due to the geographic projection of the data was accounted for by using the actual spacing in metres of the grid points, and recalculating the grid points included within the kernel extent for each 1o change in latitude.\n\nThe 300 m focal range elevation calculation was performed on 1° x 1° tiles, with overlaps to ensure correct values at tile edges.\n\nThe 3 arc-second resolution version was generated from the 1 second 300 m elevation range product. This was done by aggregating the 1” data over a 3 x 3 grid cell window and taking the maximum of the nine values that contributed to each 3” output grid cell. The 3” 300 m elevation range data were then masked using the SRTM 3” ocean and water body datasets.\n\n\nReferences\nGallant, J.C. and Wilson, J.P. (2000) Primary topographic attributes, chapter 3 in Wilson, J.P. and Gallant, J.C. Terrain Analysis: Principles and Applications, John Wiley and Sons, New York.

高程极差指圆形邻域内高程值的全距，可用于表征局地地形起伏度。

300米高程极差数据集源自平滑数字高程模型（Smoothed Digital Elevation Model，简称DEM-S；编号ANZCW0703014016），而该平滑数字高程模型则由美国国家航空航天局（NASA）2000年2月获取的1角秒（arc-second）分辨率航天飞机雷达地形测绘任务（Shuttle Radar Topography Mission，SRTM）数据生成。

本数据集包含1角秒和3角秒两种分辨率的数据。

3角秒分辨率数据集由1角秒分辨率的300米高程极差数据集生成，并通过3角秒水体与海洋掩膜数据集完成掩膜处理。

数据溯源：源数据
1. 1角秒SRTM衍生平滑数字高程模型（DEM-S；ANZCW0703014016）
2. 1角秒分辨率300米高程极差数据集
3. 3角秒分辨率SRTM水体与海洋掩膜数据集

300米邻域高程极差计算
高程极差指圆形邻域内高程值的全距（Gallant与Wilson，2000）。以300米为邻域窗口的高程极差，通过300米核函数从DEM-S数据中逐网格点计算得到。由于数据采用地理投影，东西向与南北向的网格间距存在差异，为此通过采用网格点实际米制间距，并针对每1度纬度变化重新计算核函数范围内包含的网格点，以修正该投影带来的间距差异。

300米邻域高程极差计算以1°×1°的图幅为单元进行，并设置重叠区域以确保图幅边缘的计算值准确无误。

3角秒分辨率版本由1角秒分辨率的300米高程极差数据集生成：先将1角秒数据以3×3网格单元为窗口进行聚合，取每个3角秒输出网格单元对应的9个值的最大值，随后通过SRTM 3角秒海洋与水体数据集对300米高程极差数据完成掩膜处理。

参考文献
Gallant, J.C. 与 Wilson, J.P.（2000）《主要地形属性》，收录于Wilson, J.P. 与 Gallant, J.C. 所著《地形分析：原理与应用》第三章，约翰威立出版公司，纽约。