Multi-resolution Ridge Top Flatness (MrRTF)
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MrRTF is a topographic index designed to identify high flat areas at a range of scales. It complements the MrVBF index that is designed to identify areas of deposited material in flat valley bottoms. Unlike MrVBF, the MrRTF index does not have a clear link to landform processes but it has been found to be a useful adjunct to MrVBF in landform classification. Zero values indicate areas that are steep or low, with values 1 and larger indicating progressively larger areas of high flat land. \n\nThis collection includes MrRTF data at 1 arc-second and 3 arc-second resolutions.\n\nThe 3 arc-second resolution product was generated from the 1 arc-second MrRTF product and masked by the 3” water and ocean mask datasets.\n\nLineage: Source data\n1.\tThe 1 arc-second SRTM DEM-S (ANZCW0703014016)\n2.\tThe 1 arc-second MrRTF product\n3.\t3 arc-second resolution SRTM water body and ocean mask datasets\n\nMrRTF calculation\nThe MrRTF and MrVBF method is described in Gallant and Dowling (2003). It is based on slope and position in landscape (ranking within a 3- or 6-cell circular window) calculated from the original DEM and progressively generalised DEMs. The algorithm used to create this product is version 6g-a5, which is slightly different to that in the original paper.\n\nEach value of MrRTF is associated with a particular scale and slope threshold. For each successive value the slope threshold halves and the scale triples. At each scale a location is assigned the value for that scale if it is sufficiently high (ranked above the majority of the surrounding cells) and flat (slope less than the threshold), and zero otherwise. The largest value takes precedence at each location.\n\nValue Threshold Resolution\n slope (%) (approx)\n 0 30 m\n 1 16 30\n 2 8 30\n 3 4 90\n 4 2 270\n 5 1 800\n 6 0.5 2.4 km\n 7 0.25 7.2 km\n 8 0.125 22 km\n 9 0.0625 66 km\n\nThe 3 arc-second version of MrRTF was derived from the 1 arc-second MrRTF using the median value in each 3 x 3 group of 1 arc-second cells.\n\n\nGallant, J.C. and Dowling T.I. (2003) A multiresolution index of valley bottom flatness for mapping depositional areas. Water Resources Research 39(12) 1347-1360.
多分辨率山脊顶平坦度指数（MrRTF）是一种用于识别多尺度下高平坦区域的地形指数，可作为多分辨率谷底平坦度指数（MrVBF）的补充工具——MrVBF旨在识别平缓谷底的沉积区域。与MrVBF不同，MrRTF并未与明确的地貌过程建立直接关联，但现有研究表明，其在地貌分类中可作为MrVBF的有效辅助手段。当MrRTF值为0时，代表该区域为陡峭地形或低地；值为1及以上时，则对应面积逐步增大的高平坦区域。 本数据集集合包含1弧秒与3弧秒两种分辨率的MrRTF数据。 3弧秒分辨率的产品由1弧秒分辨率的MrRTF数据生成，并通过3弧秒水体与海洋掩膜数据集完成掩膜处理。 数据谱系：源数据 1. 1弧秒航天飞机雷达地形测绘任务（SRTM）数字高程模型S（DEM-S，ANZCW0703014016） 2. 1弧秒分辨率MrRTF产品 3. 3弧秒分辨率SRTM水体与海洋掩膜数据集 MrRTF计算方法 MrRTF与MrVBF的计算方法详见Gallant与Dowling（2003）的研究成果。该方法基于由原始数字高程模型（DEM）及逐步泛化的DEM计算得到的坡度与景观位置特征（即3单元或6单元圆形窗口内的单元格排名）。本产品采用的算法版本为6g-a5，与原始论文中的算法存在细微差异。 每个MrRTF值均对应特定的尺度与坡度阈值。每递增一个数值，对应的坡度阈值将减半，而分析尺度则变为原来的三倍。在每个尺度下，若某位置满足足够平坦（坡度低于对应阈值）且为高值区域（在周边单元格中排名高于多数相邻单元格），则赋予该尺度对应的数值；否则赋值为0。每个位置最终以最大的可用数值作为结果。 | MrRTF值 | 近似坡度阈值（%） | 分辨率 | | ---- | ---- | ---- | | 0 | - | 30米 | | 1 | 16 | 30米 | | 2 | 8 | 30米 | | 3 | 4 | 90米 | | 4 | 2 | 270米 | | 5 | 1 | 800米 | | 6 | 0.5 | 2.4千米 | | 7 | 0.25 | 7.2千米 | | 8 | 0.125 | 22千米 | | 9 | 0.0625 | 66千米 | 3弧秒分辨率的MrRTF产品是通过对1弧秒分辨率的MrRTF数据中每3×3的单元格组求取中值得到的。 Gallant, J.C. 与 Dowling, T.I.（2003）《用于绘制沉积区地图的多分辨率谷底平坦度指数》，《水资源研究》，39(12)：1347-1360。
