Multi-resolution Ridge Top Flatness (MrRTF)

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.