Multi-resolution Ridge Top Flatness at 3 second resolution CSIRO 20000211

## **Abstract** 

This dataset and its metadata statement were supplied to the Bioregional Assessment Programme by a third party and are presented here as originally supplied



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. 



The 3 second resolution product was generated from the 1 second MrRTF product and masked by the 3" water and ocean mask datasets.

## **Dataset History** 

This dataset and its metadata statement were supplied to the Bioregional Assessment Programme by a third party and are presented here as originally supplied:



Data quality 

Lineage: 



Source data

1.	The 1 second MrRTF product

2.	3 second resolution SRTM water body and ocean mask datasets



MrRTF calculation

The 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.



Each 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.



Value    Threshold    Resolution

         slope (%)    (approx)

  0                      30 m

  1        16            30

  2         8            30

  3         4            90

  4         2           270

  5         1           800

  6         0.5         2.4 km

  7         0.25        7.2 km

  8         0.125        22 km

  9         0.0625       66 km



The 3 second version of MrRTF was derived from the 1 second MrRTF using the median value in each 3 x 3 group of 1 second cells.





Positional accuracy: 

The horizontal positional error is the same as for the raw SRTM 1 second data, with 90% of tested locations within 7.2 m for Australia. See Rodriguez et al. (2006) for more information.



Attribute accuracy: 

There is no clear geomorphic interpretation of the MrRTF index, so its accuracy is difficult to assess. Users are advised that the interpretation of the MrRTF index is likely to be sensitive to geomorphic context i.e. similar values mean different things in different areas. In some areas, high values of MrRTF index are associated with deeply weathered features where relatively flat areas high in the landscape have been preserved over a long period while surrounding areas have been eroded, exposing fresher material. 



The caveats for MrVBF (which does have a reasonably consistent geomorphic interpretation) are repeated here for information:

\*	In areas dominated by aeolian transport the assumptions behind the method are not met, and dunes (for example) are represented as erosional features with MrVBF = 0.

\*	Alluvial and colluvial fans are depositional but stand above their surroundings so often appear as erosional features with MrVBF = 0.





Logical consistency:

This product is a consistent representation of terrain based on the information in DEM-S.



Completeness:

The MrRTF product covers the same area as the source DEM-S, which is virtually all of continental Australia and near coastal islands. Some tiles containing parts of mainland or pieces of islands were not supplied at 1 second resolution and are therefore missing, see DEM-S metadata for details.

## **Dataset Citation** 

CSIRO (2000) Multi-resolution Ridge Top Flatness at 3 second resolution CSIRO 20000211. Bioregional Assessment Source Dataset. Viewed 27 November 2017, http://data.bioregionalassessments.gov.au/dataset/d29afa3d-2b3e-41c1-8c3f-e1b2500f16cc.

Tags: Cooper subregion, elevation
Organization: Bioregional Assessment Program