Terrain¶

Global GMTED2010 derived topographic variables¶

Using the http://topotools.cr.usgs.gov/gmted_viewer/ dataset (7.5 arc-seconds) several topographic variables have been calculated aggregating the value at 30 arc-seconds (GMTED2010_30arc-sec.tif reference file).
Computation done using gdaldem and pktools

File nomenclature: TopographicVariables_??_GMTED2010_??.tif

where ?? can assume the following meaning:

mn=mean
md=medean
mi=minimum
mx=maximum
sd=standard deviation

Percent of elevation values: threshold_????_GMTED2010_??.tif¶

• Percent of Minimum elevation values over (>=) a specific threshold, using Minimum Statistic, 7.5 arc-seconds (useful to identify the Minimum value of an elevation range). Aggregation done at 1km (0.00833 degree) by calculating percent of pixels (16 pixel) over the specific threshold.
• Percent of Median elevation values over (>=) a specific threshold, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating percent of pixels (16 pixel) over the specific threshold.
• Percent of Maximum elevation values over (>=) a specific threshold, using Maximum Statistic, 7.5 arc-seconds (useful to identify the Maximum value of an elevation range). Aggregation done at 1km (0.00833 degree) by calculating percent of pixels (16 pixel) over the specific threshold.

Elevation: elevation_??_GMTED2010_??.tif¶

• Maximum value of elevation, using Maximum Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the maximum values among 16 pixel.
• Minimum value of elevation, using Minimum Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the minimum values among 16 pixel.
• Median value of elevation, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the median values among 16 pixel.
• Mean value of elevation, using Mean Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the mean values among 16 pixel.
• Standard deviation of elevation, using Mean Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the standard deviation values among 16 pixel.
• Standard deviation of elevation, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the standard deviation values among 16 pixel.

Aspect: aspect-cosine_??_GMTED2010_??.tif, aspect-sine_??_GMTED2010_??.tif¶

• Maximum value of aspect cosine, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the cosine and calculating the maximum values among 16 pixel.
• Minimum value of aspect cosine, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the cosine and calculating the minimum values among 16 pixel.
• Mean value of aspect cosine, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the cosine and calculating the mean values among 16 pixel.
• Median value of aspect cosine, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the cosine and calculating the median values among 16 pixel.
• Standard deviation value of aspect cosine, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the cosine and calculating the standard deviation values among 16 pixel.

• Maximum value of aspect sine, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine and calculating the minimum values among 16 pixel.
• Minimum value of aspect sine, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine and calculating the maximum values among 16 pixel.
• Mean value of aspect sine, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine and calculating the mean values among 16 pixel.
• Median value of aspect sine, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine and calculating the median values among 16 pixel.
• Standard deviation value of aspect sine, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine and calculating the standard deviation values among 16 pixel.

Slope: slope_??_GMTED2010_??.tif¶

• Maximum value of slope, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the maximum values among 16 pixel.
• Minimum value of slope, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the minimum values among 16 pixel.
• Median value of slope, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the median values among 16 pixel.
• Mean value of slope, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the mean values among 16 pixel.
• Standard deviation of slope, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the standard deviation values among 16 pixel.

Eastness: eastness_??_GMTED2010_??.tif¶

• Maximum value of Eastness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine of slope * sine of aspect and calculating the minimum values among 16 pixel.
• Minimum value of Eastness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine of slope * sine of aspect and calculating the maximum values among 16 pixel.
• Mean value of Eastness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine of slope * sine of aspect and calculating the mean values among 16 pixel.
• Median value of Eastness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine of slope * sine of aspect and calculating the median values among 16 pixel.
• Standard deviation value of Eastness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine of slope * sine of aspect and calculating the standard deviation values among 16 pixel.

Northness: northness_??_GMTED2010_??.tif¶

• Maximum value of Northness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine of slope * cosine of aspect and calculating the minimum values among 16 pixel.
• Minimum value of Northness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine of slope * cosine of aspect and calculating the maximum values among 16 pixel.
• Mean value of Northness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine of slope * cosine of aspect and calculating the mean values among 16 pixel.
• Median value of Northness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine of slope * cosine of aspect and calculating the median values among 16 pixel.
• Standard deviation value of Northness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by deriving the sine of slope * cosine of aspect and calculating the standard deviation values among 16 pixel.

Roughness: roughness_??_GMTED2010_??.tif¶

• Maximum value of roughness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the maximum values among 16 pixel.
• Minimum value of roughness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the minimum values among 16 pixel.
• Median value of roughness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the median values among 16 pixel.
• Mean value of roughness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the mean values among 16 pixel.
• Standard deviation of roughness, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the standard deviation values among 16 pixel.

Terrain Ruggedness Index (TRI) tri_??_GMTED2010_??.tif¶

• Maximum value of TRI, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the maximum values among 16 pixel.
• Minimum value of TRI, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the minimum values among 16 pixel.
• Median value of TRI, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the median values among 16 pixel.
• Mean value of TRI, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the mean values among 16 pixel.
• Standard deviation of TRI, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the standard deviation values among 16 pixel.

Topographic Position Index (TPI) tpi_??_GMTED2010_??.tif¶

• Maximum value of TPI, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the maximum values among 16 pixel.
• Minimum value of TPI, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the minimum values among 16 pixel.
• Median value of TPI, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the median values among 16 pixel.
• Mean value of TPI, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the mean values among 16 pixel.
• Standard deviation of TPI, using Median Statistic, 7.5 arc-seconds. Aggregation done at 1km (0.00833 degree) by calculating the standard deviation values among 16 pixel.

Global DEM fusion¶

(Also see _WG collaborative notes and documents_)

Links¶

SRTM¶

• CGIAR-CSI 90m void-filled SRTM (request bulk download)
• SRTM home
• Global Land Cover Facility

• Redistribution policy:

Users are prohibited from any commercial, non-free resale, or redistribution without explicit written permission from CIAT. Users should acknowledge CIAT as the source used in the creation of any reports, publications, new data sets, derived products, or services resulting from the use of this data set. CIAT also request reprints of any publications and notification of any redistributing efforts. For commercial access to the data, send requests to Andy Jarvis.

ASTER¶

• ASTER home
• GDEM2 validation reports
  • See especially: Summary_GDEM2_validation_report_final.pdf

• Redistribution policy (excerpt below)

What restrictions apply to the redistribution of data?

The general principle is one of reversibility: If someone can recover the original x-y-z values from the new product, then that new product can NOT be re-distributed. This can also be defined as lossless recovery.

What are some examples of derived products that are re-distributable?

1. Reprojection that involved re-sampling, including nearest neighbor in cases where the reprojection involves more than a simple translation of an integer number of GDEM pixels

DEM fusion and related issues¶

• _*Elevation models for geoscience*_. Fleming C, Marsh SH, Giles JRA, eds (2010) Geological Society Special Publications, Vol 345.
  • Crippen: _Global topographical exploration and analysis with the SRTM and ASTER elevation models_
  • Nightingale and Morgan: _Refinement of ASTER digital elevation models using SRTM data for an environmental study in China_
• Fusion DEM project page at NASA Earth Exchange
• People:
  • John Gallant at CSIRO
  • Bob Crippen at JPL

DEM processing¶

• John Gallant on Adaptive smoothing for noisy DEMs
  • Talk
  • Paper

Related products¶

• GTOPO30: Global 1km DEM distributed out of EROS (1996)
• HYDRO1k: Global 1km derived topographic data based on GTOPO30
  • Raster products: hydrologically correct DEM, derived flow directions, flow accumulations, slope, aspect, compound topographic (wetness) index
  • Vector products: derived streamlines and basins
• GLOBE: Multi-source global 1km DEM out of NGDC (1999 v1.0)
• SRTM30: 30 second SRTM with void cells and polar regions filled by GTOPO30 (2005 v2.0)
• SRTM30_PLUS: SRTM30 plus seafloor topography (2009 v6.0)