iii
Contents
Introduction.....................................................................................................................................................1
Existing GTOPO30 Elevation Model ............................................................................................................1
GMTED2010 Dataset Characteristics .........................................................................................................2
Input Data Sources ........................................................................................................................................2
Data Preprocessing .......................................................................................................................................5
Generalization.................................................................................................................................................6
Mosaicking......................................................................................................................................................7
Pixel Alignment and Grid Coordinates .......................................................................................................7
Output Data Products ....................................................................................................................................9
Data Formats.................................................................................................................................................12
Generalized Elevation Products – Seamless Global Coverage (GRID) ......................................12
Generalized Elevation Products – Tile-Based (GeoTIFF Image Format) ....................................12
Spatially Referenced Metadata (ESRI Vector Shapefile Format) ...............................................12
Accuracy Assessment ................................................................................................................................12
Raster-Based Assessment ................................................................................................................12
Absolute Vertical Accuracy Assessment .......................................................................................12
Limitations and Caveats ..............................................................................................................................21
Summary........................................................................................................................................................21
References Cited..........................................................................................................................................22
Appendix........................................................................................................................................................25
Figures
1. Map showing GTOPO30 elevation model .................................................................................1
2. Map showing GTOPO30 elevation sources ..............................................................................2
3. Map showing SRTM DTED
®
2 (void-filled) 1-arc-second coverage .....................................3
4. Map showing 15-arc-second SPOT 5 Reference3D Africa coverage .................................4
5. Diagram showing aggregate example using the maximum value (3 x 3 processing
window) ..........................................................................................................................................6
6. Diagram showing standard deviation example using blockstd routine (3 x 3 processing
window) ..........................................................................................................................................7
7. Diagram showing ArcGIS mosaic – blend method .................................................................8
8. Diagram showing “Pixel center” referencing of full resolution 1-arc-second SRTM
data .................................................................................................................................................8
9. Diagram showing spatial nesting of GMTED2010 pixels .............................................................8
10. Diagram showing the GMTED2010 layer extents (minimum and maximum latitude and
longitude) are a result of the coordinate system inherited from the 1-arc-second SRTM
data ................................................................................................................................................10
11. Graphic showing comparison of the existing GTOPO30 and new GMTED2010 30-arc-
second mean elevation product ...............................................................................................10
12. Map showing GMTED2010 spatially referenced metadata with void polygons having
a dark dense appearance .........................................................................................................11