Licensing options for this format begin with FME Professional Edition.
The Terrain Tiles on AWS reader provides FME with access to elevation data in a variety of tile-based formats. It is an Amazon Web Services (AWS) Public Dataset that can be accessed free of charge.
Overview
Terrain tile data is available in four formats:
- Terrarium (PNG): A 24-bit fixed point representation of elevation in meters, split over the red, green, and blue bands. To decode:
(red * 256 + green + blue / 256) - 32768
- Normal (PNG): A 3-D vector representing the surface direction, and an 8-bit elevation value. The red, green and blue bands hold the x, y and z magnitudes, respectively. The alpha band contains quantized elevation data, with more opaque cells representing lower elevation.
- GeoTIFF (GeoTIFF): Raw 16-bit integer elevation data in meters, suitable for analysis.
- Skadi (SRTM HGT): 16-bit elevation data in meters, in unprojected WGS84 coordinates.
For more information on these tile formats, visit https://aws.amazon.com/public-datasets/terrain/.
Data Sources
Use of these terrain tiles for either analysis or display requires attribution. For details, see https://aws.amazon.com/public-datasets/terrain/.
The dataset is derived from the following open data sources:
- 3DEP (formerly NED) in the United States, 10 meters outside of Alaska, 3 meter in select land and territorial water areas
- SRTM globally except high latitudes, 30 meters in land areas
- GMTED globally, coarser resolutions at 7.5”, 15”, and 30” in land areas
- ETOPO1 to fill in ocean bathymetry at 1’
Please note that while the product may appear to be available at a high resolution, tiles will have been oversampled from coarser source data where finer resolution was not available.
Reader Overview
The reader downloads terrain tiles from Amazon S3 based on a spatial filter. The tiles are cached to disk and read by the underlying PNGRASTER, GEOTIFF, or SRTMHGT format reader.
Note: On Windows, this format caches downloads in the temp folder. FME attempts to limit the size of the cache based on the value specified in the Cache Limit field under Tools > Options > Translation> Web File Cache.
FME Raster Features
FME raster features represent raster data and use several concepts that are unlike those used in the handling of vector data. The topics below describe how FME processes raster data.