Features of ASTER G-DEM

Outline of ASTER GDEM

* Global DEM for all the land area covered by ASTER.
* Enhanced accuracy due to the use of multiple ASTER images over the same area.
* User-friendly, allowing selective cropping.

Concept of ASTER G-DEM development
World

Format of ASTER DEM

File Name(Example of N35~36,E135~136)	ASTGTM_ N35E135_dem.tif	ASTGTM_ N35E135_num.tif
File Name(Example of N35~36,E135~136)
Output format	GeoTIFF, signed 16 bits
Geographic coordinates	Geographic latitude and longitude
Tile Size	3601-by-3601 pixels (1-by-1 degree)
Posting interval	1 arc-second
DN values	1m/DN referenced to the WGS84/EGM96 geoid-9999 for void pixels, and 0 for sea water body	Stacking number or reference DEM SRTM3:-1,-2 CDED:-6 Alaska DEM:-11 etc.
Coverage	North 83 degrees to south 83 degrees, 22,600 tiles

*The detail is described in ReadMe file.

Comparison with other DEMs

	ASTER GDEM	SRTM3*	GTOPO30**	10 m mesh digital elevation data
Data source	ASTER	Space shuttle radar	From organizations around the world that have DEM data	1:25,000 topographic map
Generation and distribution	METI/NASA	NASA/USGS	USGS	GSI
Release year	2009 ~	2003 ~	1996 ~	2008~
Data acquisition period	2000 ~ ongoing	11 days (in 2000)
Posting interval	30m	90m	1000m	about 10m
DEM accuracy (stdev.)	7~14m	10m	30m	5m
DEM coverage	83 degrees north ~ 83 degrees south	60 degrees north ~ 56 degrees south	Global	Japan only
Area of missing data	Areas with no ASTER data due to constant cloud cover (supplied by other DEM)	Topographically steep area (due to radar characteristics)	None	None

Other examples of available DEMs
- NED: with a resolution of 30 m, covering the entire U.S.A., provided by USGS

*SRTM3: Shuttle Radar Topography Mission Data at 3 Arc-Seconds
**GTOPO30: Global 30 Arc-Second Elevation Data Set

Comparison between ASTER GDEM and SRTM3

Distinction from ASTER Level4Z DEM

ASTER Level4Z is provided for a given square of approximately 60 x 60 km corresponding to the scene acquired by ASTER. In contrast, ASTER GDEM is developed based on a grid of 1 x 1 degree in latitude and longitude and requires no scene selection or mosaicking.

About "ASTER" , an earth observing satellite sensor
What is ASTER?: ・An achievement from an international joint project between the Ministry of Economy, Trade and Industry of Japan (METI) and the National Aeronautics and Space Administration (NASA) ・An earth observing sensor developed in Japan to be onboard the satellite "Terra" ・In stable operation for more than 9 years since its launch in December 1999
What ASTER tells us: 1) Surface condition The sensor comprehensively captures spectral ranging from visible to thermal-infrared (invisible to the human eye), and offers detailed information on earth surface conditions (e.g. vegetation, geological features) together with their distribution. 2) Surface temperature Distribution of surface temperature can be observed by the thermal infrared sensor. This will be helpful to detailed studies of such phenomenon as the urban heat island effect. 3) DEM DEM is generated from a stereo-pair of images acquired with nadir and backward angles over the same area. ASTER GDEM will be developed based on this data.
Reference about ASTER ASTER Ground Data System (ASTER GDS) Project ASTER Science Project

Areas of DEM applications
1. Stereoscopic visualization of satellite and other two-dimensional images
Bird's-eye views and flight simulations can be generated by the combined use of DEM data and satellite or map data.

2. Automated calculation of slope direction and angle, catchment area, faults, etc.
Further achievements can be obtained by analyzing the DEM as a platform in combination with other data. Some examples are shown below.
* Disaster 1 (volcanic hazard map)
By a simulation using DEM as a platform, possible lava flow can be estimated. Local authorities can provide more advanced "volcanic hazard maps" that are crucial to ensure the safety of the residents.

* Disaster 2 (flood hazard map)
By simulating a process of rainfall, catchment, runoff and inundation using DEM as a platform, flood risk areas can be estimated. Local authorities can provide advanced "flood hazard maps" to the residents.

* Hydrology (water resource management)
Melted water is a valuable water resource in the oasis of Xinjiang Uyghur Autonomous Region, China. By calculating water catchment area using DEM, a potential water supply can be estimated even for unmapped areas. The obtained result can be utilized for water resource management in the oasis.

* Energy (oil resource exploration)
Oil source rock and reservoir formations are extracted from ASTER data. Strike and dip of those formations are measured from DEM, and a simulation of the underground geological structure will reveal their prospective anticlinal structure. In this way, oil and natural gas potentials can be evaluated without conducting a field investigation, even in an area of conflict.