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

Format of ASTER DEM
File Name(Example of N35~36,E135~136) ASTGTM_ N35E135_dem.tif ASTGTM_ N35E135_num.tif
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
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 10 years since its launch in December 1999
What ASTER tells us:
3D 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.