Aster Gdem

ASTER GDEM

ASTER GDEM is an easy-to-use, highly accurate DEM covering all the land on earth, and available to all users regardless of size or location of their target areas.Anyone can easily use the ASTER GDEM to display a bird's-eye-view map or run a flight simulation, and this should realize visually sophisticated maps. By utilizing the ASTER GDEM as a platform, institutions specialized in disaster monitoring, hydrology, energy, environmental monitoring etc. can perform more advanced analysis. (See another page,"Application")

For example, in "GEOSS Project(**)", DEM is considered to be an important platform and thus ASTER GDEM is expected to make significant contribution.

*Kashmir3DKashmir3D is a multi-functional free software for making realistic bird's-eye views, landscape CG, flight simulation movies and panorama mountain views. It supports almost all the publicly available map/topographic data (sold or free) as well as ASTER GDEM.

**GEOSSGEOSS is an ambitious international project involving approximately 60 nations including the G8 member states (Japan included) and approximately 30 international organizations, aiming to establish within 10 years a comprehensive global-scale system that coordinates various existing and future observation facilities such as satellites and ground stations. This project is anticipated to provide valuable information for policy makers.

Schedule

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 DEMSRTM3:-1,-2CDED:-6Alaska 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 1999What ASTER tells us:1) Surface conditionThe 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 temperatureDistribution 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) DEMDEM 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 ASTERASTER Ground Data System (ASTER GDS) ProjectASTER 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.

GDEM Data Use

- Intended users GDEM data will be distributed to any users (individual/organization) who conduct work or research in 9 societal benefit areas (disaster, health, energy, climate, weather, ecosystem, agriculture, and biodiversity) defined by GEOSS (Global Earth Observation System of System).(Refer to GEOSS homepage URL: http://www.epa.gov/geoss/)

- PriceGDEM data will be provided free of charge to the users who utilize the data for the above purposes.

- User Registration and LoginTo obtain ASTER GDEM data, register on ASTER GDEM Distribution site.

- Conditions of ASTER GDEM useWhen registering, it is required to agree to the conditions of data use(Agreement for GDEM distribution and data use), such as prohibition of secondary distribution of GDEM original data, credit title obligation in the case of displaying GDEM original data or the products produced by GDEM on Internet, scientific journal or any other publications.Follow the below instructions on credit title.To display in the image"ASTER GDEM is a product of METI and NASA"To include in writingClearly describe that the original data of ASTER GDEM is the property of METI and NASA.

- ImmunityBecause there are known inaccuracies and artifacts in the data set, please use the product with awareness of its limitations.The data are provided "as is" and neither NASA nor METI/ERSDAC will be responsible for any damages resulting from use of the data.

- Information of Validation resultThe summary of validation on ASTER GDEM is described in the Read Me which is attached to downloaded data.-More detailed validation result is described in Validation Report.

METI and NASA Release ASTER Global DEM

The Ministry of Economy, Trade, and Industry (METI) of Japan and the United States National Aeronautics and Space Administration (NASA) today jointly released Version 1 of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM). Previously, METI and NASA announced their intent to contribute the ASTER GDEM to the Global Earth Observation System of Systems (GEOSS). Consequently, the ASTER GDEM is available at no charge to users worldwide via electronic download from the Earth Remote Sensing Data Analysis Center (ERSDAC) of Japan and from NASAs Land Processes Distributed Active Archive Center (LP DAAC).

ASTER Global DEM

The ASTER instrument was built by METI and launched onboard NASAs Terra spacecraft in December 1999. It has an along-track stereoscopic capability using its near infrared spectral band and its nadir-viewing and backward-viewing telescopes to acquire stereo image data with a base-to-height ratio of 0.6. The spatial resolution is 15 m in the horizontal plane. One nadir-looking ASTER VNIR scene consists of 4,100 samples by 4,200 lines, corresponding to about 60 km-by-60 km ground area.

The methodology used to produce the ASTER GDEM involved automated processing of the entire 1.5-million-scene ASTER archive, including stereo-correlation to produce 1,264,118 individual scene-based ASTER DEMs, cloud masking to remove cloudy pixels, stacking all cloud-screened DEMs, removing residual bad values and outliers, averaging selected data to create final pixel values, and then correcting residual anomalies before partitioning the data into 1-by-1 tiles. It took approximately one year to complete production of the beta version of the ASTER GDEM using a fully automated approach.

The ASTER GDEM covers land surfaces between 83N and 83S and is composed of 22,600 1-by-1 tiles. Tiles that contain at least 0.01% land area are included. The ASTER GDEM is in GeoTIFF format with geographic lat/long coordinates and a 1 arc-second (30 m) grid of elevation postings. It is referenced to the WGS84/EGM96 geoid. Pre-production estimated accuracies for this global product were 20 meters at 95 % confidence for vertical data and 30 meters at 95 % confidence for horizontal data.

Initial studies to validate and characterize the ASTER GDEM confirm that pre-production accuracy estimates are generally achieved for most of the global land surface, although results do vary and true accuracies do not meet pre-production estimates for some areas. In addition, Version 1 of the ASTER GDEM does contain certain residual anomalies and artifacts that affect the accuracy of the product and may be impediments to effective utilization for certain applications. Consequently, METI and NASA acknowledge that Version 1 of the ASTER GDEM should be viewed as experimental or research grade. Nevertheless, they are confident that the ASTER GDEM represents an important contribution to the global earth observation community.

ASTER GDEM tiles may be downloaded electronically from ERSDAC by visiting http://www.gdem.aster.ersdac.or.jp/and from the LP DAAC by visiting https://wist.echo.nasa.gov/~wist/api/imswelcome/.

Pre-release announcement (Jun.26,2009)

METI and NASA Announce Plans for ASTER Global DEM Release

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) was developed jointly by the Ministry of Economy, Trade, and Industry (METI) of Japan and the United States National Aeronautics and Space Administration (NASA). Initial studies to validate and characterize the ASTER GDEM recently were completed by NASA and METI, in cooperation with the U.S Geological Survey (USGS) and the Earth Remote Sensing Data Analysis Center (ERSDAC) of Japan, as well as with support from the U.S. National Geospatial-Intelligence Agency (NGA) and numerous other collaborators from around the world.

ASTER Global DEM

Following review of the validation results, METI and NASA have decided to jointly release the ASTER GDEM on June 29, 2009. Previously, METI and NASA announced their intent to contribute the ASTER GDEM to the Global Earth Observation System of Systems (GEOSS). Upon release, the ASTER GDEM will be available at no charge to users worldwide via electronic download from ERSDAC and from NASAs Land Processes Distributed Active Archive Center (LP DAAC) by visiting http://www.gdem.aster.ersdac.or.jp/ and https://wist.echo.nasa.gov/~wist/api/imswelcome/, respectively.

The ASTER instrument was built by METI and launched onboard NASAs Terra spacecraft in December 1999. It has an along-track stereoscopic capability using its near infrared spectral band and its nadir-viewing and backward-viewing telescopes to acquire stereo image data with a base-to-height ratio of 0.6. The spatial resolution is 15 m in the horizontal plane. One nadir-looking ASTER VNIR scene consists of 4,100 samples by 4,200 lines, corresponding to about 60 km-by-60 km ground area.

The methodology used to produce the ASTER GDEM involved automated processing of the entire 1.5-million-scene ASTER archive, including stereo-correlation to produce 1,264,118 individual scene-based ASTER DEMs, cloud masking to remove cloudy pixels, stacking all cloud-screened DEMs, removing residual bad values and outliers, averaging selected data to create final pixel values, and then correcting residual anomalies before partitioning the data into 1-by-1 tiles. It took approximately one year to complete production of the beta version of the ASTER GDEM using a fully automated approach.

The ASTER GDEM covers land surfaces between 83N and 83S and is composed of 22,600 1-by-1 tiles. Tiles that contain at least 0.01% land area are included. The ASTER GDEM is in GeoTIFF format with geographic lat/long coordinates and a 1 arc-second (30 m) grid of elevation postings. It is referenced to the WGS84/EGM96 geoid. Pre-production estimated accuracies for this global product were 20 meters at 95 % confidence for vertical data and 30 meters at 95 % confidence for horizontal data. Initial validation studies concluded that the ASTER GDEM generally meets the pre-production accuracy predications, but results do vary and include areas where GDEM accuracy does not meet the pre-production estimates.

The topography of the land surface is one of the most fundamental geophysical measurements of the Earth, and it is a dominant controlling factor in virtually all physical processes that occur on the land surface. Topography of the land surface also significantly controls processes within the overlying atmosphere, and it reflects the processes within the underlying lithosphere. Consequently, topographic information is important across the full spectrum of earth sciences, and the availability of an up-to-date, high resolution (1-arc-sec or less) global DEM has been a priority of earth scientists for a long time. The ASTER GDEM, with 30m grid postings and produced from a consistent primary data source, is expected to meet the requirements of many users for global topographic information.