Some GIS Spatial data sources

Across the years, I've been occasionally in need for geospatial data, whether a World Map, or a Satellite backdrop to a small map for a city, a free satellite image or shapefile was very important.
Luckily, many data sources exist in the Internet that have been published by many Space and satellite-owning agencies across the world, and many derived data that can enhance any map.

Some of my more important sources:
Global Land Cover Facility (GLCF)
http://glcf.umiacs.umd.edu/
A great source for many satellite imagery products and datasets, it can be accessed through ftp and provide wealth of file formats and resolutions, must check it.

NASA LandSat GeoCover data set
https://zulu.ssc.nasa.gov/mrsid/mrsid.pl
It provides access to LandSat Mosaics that has been created for most of the globe in 2 time eras (1990 and 2000), it delivers MrSID compressed mosaics with 15m pixel size.

StatSilk List of downloadable free shapefiles
http://www.statsilk.com/maps/download-free-shapefile-maps
Provides a list of downloadable shapefiles that contains many datasets.

Global Administrative Areas
http://www.gadm.org/
Provides shapefiles for administrative boundaries for the countries.

Blue Marble Next Generation
http://earthobservatory.nasa.gov/Features/BlueMarble/
(Direct download) ftp://neo.sci.gsfc.nasa.gov/bluemarble/bmng/bmng_arcview/
The Blue Marble is a gorgeous dataset, it provides 500m imagery for the whole world that is color processed and provides a great basemap backdrop for World Maps.

True Marble (by Unearthed Outdoors)
http://www.unearthedoutdoors.net/global_data/true_marble/download
Another global dataset that is created from LandSat imagery, this time the data has been color and band processed to provide a more natural color and appearance of the imagery, but the full resolution 15m imagery are available for purchase only, in the link you can download the the 250m images.

Global Land Cover 2000 (by the EU JRC)
http://bioval.jrc.ec.europa.eu/products/glc2000/glc2000.php
The Global Land Cover objective is to become a harmonized land cover database over the whole globe, it provides Land Cover maps for the whole world and can be utilized in many analysis functions (mostly on the national level).

New Global DEM released from METI and NASA

The Ministry of Economy, Trade, and Industry (METI) of Japan and the United States National Aeronautics and Space Administration (NASA) at 29th of June jointly released Version 1 of the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) Global Digital Elevation Model (GDEM).

Some information about the ASTER instrument:

• Building Agency: METI of Japan
• Carrier Spacecraft: USA NASA’s Terra
• Launch date: December 1999
• Stereoscopic capability: Along-track (no need to pass multiple times over the same area to collect stereo image data)
• Bands available for DEM generation: VNIR (near infrared spectral band)
• DEM base-to-height ratio: 0.6
• Spatial resolution: 15m in the horizontal plane
• Single ASTER VNIR scene size: About 60 km-by-60 km ground area (4,100 samples by 4,200 lines)

Some information about the ASTER GDEM:

• Land surface coverage: between 83°N and 83°S
• Grid cell size: 1 arc-second (30 m)
• Tiles Format: GeoTIFF
• Number of tiles: 22,600
• Single tile size: 1°-by-1°
• Coordinate System Type: Geographic (Lat/Long coordinates)
• Earth Model: WGS84/EGM96 geoid
• Collection Date: 2000-2009
• Vertical accuracy estimate: 20 meters (at 95 % confidence)
• Horizontal accuracy estimate: 30 meters (at 95 % confidence)
• Area of missing data: Areas with constant cloud coverage

This mission is remarkable because it involved the automated processing of the entire 1.5-million-scene ASTER archive, it took approximately one year to complete production of the beta version of the ASTER GDEM using a fully automated approach.

The process included:

1. Stereo-correlation to produce 1,264,118 individual scene-based ASTER DEMs
2. Cloud masking to remove cloudy pixels
3. Stacking all cloud-screened DEMs
4. Removing residual bad values and outliers
5. Averaging selected data to create final pixel values
6. Correcting residual anomalies
7. Partitioning the data into 1°-by-1° tiles.

Previously, the most complete Global DEM publicly available was the SRTM (Shuttle Radar Topography Mission), it has an 80% land coverage (between 60°N and 57°S). The ASTER GDEM expands coverage to 99%; also the SRTM data has a grid cell size of 3 arc-seconds (90 m) outside of the USA borders, despite being captured at 1 arc-second, it was later averaged before being publicly released.

I hope that NASA would release the full resolution 1 arc-second data of the SRTM DEM globally to augment the ASTER GDEM data and allow for a unified DEM which benefits from the ability of the Radar to collect data in the places constantly covered by clouds.

I currently don't know the shoreline data used to outline the DEM data, but I hope they release it as well or use a publicly available one, such as the NGA Prototype Global Shoreline (PGS) data.

A good technical page about the new ASTER GDEM can be found here.

METI and NASA marks version 1 of the ASTER GDEM as “experimental” or “research grade”, but the size and accuracy of the data makes such an initial release a very good step toward a highly enhanced and accurate Global DEM very near.

Download sources:

Earth Remote Sensing Data Analysis Center (ERSDAC) of Japan

NASA’s Land Processes Distributed Active Archive Center (LP DAAC)

I will post shortly about my experience with the download of the new GDEM and its estimated size and usage characteristics.

Sources and News Coverage:

NASA’s Land Processes Distributed Active Archive Center

The Map Room, Astronomy Magazine, Universe Today, BBC News