Local-Area-Enhanced, 2.5-Meter Resolution Natural-Color and Color-Infrared Satellite-Image Mosaics of the North Takhar Mineral District in Afghanistan By Philip A. Davis and Laura E. Cagney U.S. Geological Survey Data Series 709-D 2012 U.S. Department of the Interior U.S. Geological Survey Abstract: The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Defense Task Force for Business and Stability Operations, prepared databases for mineral- resource target areas in Afghanistan. The purpose of the databases is to (1) provide useful data to ground-survey crews for use in performing detailed assessments of the areas and (2) provide useful information to private investors who are considering investment in a particular area for development of its natural resources. The set of satellite-image mosaics provided in this Data Series (DS) is one such database. Although airborne digital color- infrared imagery was acquired for parts of Afghanistan in 2006, the image data have radiometric variations that preclude their use in creating a consistent image mosaic for geologic analysis. Consequently, image mosaics were created using ALOS (Advanced Land Observation Satellite; renamed Daichi) satellite images, whose radiometry has been well determined (Saunier, 2007a,b). This part of the DS consists of the locally enhanced ALOS image mosaics for the North Takhar mineral district, which has placer gold deposits. ALOS was launched on January 24, 2006, and provides multispectral images from the AVNIR (Advanced Visible and Near-Infrared Radiometer) sensor in blue (420-500 nanometer, nm), green (520-600 nm), red (610-690 nm), and near-infrared (760-890 nm) wavelength bands with an 8-bit dynamic range and a 10-meter (m) ground resolution. The satellite also provides a panchromatic band image from the PRISM (Panchromatic Remote-sensing Instrument for Stereo Mapping) sensor (520-770 nm) with the same dynamic range but a 2.5-m ground resolution. The image products in this DS incorporate copyrighted data provided by the Japan Aerospace Exploration Agency ((c)JAXA,2006,2008), but the image processing has altered the original pixel structure and all image values of the JAXA ALOS data, such that original image values cannot be recreated from this DS. As such, the DS products match JAXA criteria for value added products, which are not copyrighted, according to the ALOS end-user license agreement. The selection criteria for the satellite imagery used in our mosaics were images having (1) the highest solar- elevation angles (near summer solstice) and (2) the least cloud, cloud-shadow, and snow cover. The multispectral and panchromatic data were orthorectified with ALOS satellite ephemeris data, a process which is not as accurate as orthorectification using digital elevation models (DEMs); however, the ALOS processing center did not have a precise DEM. As a result, the multispectral and panchromatic image pairs were generally not well registered to the surface and not coregistered well enough to perform resolution enhancement on the multispectral data. Therefore, it was necessary to (1) register the 10-m AVNIR multispectral imagery to a well-controlled Landsat image base, (2) mosaic the individual multispectral images into a single image of the entire area of interest, (3) register each panchromatic image to the registered multispectral image base, and (4) mosaic the individual panchromatic images into a single image of the entire area of interest. The two image- registration steps were facilitated using an automated control-point algorithm developed by the USGS that allows image coregistration to within one picture element. Before rectification, the multispectral and panchromatic images were converted to radiance values and then to relative- reflectance values using the methods described in Davis (2006). Mosaicking the multispectral or panchromatic images started with the image with the highest sun-elevation angle and the least atmospheric scattering, which was treated as the standard image. The band-reflectance values of all other multispectral or panchromatic images within the area were sequentially adjusted to that of the standard image by determining band-reflectance correspondence between overlapping images using linear least-squares analysis. The resolution of the multispectral image mosaic was then increased to that of the panchromatic image mosaic using the SPARKLE logic, which is described in Davis (2006). Each of the four-band images within the resolution-enhanced image mosaic was individually subjected to a local-area histogram stretch algorithm (described in Davis, 2007), which stretches each band's picture element based on the digital values of all picture elements within a 315-m radius. The final databases, which are provided in this DS, are three-band, color-composite images of the local-area- enhanced, natural-color data (the blue, green, and red wavelength bands) and color-infrared data (the green, red, and near-infrared wavelength bands). All image data were initially projected and maintained in Universal Transverse Mercator (UTM) map projection using the target area's local zone (42 for North Takhar) and the WGS84 datum. The final image mosaics were subdivided into nine overlapping tiles or quadrants because of the large size of the target area. The nine image tiles (or quadrants) for the North Takhar area are provided as embedded geotiff images, which can be read and used by most geographic information system (GIS) and image-processing software. The tiff world files (tfw) are provided, even though they are generally not needed for most software to read an embedded geotiff image. Disclaimer: Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Contact Information: If you have any questions regarding this dataset please feel free to contact: Philip A. Davis, Research Geologist U.S. Geological Survey 2255 North Gemini Drive, Building 4 Flagstaff, AZ 86001 pdavis@usgs.gov (928) 556-7084 ---------------------------------------------- This Data Series includes the following Information. ---------------------------------------------- DIRECTORY index_maps North_Takhar_Area-of-Interest_Index_Map.pdf -- Index map stored in Adobe Acrobat (PDF) format displaying the location of the North Takhar mineral district within Afghanistan in the geographic coordinate system. Index map is also provided in jpeg format. North_Takhar_Image_Index_Map.pdf -- Index map of the image products showing the extent of the target area and tile or quadrant scheme that was used to subdivide the image mosaics for the target area. This information is displayed on the topographic shaded-relief base map of Bohannon (2007a-c) in the UTM map projection and stored in both PDF and jpeg formats. image_files Local-area-enhanced, 2.5-m natural-color and color-infrared satellite-image mosaics in geotiff format with their tfw files. All images with their tfw and metadata files are compressed with standard file compression software to facilitate file transfer. metadata NORTH_TAKHAR_UTM_WGS84_Z42_NC_Qx.tif.txt -- FGDC compliant metadata files for each image tile or quadrant (designated by Qx). NC designates natural-color image data. NORTH_TAKHAR_UTM_WGS84_Z42_CIR_Qx.tif.txt -- FGDC compliant metadata files for each image tile or quadrant (designated by Qx). CIR designates color-infrared image data. shapefiles North_Takhar_Image_Mosaic_Index.shp -- A shapefile showing the boundary for the area of interest. index.html -- http://pubs.usgs.gov/ds/709/d/ 1_readme.txt -- This file. References Cited: Bohannon, R.G., 2007a, Topographic map of quadrangles 3768 and 3668, Imam-Saheb (215), Rustaq (216), Baghlan (221), and Taloqan (222) quadrangles, Afghanistan, U.S. Geological Survey Open-File Report 2005-1094-B, 1:250,000 scale, available at http://pubs.usgs.gov/of/2005/1094/B/. Bohannon, R.G., 2007b, Topographic map of quadrangles 3870 and 3770, Maymayk (211), Jamarj-i-Bala (212), Faydz-Abad (217), and Parkhaw (218) quadrangles, Afghanistan, U.S. Geological Survey Open-File Report 2005-1095-B, 1:250,000 scale, available at http://pubs.usgs.gov/of/2005/1095/B/. Bohannon, R.G., 2007c, Topographic map of quadrangle 3670, Jarm-Keshem (223) and Zebak (224) quadrangles, Afghanistan, U.S. Geological Survey Open-File Report 2005-1096-B, 1:250,000 scale, available at http://pubs.usgs.gov/of/2005/1096/B/. Davis, P.A.,2006, Calibrated Landsat ETM+ nonthermal-band image mosaics of Afghanistan: U.S. Geological Survey Open- File Report 2006-1345, 18 p., available at http://pubs.usgs.gov/of/2006/1345/. Davis, P.A., 2007, Landsat ETM+ false-color image mosaics of Afghanistan: U.S. Geological Survey Open-File Report 2007-1029, 22 p., available at http://pubs.usgs.gov/of/2007/1029/. Saunier, S., 2007a, Final calibration/validation report, PRISM: GAEL Consultant report, 27 p., accessed April 23, 2012, at http://earth.esa.int/pub/ESA_DOC/ALOS011.pdf. Saunier, S., 2007b, Final calibration/validation report, AVNIR-2: GAEL Consultant report, 25 p., accessed April 23, 2012, at http://earth.esa.int/pub/ESA_DOC/ALOS012.pdf.