Sources des images

Toutes les images du site SEOS sont utilisées avec la permission explicite de leurs auteurs.
Elles ne peuvent pas être téléchargées sans la permission explicite des auteurs ! (voir aussi Disclaimer)

Images satellitaires

Western Europe (28-29/04/08). Sensor: SEVIRI/Meteosat-9, airmass product Source: EUMETSAT URL: http://oiswww.eumetsat.org/IPPS/html/DerivedProducts/MSG2/ AIRMASS/CENTRALEUROPE/index.htm Last access: 18.06.2008
Hurricane Charley (13/08/04). Sensor: SeaWiFS/Orbview-2 Source: Oceancolor/GSFC/NASA. URL: http://oceancolor.gsfc.nasa.gov/cgi/image_archive.cgi?c=STORMS Last access: 18.06.2008
Smoke and smog over Indonesia (22/10/97). Sensor: TOMS Earth-probe Source: NASA/GSFC URL: http://www.gsfc.nasa.gov/topstory/20010315ozone.html Last access: 18.06.2008
Ozone hole development (01/07/07 - 07/12/07). Sensor: OMI/Aura Source: NASA URL: http://ozonewatch.gsfc.nasa.gov/index.html Last access: 18.06.2008
Monthly average mid-tropospheric CO2 (July 2003). Sensor: AIRS/Aqua Source: NASA/JPL URL: http://photojournal.jpl.nasa.gov/catalog/PIA09269 Last access: 18.06.2008
Height of the ocean surface (Nov.97 and Feb.99). Sensor: TOPEX/POSEIDON and Jason 1 Source: NASA/JPL URL: http://www.windows.ucar.edu/tour/link=/earth/climate/enso.html Last access: 18.12.2008
Lena Delta, Russia (27/07/00). Sensor: Landsat 7 Source: NASA/JPL URL: http://earthasart.gsfc.nasa.gov/lena.html Last access: 18.06.2008
Monthly global images (2004). Sensor: MODIS/Terra Source: Reto Stockli, NASA Earth Observatory URL: http://earthobservatory.nasa.gov/Newsroom/BlueMarble/ BlueMarble_monthlies.html Last access: 18.12.2008
Global land cover of Africa (2000). Sensor: Vegetation/Spot 4 Source: Global Land Cover 2000 database, European Commission, Joint Research Centre, 2003 URL: http://www-tem.jrc.it/glc2000/interactive/glc2000_vgt.html Last access: 03.09.2008
Lake Ichkeul, Tunisia (14/11/01 and 29/07/05). Sensor: ASTER/Terra Source: NASA/GSFC/METI/ERSDAC/JAROS, and the U.S./Japan ASTER Science Team URL: http://earthobservatory.nasa.gov/Newsroom/NewImages/ images.php3?img_id=17159 Last access: 18.06.2008
Tungurahua Volcano, Ecuador (16/10/06). Sensor: ASTER/Terra Source: Nick Smith and Matt Patrick, Michigan Tech University; and Patricia Mothes, Instituto Geofísico, Escuela Politécnica Nacional URL: http://earthobservatory.nasa.gov/Newsroom/NewImages/ images.php3?img_id=17493 Last access: 18.06.2008
Namib desert, Namibia (8/12/00). Sensor: ETM+/Landsat 7 Source: USGS National Center for EROS and NASA Landsat Project Science Office URL: http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=10766 Last access: 18.06.2008
Deforestation in Bolivia (08/01/00). Sensor: ETM+/Landsat 7 Source: USGS EROS Data Center Satellite Systems Branch URL: http://earthobservatory.nasa.gov/Newsroom/NewImages/ images.php3?img_id=8260 Last access: 18.06.2008
Escondida mine, Chile (23/04/00). Sensor: ASTER/Terra Source: NASA/GSFC/METI/ERSDAC/JAROS and the U.S./Japan ASTER Science Team URL: http://earthobservatory.nasa.gov/Newsroom/NewImages/ images.php3?img_id=4492 Last access: 18.06.2008
Global biosphere and CO2. Sensor: SEaWiFs and ground data. Source: GSFC/NASA, SeaWiFS Project, GeoEye. URL: http://svs.gsfc.nasa.gov/vis/a000000/a003300/a003309/index.html Last access: 18.12.2008
Richat Structure, Mauritania. Sensor: Landsat (13/01/87) and Shuttle Radar Topography Mission (SRTM) data (01/02/00). Source: SRTM Team NASA/JPL/NIMA. URL: http://earthobservatory.nasa.gov/IOTD/view.php?id=4602 Last access: 14.01.2007
Bangladesh coastline (08/11/03). Sensor: MERIS/Envisat Source: ESA URL: http://www.esa.int/esaEO/SEMB7HD3M5E_index_0.html Last access: 01.07.2008
Atoll in the Pacific Ocean (23/09/01). Sensor: IKONOS Source: GeoEye URL: http://www.geoeye.com/gallery/ioweek/archive/01-09-23/index.htm Last access: 18.06.2008
Gulf Stream, Atlantic Ocean (27/05/07). Sensor: MODIS/Terra Source: SSEC EOS Direct Broadcast URL: http://eosweb.ssec.wisc.edu/browse_images/terra/2007/147/ 2007-05-27_0246-0257_GSTR_31_1KM.jpg Last access: 06.11.2009
White river, USA (14/04/06 and 07/04/08). Sensor: ASTER/Terra Source: NASA image created by Jesse Allen, using data provided courtesy of NASA/GSFC/METI/ERSDAC/JAROS and U.S./Japan ASTER Science Team URL: http://earthobservatory.nasa.gov/Newsroom/NewImages/ images.php3?img_id=18011 Last access: 01.07.2008
Wilkins shelf disintegration, Antartica (08/03/08). Sensor: Formosat-2 Source: Dr. Cheng-Chien Liu, National Cheng-Kung University and Dr. An-Ming Wu, National Space Organization, Taiwan URL: http://earthobservatory.nasa.gov/Newsroom/NewImages/ images.php3?img_id=17978 Last access: 01.07.2008
Oil spill in La Coruña, Spain (13/12/92 and 2/01/93). Sensor: SAR/ERS-1 Source: ESA URL: http://esamultimedia.esa.int/images/EarthObservation/corv_256.jpg Last access: 01.07.2008
Bay of Bisquay, Atlantic (17/05/04). Sensor: MERIS/Envisat Source: ESA URL: http://earth.esa.int/cgi-bin/satimgsql.pl?ids=472,4 Last access: 01.07.2008
Upwelling along the Sahara (22/03/02). Sensor: MERIS/Envisat Source: ESA URL: http://www.esa.int/esaEO/ESACGIF18ZC_index_1.html Last access: 18.12.2008
Durrat al Bahrain, Bahrain (01/04/07). Sensor: KOMPSAT-2 Source: KARI 2007, Distribution Spot Image URL: http://www.spotimage.fr/web/62-galerie.php?continent=6 Last access: 01.07.2008
San Francisco, USA (17/12/01) Sensor: Quickbird Source: DigitalGlobe URL: http://www.mapwindows.com/Free/FreeImage/RSImage/ San_Franciscoinfo.htm Last access: 01.07.2008
Kansas' fields, USA (24/06/01) Sensor: ASTER/Terra Source: NASA/GSFC/METI/ERSDAC/JAROS and the U.S./Japan ASTER Science Team URL: http://asterweb.jpl.nasa.gov/gallery-detail.asp?name=circles Last access: 01.07.2008
Vegetation vigour. Sensor: Quickbird data Source: DigitalGlobe URL: http://www.satimagingcorp.com/svc/land_cover_and_change_detection.html Last access: 01.07.2008
Nazca lines, Peru (10/11/02). Sensor: ETM+/Landsat 7 Source: Landsat USGS gallery URL: http://landsat.usgs.gov/gallery.php Last access: 01.07.2008
Low pressure system over Iceland (04/09/03). Sensor: Aqua/MODIS Source: Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC URL: http://visibleearth.nasa.gov/view_rec.php?id=6204 Last access: 17.12.2008
Typhoon Jelawat near the island of Minami Daito Jima, Japan (07/08/00). Sensor: SEaWIFS Source: SeaWiFS Project, NASA/GSFC and ORBIMAGE URL: http://visibleearth.nasa.gov/view_rec.php?id=713 Last access: 01.07.2008
Development of Hurricane Isabel (September 2003). Sensor: Meteosat-8 Source: EUMETSAT URL: http://oiswww.eumetsat.org/WEBOPS/iotm/iotm/ 20030908_hurricane/20030908_hurricane.html Last access: 17.12.2008
Hurricane Katrina (28/08/05). Sensor: MODIS/Terra Source: MODIS Rapid Response Team, GSFC/NASA URL: http://earthobservatory.nasa.gov/ images/imagerecords/15000/15395/Katrina2_TMO_2005240_lrg.jpg Last access: 17.12.2008
Rio de Janeiro Port, Brasil (20/04/02). Sensor: IKONOS Source: © 2007 GeoEye URL: http://www.satimagingcorp.com/gallery-ikonos.html Last access: 03.07.2008
Dust storm over China (07/04/01). Sensor: Vegetation/SPOT 4 Source: Vegetation programme, VITO URL: http://www.vgt.vito.be/AShtml/c34_07042001_china.htm Last access: 03.07.2008
Niau atoll, one of nearly 80 coral reef atolls forming the Tuamotu Archipelago in French Polynesia (06/10/05). Sensor: Proba Source: SSTL through ESA URL: http://earth.esa.int/cgi-bin/satimgsql.pl?pf=1273 Last access: 04.07.2008
Floods in the Irrawaddy delta caused by the cyclone Nargis that hit Myanmar (03/05/08). Sensor: ASAR/Envisat Source: ESA URL: http://www.esa.int/esaEO/SEMV0TZXUFF_environment_0.html Last access: 04.07.2008
Man-made islands located just off the coast of Dubai in the United Arab Emirates: Palm Jumeirah and The World (05/11/07). Sensor: Proba Source: N. Sullivan/SSTL through ESA URL: http://earth.esa.int/cgi-bin/satimgsql.pl?pf=1799 Last access: 04.07.2008
Center-pivot irrigation in Railroad Valley, Nevada, USA (17/08/01). Sensor: ASTER/Terra Source: NASA/GSFC/MITI/ERSDAC/JAROS and U.S./Japan ASTER Science Team URL: http://earthobservatory.nasa.gov/IOTD/view.php?id=1806 Last access: 18.02.2009
Lines and geoglyphs of Nazca in a Landsat-7 image (30 m resolution, 26/04/00) with details of a QuickBird image (0.6 m resoltuion, 16/09/02). Sensor: ETM+/Landsat 7 and Quickbird Source: Tokai University Research & Information Center, Japan URL: http://www.tric.u-tokai.ac.jp/isite/sarchaeology/enazca.html Last access: 04.07.2008
Cloud formation over Europe. Sensor: Meteosat Source: EUMETSAT 2008 URL: See Module 6 Last access: 03.02.2009
Fires raging across north-western Spain and Portugal (09/08/06). Sensor: Envisat Source: ESA URL: http://earth.esa.int/cgi-bin/satimgsql.pl?ids=1477 Last access: 03.02.2009
Lake Chad in Africa in 1972 and then later in October 2001. Sensor: not communicated Source: UNEP/GRID-Sioux Falls URL: http://na.unep.net/AfricaLakes/site_images.html Last access: 03.02.2009
Great zoom into the Amazon, Brazil. Sensor: MODIS/Terra, ETM+/Landsat 7 and IKONOS data Source: NASA/GSFC/Scientific Visualization Studio URL: http://svs.gsfc.nasa.gov/vis/a000000/a002500/a002550/index.html Last access: 03.02.2009
Dust storm in Northern Africa (01/03/05). Sensor: MODIS/Aqua Source: NASA/GSFC/MODIS Rapid Response Team, Jacques Descloitres URL: http://visibleearth.nasa.gov/view_rec.php?id=6567 Last access: 03.02.2009
Deforestation in Mato Grosso, Brazil, between 2002 and 2006. Sensor: MODIS/Terra Source: NASA/GSFC/MODIS Rapid Response Team, Robert Simmon URL: http://earthobservatory.nasa.gov/IOTD/view.php?id=6811 Last access: 03.02.2009
The apparent displacement of the building caused by the change of observation point is the parallax. Sensor: SPOT Source: Gent University, Belgium URL: See Module 10 Last access: 03.02.2009
Suspended Particulate Matter (SPM) map. Sensor: SeaWIFS Source: Institute for Environmental Studies (VU-IVM) URL: See Module 7 Last access: 03.02.2009
Identification of stressed vegetation. Sensor: Aviris data Source: USGS URL: http://speclab.cr.usgs.gov/PAPERS.veg1/vegispc2.html Last access: 03.02.2009
Chichen Itza, Mexico (05/03/01). Sensor: IKONOS Source: GeoEye © 2006 Satellite Imaging Corporation URL: http://news.satimagingcorp.com/2007/ 07/satellite_images_of_seven_wonders_of_the_world.html Last access: 03.02.2009

Autres images

Meteosat-9. Source: ESA URL: http://www.esa.int/msg/pag4.html Last access: 01.07.2008
The climate zones of the world. Source: www.wikimedia.org URL: http://en.wikipedia.org/wiki/File:ClimateMapWorld.png Last access: 17.12.2008
The Orbview-2 satellite. Photo: Orbital Sciences Corporation URL: http://www.orbital.com/images/Low/ov2_low.jpg Last access: 01.07.2008
Damage from Hurricane Charley on Captiva Island, Florida. Photo: NOAA/Tampa Bay National Weather Service URL: http://en.wikipedia.org/ wiki/Image:Hurricane_Charley_Captiva_Damage.jpg Last access: 06.08.2008
Damage caused to a gas station in Kissimmee, Florida, by Hurricane Charley. Photo: Wikipedia URL: http://en.wikipedia.org/wiki/Image:CharleyDamageInOrlando.jpg Last access: 06.08.2008
Arrival of hurricane Katrina in Mississipi. Photo: Anonymous URL: http://lh3.ggpht.com/_wwXBhk41cZc/RkdbB4BI4KI/AAAAAAAAANA/ cGOEkJoGwfM/Katrina1.jpg Last access: 17.12.2008
Burning the rain forest to clear land for oil palm tree in Sumatra, Indonesia. Photo: © WWF-Canon/Mark Edwards URL: http://www.panda.org/about_wwf/where_we_work/asia_pacific/ where/indonesia//environmental_problems_indonesia/index.cfm Last access: 01.07.2008
TOMS-Earth Probe. Photo: NASA URL: http://library01.gsfc.nasa.gov/cgi-bin/gdprojs/searchAlpha.pl?letter=T Last access: 03.07.2008
The Lidar at Davis station helps us to study ozone. Photo: © M.Lambert/Australia Antartic Division Australia Antartic Division URL: http://www.classroom.antarctica.gov.au/6-climate/6-5-ozone-depletion Last access: 01.09.2009
On the trail of the missing ozone. Source: EPA's Region 9 Office in San Francisco, California URL: http://www.epa.gov/ozone/science/missoz/index.html Last access: 01.07.2008
Dobson unit scale. Source: Eumetsat/DLR URL: http://wdc.dlr.de/sensors/gome2/ Last access: 01.07.2008
The Aqua satellite is part of the "A-Train" which consists of five satellites flying in formation around the globe. Source: NASA URL: http://www-calipso.larc.nasa.gov/about/atrain.php Last access: 03.07.2008
Aqua was launched aboard a Delta 7920-10L rocket at 2:55 a.m. PDT on May 4, 2002. Photo: NASA/Bill Ingalls URL: http://earthobservatory.nasa.gov/Library/Aqua/Aqua3.html Last access: 03.07.2008
This confused ice passenger clearly shows how climate change is affecting the Arctic. Photo: © Arne Nævra/Shell Wildlife Photographer of the Year URL: http://www.aftenposten.no/english/local/article2069092.ece Last access: 03.07.2008
Atmospheric concentrations of important greenhouse gases over the last 2,000 years. Source: IPCC 2007 URL: http://www.ipcc.ch/graphics/graphics/ar4-wg1/jpg/faq-2-1-fig-1.jpg Last access: 17.12.2008
Comparison of observed continental- and global-scale changes in surface temperature with results simulated by climate models using either natural or both natural and anthropogenic forcings. Source: IPCC 2007 URL: http://www.ipcc.ch/graphics/graphics/ar4-wg1/jpg/spm4.jpg Last access: 17.12.2008
Pacific Ocean under normal conditions. Source: W.S. Kessler, NOAA/PMEL URL: http://faculty.washington.edu/kessler/ENSO/enso_normal_new.gif Last access: 18.12.2008
Pacific Ocean under El Niño conditions (onset). Source: W.S. Kessler, NOAA/PMEL URL: http://faculty.washington.edu/kessler/ENSO/enso_onset_new.gif Last access: 18.12.2008
Pacific Ocean under El Niño conditions (peak). Source: W.S. Kessler, NOAA/PMEL URL: http://faculty.washington.edu/kessler/ENSO/enso_peak_new.gif Last access: 18.12.2008
Landsat 7 satellite in the cleanroom prior to launch. Photo: NASA/GSFC URL: http://landsat.gsfc.nasa.gov/about/landsat7.html Last access: 03.07.2008
Artist's rendering of the Terra spacecraft. Source: NASA/GSFC/Reto Stockli URL: http://visibleearth.nasa.gov/view_rec.php?id=114 Last access: 03.07.2008
Artist's rendering of the Terra spacecraft. Source: NASA URL: http://terra.nasa.gov/About/ Last access: 03.07.2008
Artist's impression of Envisat. Source: ESA URL: http://esamultimedia.esa.int/images/IP/ENVISATcorv_258.jpg Last access: 03.07.2008
Envisat's instruments. Source: Aviso URL: http://www.aviso.oceanobs.com/fr/missions/missions-actuelles/envisat/instruments/index.html Last access: 26.01.2009
The World Heritage site of Abu Simbel, Egypt. Photo: WHC UNESCO URL: http://whc.unesco.org/en/169/ Last access: 03.07.2008
The Blue Marble. Source: NASA URL: http://visibleearth.nasa.gov/view_rec.php?id=2429 Last access: 03.07.2008
Classification legend. Source: Global Land Cover 2000 database, European Commission, Joint Research Centre, 2003 URL: http://www-gem.jrc.it/glc2000 Last access: 03.07.2008
Artist's view of SPOT 5. Source: NOAA Coastal Services Center URL: http://www.csc.noaa.gov/crs/rs_apps/sensors/spot.htm Last access: 03.07.2008
The volcano Tungurahua on 28/11/04. Photo: Martin Zeise URL: http://en.wikipedia.org/wiki/Image:Equador_Tungurahua.JPG Last access: 04.07.2008
Tungaruhua on eruption on 2/11/99. Photo: Alcinoe Calahorrano/USGS URL: http://volcanoes.usgs.gov/Imgs/Jpg/Tungurahua/ 19991102_Tung_caption.html Last access: 04.07.2008
Soil degradation. Photo: ESA URL: http://www.esa.int/esaEO/SEMHLU3J2FE_environment_0.html Last access: 04.07.2008
The Namib Desert. Photo: Julien Fauqueur URL: http://docs.ufrmd.dauphine.fr/java/projets/manip_images/download/ Namibia7.jpg Last access: 04.07.2008
World desert's map. Distribution of non-polar arid land. Source: USGS URL: http://pubs.usgs.gov/gip/deserts/what/world.html Last access: 18.12.2008
Jungle burned for agriculture in Chiapas, Mexico. Photo: Jami Dwyer URL: http://en.wikipedia.org/wiki/Image:Lacanja_burn.JPG Last access: 04.07.2008
Submarine view of Tarawa reefs, Kiribati, Pacific Ocean (April 1994). Photo: Linda Wade/NOAA's Coral Kingdom Collection URL: http://www.photolib.noaa.gov/htmls/reef0485.htm Last access: 04.07.2008
This red tide is a toxic algal bloom. Photo: Alexander Mustard/NOCS
Dead fish caused by an HAB event. Photo: Alexander Mustard/NOCS
Marine phytoplankton seen through a microscope. Photo: N. Sullivan/NOAA/Department of Commerce URL: http://www.esa.int/esaEO/SEMQMYTQMFF_planet_1.html#subhead1 Last access: 04.07.2008
Upwelling animation. Winds blowing across the ocean surface push water away from an area and subsurface water rises up to replace the diverging surface water. Photo: NOAA URL: http://oceanservice.noaa.gov/education/kits/currents/03coastal4.html Last access: 18.12.2008
Major upwelling areas along the world's coasts are highlighted in red. Photo: NOAA URL: http://oceanservice.noaa.gov/education/kits/currents/media/ upwelling_image1.jpg Last access: 18.12.2008
Center-pivot irrigation effectively delivers much-needed water to crops in eastern Washington. Photo: Pacific Northwest National Laboratory URL: http://picturethis.pnl.gov/PictureT.nsf/All/477QCL?opendocument Last access: 04.07.2008
Monkey, bird and spider geoglyphs. Photo: Association Dr. Maria Reiche URL: http://www.htw-dresden.de/~nazca/Englisch/bilder2.htm Last access: 04.07.2008
Per capita greenhouse gas emissions by country in 2000 by country in 2000 (including land-use change). Source: Wikimedia Commons URL: http://en.wikipedia.org/wiki/Image:GHG_per_capita_2000.svg Last access: 20.11.2008
Greenhouse gas emissions by country in 2000 by country in 2000 (including land-use change). Source: Wikimedia Commons URL: http://en.wikipedia.org/wiki/Image:GHG_by_country_2000.svg Last access: 20.11.2008
Bengladesh Population Density within and outside of a 10m Low Elevation Coastal Zone. Source: CIESIN, Columbia University, 2000 URL: http://sedac.ciesin.columbia.edu/wdc/map_gallery.jsp Last access: 20.11.2008
The Glasshouse, RHS Wisley Garden, Surrey, UK (08/08/07). Photo: Wikimedia Commons, Mark Boyce URL: http://commons.wikimedia.org/wiki/File:RHSGlasshouse.JPG Last access: 03.02.2009
Artist's view of the TOPEX/POSEIDON altimeter. Source: NASA URL: See module 8 Last access: 03.02.2009
Forest fruits from Barro Colorado Island, Panama. Source: Wikimedia Commons, Christian Ziegler URL: http://commons.wikimedia.org/wiki/ File:Forest_fruits_from_Barro_Colorado.png Last access: 03.02.2009
Land use change around the airport near El Médano, Tenerife. Source: Naumann 2008 Last access: 03.02.2009
The giant Escondida mine in Chile. Photo: BHP Billiton Group URL: http://www.theage.com.au/articles/2004/10/16/1097784094618.html?from=storylhs Last access: 03.02.2009
Gulf stream temperature and current velocity. Source: CIMAS URL: http://oceancurrents.rsmas.miami.edu/atlantic/gulf-stream.html Last access: 03.02.2009
Oil slick visible on water's surface above the sunken battleship USS Arizona in Pearl Harbor, Hawaii. Photo: Wikimedia Commons © James G. Howes, November, 2005 URL: http://commons.wikimedia.org/wiki/File:USS_Arizona_oil_seepage.jpg Last access: 03.02.2009
Phaeocystis blooms can produce unpleasant foam which often accumulates on beaches. Photo: IVM URL: See Module 7 Last access: 03.02.2009
A field of cauliflowers, between two fields of lettuce and potatoes. Photo: The Regional Institute Ltd, Sydney, Australia URL: http://www.regional.org.au/au/gia/06/169sedat.htm Last access: 03.02.2009
View of the temple of warriors, Pre-Hispanic City of Chichen-Itza, Mexico. Photo: © UNESCO/Thierry Jolly URL: See Module 2 Last access: 03.02.2009
Ozone layers. Source: NASA URL: http://www.nasa.gov/centers/goddard/news/topstory/2003/0617eyes.html Last access: 03.02.2009
Movies: ozone formation, CFC destruction and ozone destruction. Source: NASA/GSFC/Scientific Visualization Studio URL: http://svs.gsfc.nasa.gov/stories/solve/ozone.html Last access: 03.02.2009
Satellites Ikonos, Quickbird, Orbview-3 and Formosat-2. Source: MEPSYD, ISFTIC URL: http://concurso.cnice.mec.es/cnice2006/material121/unidad3/ Last access: 06.02.2009
Satellite GeoEye-1. Source: © GeoEye URL: http://www.mundobits.com/?attachment_id=206 Last access: 06.02.2009
Satellite WorldView-1. Source: © DigitalGlobe URL: http://soswindows.free.fr/news/google/ Last access: 06.02.2009
Satellite Kompsat-2. Source: © 2002 KRSC URL: http://krsc.kari.re.kr/eng/satellite/satellite_01_2_msc.htm Last access: 06.02.2009

Toggle: Debug