How does Satellite
Photo (Image) work?

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Satellite Photo - How does it work?

 

InfraRed Visible Water Vapor InfraRed

Satellite Photo   Bringing the finest High Resolution Satellite and  Aerial Photos for many different uses

Color enhanced imagery is a method meteorologists use to aid them with satellite interpretation. The colors enable a meteorologist to easily and quickly see features which are of special interest to them. Usually they look for high clouds or areas with a large amount of water vapor.
In an infrared (IR) image cold clouds are high clouds, so the colors typically highlight the colder regions. In a water vapor image, white areas indicate moisture and dark areas indicate little or no moisture, so the colors typically highlight areas with large amounts of moisture.

About the Satellite Images

Infrared (IR) images | Visible images | Water Vapour channel
Image Updates | Time Stamps | Browsing the Archive

Infrared (IR) images

IR images are derived from radiation emitted from the Earth and its atmosphere at thermal-infrared wavelengths (10-12 µm). They provide information on the temperature of the underlying surface or cloud.

IR images are available 24 hours per day because temperatures can always be measured, regardless of day or night. (This is in contrast to Visible images which are only available during the day. See below.) The temperatures are represented either by a grey-scale (black is no-cloud, and increasing white means higher colder clouds), or in a colour scheme (900Kb).

IR imagery is available on: NOAA 15, 14, 12, 11 etc.: Channel 4: 10.3-11.3 µm Channel 5: 11.5-12.5 µm GOES-9: Channel 4: 10.2-11.2 µm Channel 5: 11.5-12.5 µm GMS 5: IR1 10.3-11.3 IR2: 11.5-12.5 µm FY-2: IR1: 10.5-12.5 µm MTSAT: IR1: 10.3-11.3 IR2: 11.5-12.5 µm

Visible images

Visible (VIS) images are a record of the visible light scattered or reflected towards the satellite from the Earth and clouds. i.e. you can 'see' the clouds. Visible images give meteorologists extra information that may not appear on Infrared temperature images. For example, fog appears in Visible images, but may not in Infrared images when the fog and the land are at the same temperature.

Visible images are only available during the daytime, because at night the world looks black. VIS images are normally displayed in a manner similar to that seen by the human eye. Using a black and white colour scale, with different shades of grey indicating different levels of reflectivity, the brightest and most reflective surfaces are in white tones and the least reflective in black. In general, clouds are seen as white objects against the darker background of the earth's surface.

Visible imagery is available on:

• NOAA 15, 14, 12, 11 etc.: Channel 1: 0.58-0.68 µm Channel 2: 0.725-1.10 µm
• GOES-9: Channel 1: 0.55-0.75 µm
• GMS 5: VIS 0.55-0.8 µm
• FY-2: VIS 0.5-1.05 µm
• MTSAT: VIS 0.55-0.8 µm

Water Vapour channel

Water Vapour imagery is derived from radiation emitted by water vapour at wavelengths around 6-7 µm. This is not an atmospheric window but a part of the spectrum where water vapour is the dominant absorbing gas. The centre of the absorbing band is 6.7µm.

The water vapour channel is available on GOES-9, GMS, FY-2 and MTSAT.

Image Updates

The time stamp on the images is the start time of the reception of the top of the image from the satellite. It takes approximately 30 minutes for GOES-9 to complete a scan and the image is generally available on the Web within 30 minutes of completion, i.e an hour after the time stamp.

Time stamps

Satellite images are time stamped in "UTC" (Coordinated Universal Time), which is equivalent to GMT or Z time (Greenwich Mean Time). This is the start time of the reception of the top of the image from the satellite. It takes approximately 30 minutes for GOES-9 to complete a scan and the image is available on the Web within 30 minutes of completion, i.e an hour after the time stamp.

Below is a comparison of current UTC to current Eastern Standard Time (EST), Central Standard Time (CST) and Western Standard Time (WST) or the Daylight Saving equivalent.

To convert UTC times to local Australian times, add the time difference between your Australian time zone and UTC. For daylight saving add an extra hour to the difference between Australian times and UTC. During daylight saving, the difference for (EDT) i.e. New South Wales, Victoria and Tasmania is 11 hours instead of 10, and the difference for South Australia (CDT) is 10.5 hours instead of 9.5.

Browsing the Archive

A browse service provides free access to browse images for Visible (1:32 resolution) or Infrared (1:8 resolution) channels to assist with the selection of required dates and times for ordering higher resolution images or radiances from the Bureau's Satellite Data Archive.

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• Will DIRECWAY VoIP work with my existing DW6000 or DW4020 system?
• Can I sign up to the service and use a PC client instead of an analogue phone and the DW6040 to connect to my DW6000/DW4020?
• Is a specific grade of service plan needed for DIRECWAY VoIP?
• Is there a minimum contract term?
• Can I have more than one telephone number?

IP Videophone

Will DIRECWAY VoIP work with my existing DW6000 or DW4020 system?

DIRECWAY VoIP comprises a voice appliance known as the DW6040. The DW6040 is designed and optimized to work with the DW6000 and the DW4020 Internet access terminals. If you have any other DIRECWAY system, speak to your dealer about upgrade options.
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Can I sign up to the service and use a PC client instead of an analogue phone and the DW6040 to connect to my DW6000/DW4020?

No, the service is designed and optimized to work with the DW6040 and provides constant bit rate support to ensure voice traffic is prioritized over other data traffic. PC client software is not available and is not currently supported.
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Is a specific grade of service plan needed for DIRECWAY VoIP?

All existing service plans from HNSE will support voice over IP.
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Photo courtesy XM Satellite Radio Satellite radio broadcasters promise crystal-clear music transmitted from thousands of miles into space.

For more information on satellite radio and related topics, check out the links on the next page.

What support is available?

TerraServer contains 3.3 tera-bytes of high resolution USGS aerial imagery and USGS topographic maps. You can locate imagery by clicking on the map above, entering a city or town name in the "Search TerraServer" form at the top of the page, or entering a U.S. street address. Click on Advanced Find to see other methods for searching our imagery database.

Below are sample thumb-nail images of famous places contained in the TerraServer database. Click on a thumb-nail image to see a famous place or click on more famous places to see a complete the complete list images of famous sites.

	Click on the  thumbnail to  download DW6040 System User's Guide (PDF, 1,059K)			Click on the   thumbnail to   download   DIRECWAY VoIP document  (PDF, 1,820K)
	Click on the  thumbnail to download DW6040 System Configuration Data Sheet (PDF, 58K)			Click here if you need  to download free   Acrobat Reader®   software

These images come from satellites which remain above a fixed point on the Earth (i.e. they are "geostationary"). The infrared image shows the invisible infrared radiation emitted directly by cloud tops and land or ocean surfaces. The warmer an object is, the more intensely it emits radiation, thus allowing us to determine its temperature. These intensities can be converted into greyscale tones, with cooler temperatures showing as lighter tones and warmer as darker.

Lighter areas of cloud show where the cloud tops are cooler and therefore where weather features like fronts and shower clouds are. The advantage of infrared images is that they can be recorded 24 hours a day. However, low cloud, having similar temperatures to the underlying surface, are less easily discernable. Coast-lines and lines of latitude and longitude have been added to the images and they have been altered to northern polar stereographic projection.

The infrared images are updated every six hours with the 0000, 0600, 1200 and 1800 UTC images. It usually takes about 20 minutes for these images to be processed and be updated on the website. The time shown on the image is in UTC.

	MapMart is a fantastic source all kinds of data, both for the US and worldwide. Make this your source for aerial and satellite imagery, scanned topographic maps, and vector street maps.
USGS Geographic Data Download	SDTS 10m and 30m DEM data for the United States The USGS Geographic Data Download site is the central repository for USGS 1:250K DEMs (digital elevation model and satellite imagery), USGS 1:100K and 1:24K DLGs (Digital Line Graphic), and USGS LULC (land use and land cover) data. Of course, all of this data is ABSOLUTELY FREE for download.
EROS Data Center	The Earth Resources Observation Systems (EROS) Data Center (EDC) is a data management, systems development, and research field center for the U.S. Geological Survey's (USGS) National Mapping Division. Data searching and ordering may be performed through a variety of information management systems and interfaces, including: The USGS Global Visualization Viewer (GloVis) is a quick and easy online search and order tool for selected satellite data. GloVis provides greater data availability, allowing a researcher mosaic visual access to browse satellite images from the Landsat 7 ETM+, Landsat 4/5 TM, Landsat 1-5 MSS, MRLC, and Landsat Orthorectified data sets, as well as Aster TIR and Aster VNIR browse satellite images from the DAAC inventory. USGS's Earth Explorer data discovery and access tool is the replacement information system for the Global Land Information System (GLIS). All of the searchable data sets found within GLIS will be migrated to Earth Explorer this year. The new Earth Explorer functionality includes a secure credit card/e-commerce system and cross-inventory search capabilities that greatly expand the data discovery and access tools USGS can offer to it's customers. Photo Finder is a World Wide Web-based, quick-search tool for locating and ordering photographs from the USGS' National Aerial Photography Program. Map Finder is a World Wide Web-based, quick-search tool for locating and ordering 7.5-minute (1:24,000-scale) USGS maps of the conterminous United States. The EOS Data Gateway is a NASA World Wide Web-based query system. This information management system provides information on a variety of data sets, including documentation, satellite image browse (depending upon the data set), and ordering services.
USGS Seamless Data Distribution Center	The USGS Seamless Data Distribution Center provides access to several USGS data sets, including the following: NED (National Elevation Data Set) - supplies 30-m resolution seamless elevation data for the entire continental US Urban Areas High-Resolution Satellite Orthoimagery - supplies 1 foot resolution aerial imagery for the largest urban areas in the US Shuttle Radar Topography Mission (SRTM) - supplies high resolution elevation data for much of the earth
NGA Digital Nautical Charts	The Digital Nautical Chart® is produced by the National Geospatial-Intelligence Agency (NGA) and is an unclassified, vector-based, digital database containing maritime significant features essential for safe marine navigation. The NGA Digital Nautical Charts site offers a large selection of marine charts in DNC format for free download. Initial data collection of the database is from a portfolio of approximately 5,000 nautical charts that will ultimately provide global marine navigation between 84° North latitude and 81° South latitude and support a variety of Geographic Information System applications.
NOAA Electronic Navigational Charts	NOAA National Environmental Satellite, Data and Information Service - NESDIS operates the satellites and manages the processing and distribution of millions of bits of data and satellite images these satellites produce daily. The prime customer for the satellite data is the NOAA National Weather Service, which uses satellite data to create forecasts for television, radio, and weather advisory services. Click here for the home page of NOAA Satellites and Information (National Environmental Satellite, Data and Information Service). The NOAA Electronic Navigational Charts site offers a large selection of NOAA marine charts in S-57 format for free download. S-57 charts can be viewed in Global Mapper v6.00 and above.
NGA Raster Roam	ASTER 30m International DEM Data ASTER DEM data provided the first high-resolution alternative to DTED0.  ASTER DEMs are available in HDF or Geotiff format. HDF is a self-describing format (like SDTS or shapefiles) that very few applications recognize. More can handle geotiff, but not the I16 or FP32 that ASTER DEMs are offered in. As a result, it takes more work than the casual user is willing to expend in order to use this data. Nevertheless, it is an extremely important data set and is expanding as more users request on-demand DEMs. See the article. This data is available at: The NGA Raster Roam site offers several NIMA data sets for free download, included VMAP levels 0 and 1, DTED level 0, ONC, and TPC data.
VMAP 1 Download from MapAbility	The MapAbility VMAP1 Downloads page provides a simpler alternative to the NGA Raster Roam site for obtaining VMAP level 1 data. Vector Map (VMap) Level 0 is an updated and improved version of the National Satellite Imagery and Mapping Agency's (NIMA) Digital Chart of the World (DCW®). The VMap Level 1 database provides worldwide coverage of vector-based geospatial data which can be viewed at 1:1,000,000 scale, i.e. 1cm=10km. It consists of geographic, attribute, and textual data stored on CD-ROM or as downloaded files. The primary source for the database is the 1:1,000,000 scale Operational Navigation Chart (ONC) series co-produced by the military mapping authorities of Australia, Canada, United Kingdom, and the United States.
GIS Data Depot	The GIS Data Depot offers a wide variety of data, including 1:24K USGS DEM data for the US, 1:24K USGS DRGs (scanned topo maps), and a large selection of satellite imagery and vector data products.
National Atlas of the USA	The updated National Atlas is designed to provide a reliable summary of national-scale geographical information. Though it cannot provide detailed map information, the Atlas directs users to other sources for this information. Most data is available in Shapefile, GeoTIFF, or SDTS vector format.
GeoBase Canada	GeoBase Canada provides a large assortment of FREE data for Canada, including Landsat-7 satellite imagery, 1:50K and 1:250 CDED elevation data, a National Road database in Shapefile format, and the Canadian Geographic Names data set in Shapefile format.
NASA LandSat 1990 Download	This NASA site provides FREE LandSat satellite imagery for most of the Earth's land masses circa 1990. The GeoCover Landsat mosaics are delivered in a Universal Transverse Mercator (UTM) / World Geodetic System 1984 (WGS84) projection.  The mosaics generally extend north-south over 5 degrees of latitude, and span east-west for the full width of the UTM zone.  For mosaics between 60 degrees north and 60 degrees south latitude, the width of the mosaic is the standard UTM zone width of 6 degrees of longitude.  For mosaics above 60 degrees of latitude, the UTM zone is widened to 12 degrees, centered on the standard UTM meridian.  To insure overlap between adjacent UTM zones, each mosaic extends for at least 50 kilometers to the east and west, and 1 kilometer to the north and south.

 

IR Sensors IR imagery is available on: NOAA 15, 14, 12, 11 etc.: Channel 4: 10.3-11.3 µm Channel 5: 11.5-12.5 µm GOES-9: Channel 4: 10.2-11.2 µm Channel 5: 11.5-12.5 µm GMS 5: IR1 10.3-11.3 IR2: 11.5-12.5 µm FY-2: IR1: 10.5-12.5 µm MTSAT: IR1: 10.3-11.3 IR2: 11.5-12.5 µm

NOAA 15 Channel 4 10.3-11.3 µm	NOAA 15 Channel 5 11.5-12.5 µm
NOAA 14 Channel 4 10.3-11.3 µm	NOAA Channel 5 11.5-12.5 µm

Visible images

Visible (VIS) images are a record of the visible light scattered or reflected towards the satellite from the Earth and clouds. i.e. you can 'see' the clouds. Visible images give meteorologists extra information that may not appear on Infrared temperature images. For example, fog appears in Visible images, but may not in Infrared images when the fog and the land are at the same temperature.

The intensity of the image depends on the albedo/reflectivity of the underlying surface or cloud. Visible images are only available during the daytime, because at night the world looks black. Early morning 7am VIS images show the sunlight rising in the east, and the 7pm VIS images show the sun setting in the west.

VIS images are normally displayed in a manner similar to that seen by the human eye. Using a black and white colour scale, with different shades of grey indicating different levels of reflectivity, the brightest and most reflective surfaces are in white tones and the least reflective in black. In general, clouds are seen as white objects against the darker background of the earth's surface. The brightness also depends on the intensity of the reflectivity and the relative positions of the sun and satellite with respect to the earth. Shadows and highlights can be seen where the sun shines obliquely on to cloud. [Source Bader et al, 1995]

Visible imagery is available on:

• NOAA 15, 14, 12, 11 etc.: Channel 1: 0.58-0.68 µm Channel 2: 0.725-1.10 µm
• GOES-9: Channel 1: 0.55-0.75 µm
• GMS 5: VIS 0.55-0.8 µm
• FY-2: VIS 0.5-1.05 µm
• MTSAT: VIS 0.55-0.8 µm
  

GMS 5 VIS 0.55-0.8 µm

Water Vapour channel

Water Vapour imagery is derived from radiation emitted by water vapour at wavelengths around 6-7 µm. This is not an atmospheric window but a part of the spectrum where water vapour is the dominant absorbing gas. The centre of the absorbing band is 6.7µm.

Emissions from water vapour low in the atmosphere will not normally escape to space. If the upper troposhpere is moist, the radiation reaching the satellite will mostly originate from this (cold) region and be displayed in white shades, following the IR imagery colour convention. Only if the upper atmosphere is dry will will radiation originate from water vapour at warmer, mid-troposheric levels and be displayed in darker shades on the image. In normally moist atmosphere , most of the WV radiation recieved by the satellite originates in the 300-600 hPa layer, but when the air is dry some radiation may come from layers as low as 800hPa. Because of the general poleward decrease of water vapour content, the height of the contributing layer gets lower towards the poles. [Source Bader et al, 1995]

The water vapour channel is available on GOES-9, GMS, FY-2 and MTSAT.

GMS 5 Water Vapour Image: 6.5-7.0 µm

Image Updates

The time stamp on the images is the start time of the reception of the top of the image from the satellite. It takes approximately 30 minutes for GOES-9 to complete a scan and the image is generally available on the Web within 30 minutes of completion, i.e an hour after the time stamp. Sometimes an image is missed due to scheduled maintenance outages or a systems failure. The images remain available for 7 days.

Time Stamps

Satellite images are time stamped in "UTC" (Coordinated Universal Time), which is equivalent to GMT or Z time (Greenwich Mean Time). This is the start time of the reception of the top of the image from the satellite. It takes approximately 30 minutes for GOES-9 to complete a scan and the image is available on the Web within 30 minutes of completion, i.e an hour after the time stamp.

The colour enhanced imagery web pages also have the equivalent time in Eastern Standard Time (EST). One hour needs to be added during daylight saving.

Below is a comparison of current UTC to current Eastern Standard Time (EST), Central Standard Time (CST) and Western Standard Time (WST) or the Daylight Saving equivalent.

Visible images are only available during daylight hours, approximately EST 7am-7pm (21Z-09Z).

To convert UTC times to local Australian times, add the time difference between your Australian time zone and UTC. For daylight saving add an extra hour to the difference between Australian times and UTC. During daylight saving, the difference for (EDT) i.e. New South Wales, Victoria and Tasmania is 11 hours instead of 10, and the difference for South Australia (CDT) is 10.5 hours instead of 9.5.

Aerial photography and satellite photography work in similar fashion. Course and speed are set before entering the area to be photographed, to ensure uniformity of speed and altitude. The result is an image of a narrow strip, which can be combined with overlapping images of neighboring strips to produce a panoramic view, commonly called a mosaic. Commercially available aerial and satellite photographs are capable of resolving objects of about 10 sq ft (1 sq m), which means that a satellite would be able to distinguish between a car and truck. Aerial photographs may be high oblique (including the horizon), low oblique (below the horizon), or vertical (perpendicular to the earth). Only the vertical may be accurately scaled for mapmaking purposes. Often a multilens camera is used to photograph one section vertically and the adjacent areas obliquely. The individual oblique exposures are then corrected, scaled, and joined to the vertical section to form one continuous photograph. By viewing two overlapping photographs through a stereoscope, a three-dimensional image of a region, or topographic map, can be obtained.

Images can also be produced at other wavelengths, such as microwave or infrared, by using a technique known as remote scanning, which measures variations in spectral reflectance rather than patterns of light and shadow. Remote scanning aids such disparate fields as archaeology, geology, forestry, highway construction, and land conservation. The best-known remote scanners are the Landsat series of satellites, which have mapped vegetation and geological formations on the earth's surface since 1972; the French SPOT series, first launched in 1986; Magellan, which used radar to map the planet Venus (1990); Lunar Prospector, which mapped the moon's surface composition and its magnetic and gravity fields (1998); Mars Global Surveyor, which engaged in a systematic mapping of Mars (1999); and Galileo, which returned pictures of Jupiter and its major moons (1995–2003).

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http://southport.jpl.nasa.gov/desc/imagingradarv3.html

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http://www.ecotarium.org/exhibits/earthfromspace/game/qpages/4.html

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"All the Earth, all the time, live and in color": That's the pitch for a new infotainment company called AstroVision, based in Alexandria, Virginia, which has announced plans to place a webcam in geosynchronous orbit 22,000 miles above Earth. Unlike weather satellites, which usually provide one black-and-white image every 15 minutes, AstroVision (www.astrovis.com) will deliver a live, nearly continuous, true-color, super-hi-res feed of natural events such as volcanic eruptions, snowstorms, hurricanes, tornadoes, and large forest fires. Night promises to yield even more drama than day, with views of lightning borne on the tops of clouds and multikiloton-level air bursts from meteorites burning up in the stratosphere. "There is always something dramatic happening somewhere on the globe," says company founder and chief technical officer Malcolm LeCompte. "In space exploration, a pretty picture is far more than a pretty picture. It's loaded with information."

LeCompte started pitching his idea 10 years ago, leaving behind an academic career at Harvard studying the atmospheric chemistry of other planets. In July, he raised $5 million in first-round funding by convincing investors that the same people who consistently put the Weather Channel's Web site in Media Metrix's top 50 would also watch an Earthcam. The satellite itself is fairly simple, a suite of four high-definition CCD cameras - one wide-field and three targetable narrow-field units - coupled with a 320-Mbps, 8-GHz X-band downlink that will produce one frame every four seconds. Putting the satellite into orbit, however, will cost about $50 million, necessitating a second round of funding this fall.

If all goes as planned, the first bird will be aloft by the fall of 2002, and global coverage from a ring of five AVStar satellites will commence by mid-2004. LeCompte hopes the effort will not only be profitable but also increase the public's environmental awareness. "We'll be able to see what's going on in the rain forest, both the burning and the scars in full color," says LeCompte. "When people see the brown earth against the green of the forest canopy, 'slash-and-burn' will take on a whole new meaning."

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http://www-news.uchicago.edu/releases/03/030128.ancientroads.shtml

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http://groups.msn.com/SpaceSatelliteSensing/aerialphotographyandsatelliteimagery.msnw