Map Information

This nowCOAST™ time-enabled map service provides maps depicting visible, water vapor, shortwave infrared, and longwave infrared imagery composited from various geostationary satellites orbiting the globe. Global coverage is provided for the visible, shortwave infrared, and longwave infrared products from the NOAA/NESDIS Global Mosaic of Geostationary Satellite Imagery (GMGSI) product, which composites together imagery from Meteosat satellites, the Himawari-8 satellite, and GOES satellites every 3 hours at 8km resolution. Higher spatial and temporal resolution is provided for the Western Hemisphere from the GOES-EAST and GOES-WEST satellites. The horizontal resolution of the GOES visible composite images are 0.5km while that of the GOES shortwave infrared, longwave infrared, and water vapor composite images are approximately 2km. The GOES-EAST and GOES-WEST composite imagery each update on 15-minute intervals. The GOES-EAST and GOES-WEST composites are mosaicked together in one map layer per channel (e.g., GOES-EAST Visible and GOES-WEST Visible are combined in a single GOES Visible layer). The GMGSI composites are contained in three additional layers (one per GMGSI channel). The visible imagery indicates cloud cover and ice and snow cover. The shortwave, or mid-infrared, indicates cloud cover and fog at night. The longwave, or thermal infrared, depicts cloud cover and land/sea temperature patterns. The water vapor imagery indicates the amount of water vapor contained in the mid to upper levels of the troposphere, with the darker grays indicating drier air and the brighter grays/whites indicating more saturated air. The nowCOAST™ map service is updated with new GOES-EAST and GOES-WEST composite images every 15 minutes, and with new GMGSI composite images every 3 hours. For more detailed information about layer update frequency and timing, please reference the nowCOAST™ Dataset Update Schedule.

Background Information

The GOES map layers display visible (VIS), shortwave infrared (SIR), longwave infrared (LIR), and water vapor (WV) imagery from the United States' NOAA/National Environmental Satellite, Data, and Information Service (NESDIS) Geostationary Satellites (GOES-East and GOES-West). The GMGSI map layers display visible (VIS), shortwave infrared (SIR), and longwave infrared (LIR) imagery composited from several geostationary satellites orbiting the globe, including the GOES-East and GOES-West Satellites operated by U.S. NOAA/NESDIS, the Meteosat-10 satellite, one of the Meteosat Second Generation (MSG) series of satellites operated by European Organization for the Exploitation of Meteorological Satellites (EUMETSAT), and the Himawari-8 satellite operated by the Japan Meteorological Agency (JMA). These satellites circle the Earth in a geosynchronous orbit (i.e. orbit the Earth at a speed matching the rotation of the Earth). This allows the satellites to hover continuously over one position on the surface. The geosynchronous plane is about 35,800 km (22,300 miles) above the Earth, which is high enough to allow the satellites a full-disc view of the Earth. GOES-East is positioned at 75 deg W longitude over the equator. GOES-West is located at 135 deg W longitude over the equator. The two satellites cover an area from approximately 29 deg W to 180 deg W. The images are derived from data from GOES' Imagers. An imager is a multichannel instrument that senses radiant energy and reflected solar energy from the Earth's surface and atmosphere. The Visible, Shortwave Infrared, Water Vapor, and Longwave Infrared images are obtained from GOES Imager Channels 2, 7, 8, and 14, respectively. The Meteosat-10 satellite is located at 0 deg E longitude to cover Europe and Africa. The Himawari-8 satellite is located at 140.7 deg E longitude to cover the Asia-Oceania region. Both the GOES and GMGSI raster images are obtained from NESDIS in Network Common Data Format (NetCDF).

Time Information

This map service is time-enabled, meaning that each individual layer contains time-varying data and can be utilized by clients capable of making map requests that include a time component.

In addition to ArcGIS Server REST access, time-enabled OGC WMS 1.3.0 access is also provided by this service.

This particular service can be queried with or without the use of a time component. If the time parameter is specified in a request, the data or imagery most relevant to the provided time value, if any, will be returned. If the time parameter is not specified in a request, the latest data or imagery valid for the present system time will be returned to the client. If the time parameter is not specified and no data or imagery is available for the present time, no data will be returned.

This service is configured with time coverage support, meaning that the service will always return the most relevant available data, if any, to the specified time value. For example, if the service contains data valid today at 12:00 and 12:10 UTC, but a map request specifies a time value of today at 12:07 UTC, the data valid at 12:10 UTC will be returned to the user. This behavior allows more flexibility for users, especially when displaying multiple time-enabled layers together despite slight differences in temporal resolution or update frequency.

When interacting with this time-enabled service, only a single instantaneous time value should be specified in each request. If instead a time range is specified in a request (i.e. separate start time and end time values are given), the data returned may be different than what was intended.

Care must be taken to ensure the time value specified in each request falls within the current time coverage of the service. Because this service is frequently updated as new data becomes available, the user must periodically determine the service's time extent. However, due to software limitations, the time extent of the service and map layers as advertised by ArcGIS Server does not always provide the most up-to-date start and end times of available data. Instead, users have three options for determining the latest time extent of the service:

1. Issue a returnUpdates=true request (ArcGIS REST protocol only) for an individual layer or for the service itself, which will return the current start and end times of available data, in epoch time format (milliseconds since 00:00 January 1, 1970). To see an example, click on the "Return Updates" link at the bottom of the REST Service page under "Supported Operations". Refer to the ArcGIS REST API Map Service Documentation for more information.
2. Issue an Identify (ArcGIS REST) or GetFeatureInfo (WMS) request against the proper layer corresponding with the target dataset. For raster data, this would be the "Image Footprints with Time Attributes" layer in the same group as the target "Image" layer being displayed. For vector (point, line, or polygon) data, the target layer can be queried directly. In either case, the attributes returned for the matching raster(s) or vector feature(s) will include the following:
   • validtime: Valid timestamp.
   • starttime: Display start time.
   • endtime: Display end time.
   • reftime: Reference time (sometimes referred to as issuance time, cycle time, or initialization time).
   • projmins: Number of minutes from reference time to valid time.
   • desigreftime: Designated reference time; used as a common reference time for all items when individual reference times do not match.
   • desigprojmins: Number of minutes from designated reference time to valid time.
3. Query the nowCOAST™ LayerInfo web service, which has been created to provide additional information about each data layer in a service, including a list of all available "time stops" (i.e. "valid times"), individual timestamps, or the valid time of a layer's latest available data (i.e. "Product Time"). For more information about the LayerInfo web service, including examples of various types of requests, refer to the nowCOAST™ LayerInfo Help Documentation

References

• NOAA, 2013: Geostationary Operational Environmental Satellites (GOES). (Available at http://www.ospo.noaa.gov/Operations/GOES/index.html).
• A Basic Introduction to Water Vapor Imagery. (Available at http://cimss.ssec.wisc.edu/goes/misc/wv/wv_intro.html).
• CIMSS, 1996: Water Vapor Imagery Tutorial (Available at http://cimss.ssec.wisc.edu/goes/misc/wv/).