How Can I Obtain a Number of Years' Worth of Data

CLASS does not limit the amount of data requested by a user. We only request that our users limit the number or data sets ordered to less than 500 a day. If you can satisfy your data needs by using the CLASS Web Interface, please do so.

However, we understand that there are some data requests for which use of the interface is impractical due to the amount of data needed. For these requests, it may be possible for CLASS to offer an offline solution. To explore this possibility, please send us email at info@class.noaa.gov identifying your data needs, your affiliation, and your intended use for the data. We will forward this information to the appropriate authorities for consideration. Please keep in mind that, because this service is time and labor intensive, there is a waiting list which may delay processing of your request. In many cases, you may be able to retrieve your data faster by using the CLASS Web Interface.

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I Am Having Problems FTPing My Data

The CLASS FTP server is a Unix machine. The files stored in your FTP area are actually Unix links to files stored in other locations. Some Windows programs and Web Browsers mistakenly identify Unix links as directories and not as files. In most cases, you will be able to download the files anyway. However, in some cases, your FTP software will try to download the contents of the link.

If you are using an FTP program that does not follow the link but simply downloads it, please attempt the following:

Look for a newer version of the same program since later versions often will follow links.

Look at your configuration values for the program. Some programs have configuration options that allow the following of links.

Try using the FTP program provided with Windows.

Open a DOS window

Change to the directory in which you want your data placed.

Follow the FTP instructions CLASS sent to you in the Order Notification email.

Send us an email at info@class.noaa.gov with the name and version of the program. It is possible that we have already heard about your particular difficulty and thus could help you.

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I Cannot Connect to CLASS’s FTP Server

This is usually a network problem. If you have been able to connect to our FTP server in the past, please try again after waiting for 15 minutes. If the problem persists, ensure that neither you nor your network administrators have made any changes to your network or firewall definitions.

If the problem continues, or if this is the first time that you have tried to connect to our site, send us an email at info@class.noaa.govwith the following information:

Date and time (GMT) of your attempt to connect.

The IP address or hostname that you were using to connect to us. If you do not know this information, the name of your Internet Service Provider (ISP) should suffice.

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How Can I Read the Data That I Just Obtained From Your Site?

The files you obtain from CLASS hold what basically amounts to raw satellite data in specific formats. As such, the data needs special software for processing. If you are searching for ready to use images (GIF, TIFF, JPEG, etc.), you are not likely in the right place. Please visit NOAA’s home page for a list of sites that offer ready to use images.

If you are looking for data provided by CLASS, you have two options. You can write your own software by referring to the appropriate documentation. A good starting point is the Data Available section of our help pages. Alternatively, you can use one of the many commercially available viewing software packages. A small sample is provided elsewhere in this document.

CLASS users can download some JPEG images by doing a non-global spatial search of AVHRR data. Browse images of the overlap between each data set and the user’s search region are provided as part of the details for each hit. However, these images are mainly intended to help the user determine if they wish to order the given data set. Additional information on browse images is available here.

Additionally, the products section of our site allows users to download GIF images of Sea Surface Temperatures and a small number of other satellite derived products.

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When Are Data From New Satellites Made Available?

CLASS is scheduled to receive and distribute data from all NOAA POES satellites and from all DOD DMSP satellites. However, data from newly launched satellites are not initially considered operational. As such, the data are not available to the general public. CLASS makes the data available as soon as they are declared operational.

If you believe you have a legitimate need for pre-operational data, please email us at info@class.noaa.gov with your affiliation and a brief statement explaining your needs for the pre-operational data. We will forward your request to the appropriate authorities for consideration.

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I Am Already a CLASS User But Have Forgotten My Password

Using the same email address that you used to register as a CLASS user, please send us email at info@class.noaa.gov with the following subject "Account Information for User ID." If your password is on record, you will soon receive an email with your CLASS user id and password.

If you do not have access to the email address that you used to register the first time, simply register again.

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I Need My Data Delivered on Computer Compatible Media

As part of the mission of NOAA's Office of Satellite Data Processing and Distribution (OSDPD), CLASS provides electronic distribution of polar orbiting satellite data and data products. We understand that some customers prefer receiving data on computer compatible media, such as tapes or cartridges. CLASS does not provide data on tape. This distribution mode is supported through our partnership with the National Climatic Data Center (NCDC), NOAA’s long-term data archive. NCDC provides data on computer compatible media on a cost-recovery basis. Arrangements for tape distribution must be made in advance with NCDC’s Satellite Services Group at ncdc.satorder@noaa.gov.

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Please Explain the Spatial Search

CLASS's spatial search detects not only the hits for which the subsatellite path (nadir) intersects your defined search region but also those in which the overlap between the given data set and your search region is only on the limb.

Since many of the hits may have only partial coverage, we recommend examination of the coverage of each hit to determine which ones meet your needs.

The following two examples are cases of such partial coverage:

The search greatly improves the determination of the overlap between the search area and the individual hit. See example below. Note that CLASS's data extraction for subsetted data gives you each and every scan that intersects your search region.

The search better determines the boundaries of the browse images and accurately matches the browse images with the indicated overlap area. The search also improves the accuracy of the estimation of the size of ordered data sets.

The new algorithm shows significant improvement in its polar search capabilities. Searches near a pole do not yet detect all non-nadir hits, but this issue will be addressed in an upcoming release.

In the past, some users would artificially increase their search areas to try to capture non-nadir hits. This expansion is no longer necessary. You should simply specify your true area of interest.

This robust search may be somewhat slower than the previous search. However, we believe its increased capabilities and reliability more than makes up for the usually modest increase in search times. Future releases will aim to improve the search speed.

Note that the spatial search described above does not apply to SAR data. A separate search algorithm is used for SAR data.

Please contact CLASS User Assistance if you have any questions or comments regarding the new geographic search algorithm or plans for further search improvements.

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Why Do I Receive Data Outside of My Search Area?

When you perform a spatial search and order subsetted data from CLASS, the data extraction system will produce a file containing each and every scan which intersects your defined search region. A scan will be included even if only a small portion touches your area and the entire scan will be included even if most of it is outside of the search region.

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My Extracted Data Doesn't Seem to Match My Search Area?

When a user requests geographic selection when ordering an entity, CLASS's data extraction software selects each and every scan which has any overlap with the user-defined region. Consecutive passes within a single global data set (4KM AVHRR) may intersect the user region. If this happens, the extracted data set will include those scans from the first pass followed immediately by the scans from the second pass. There will be nothing in the data set to indicate the end of the first intersecting region and the beginning of the next.

CLASS cannot attest to the ability of any of the Satellite Data Viewing Software to properly separate the two regions. The user should be aware that multiple regions may exist. This phenomenon is more prevalent for larger or more poleward user-defined regions.

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Where Can I Find Detailed Descriptions of the Format of the AVHRR, TOVS, and ATOVS Data?

Detailed information on the AVHRR and TOVS data types for satellites TIROS-N through NOAA-14 can be found in the NOAA Polar Orbiter Data User’s Guide at www2.ncdc.noaa.gov/docs/podug/

Details of the AVHRR and ATOVS data from satellites NOAA-15 and NOAA-16 can be found in the NOAA KLM User’s Guide at www2.ncdc.noaa.gov/docs/klm/

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Historic Information Processing of Data Sets

Current Status of Historic Information Processing of Data Sets at CLASS

Refer to our Data Documents here for details on becoming a RADARSAT user.

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Where do I find satellite and sensor status information?

Information regarding the status and condition of various satellites and sensors supported by CLASS is available at the following links. These sites may be useful in explaining problems you may be experiencing with some of your data.

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Satellite Data Viewing Software

The CLASS User Assistance Team receives many inquiries regarding the availability of visualization software packages for viewing data ordered from CLASS. There are many sources for packages that provide satellite remapping and analysis functions. The following are just a few of the organizations offering commercial packages or freeware to provide this capability. CLASS does not endorse any of the following packages or vendors.

Organizations or individuals whose software is not listed may have it included by contacting info@class.noaa.gov.

The following links are outside of the CLASS domain. You may wish to check their privacy policy.

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How can I use the Java Map?

The equidistant cylindrical flat map is a Java applet. You need to adjust your browser's configuration to allow Java applets. If your browser is configured to allow applets, the map will appear automatically.

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