FAQs

Got a question about the DAAC? Never fear, your answer might be here! If it isn't, feel free to reach out to us at lpdaac@usgs.gov 

ASTER

Is there a fee associated with ordering ASTER data?

No. Effective April 1, 2016, all data products distributed by the LP DAAC are available for public distribution at no charge.


What ASTER data products require an order to be placed?

All ASTER data, aside from the Precision Terrain Corrected (AST_L1T) and expedited data (AST_L1AE, AST_L1BE) require an order to be placed as the product will be made on-demand. This includes: radiance data (AST_09, AST_09T, AST_09XT, AST_L1B, AST_14OTH), elevation data (AST14 DEM, AST14DEM), emissivity data (AST_05,), temperature data (AST_08), reflectance data (AST_07, AST_07XT), and unprocessed data (AST_L1A). In addition, ASTER GDEM (ASTGTM) version 2 has special policy agreements that are required before downloading the data. These data can be ordered using NASA's Earthdata Search.

Can anyone submit a request to acquire new ASTER data over a specific location?

Requests for ASTER acquisitions can be submitted by approved users through the Data Acquisition Request (DAR) tool. More information on how to apply to be an approved user is available through the NASA JPL ASTER website.

Why are the corners clipped for some AST_L1T VNIR only scenes?

These clipped corners are due to errors, such as band offsets or projection of boundary data outside of the scene frame.

Why is there not an AST_L1T scene for every AST_L1A granule?

ASTER Precision Terrain Corrected scenes are not produced if any of the bands in an AST_L1A granule fail during resampling. This typically occurs due to errors in the AST_L1A geolocation arrays. Additionally, since AST_L1T scenes are processed using AST_L1B processing algorithms, AST_L1T scenes are not available when there are any band failures in an AST_L1B granule. Finally, a band in a AST_L1T scene may not be available if the telescope related to the band was not requested to be turned on during acquisition.

How can I tell if a scene is terrain or precision corrected?

This information can be found in the ASTER Precision Terrain Corrected (AST_L1T) metadata, under the field "CorrectionAchieved". This field will be populated with the level of correction (Terrain+Precision, Terrain+Systematic, Systematic, or Precision) obtained for the scene.

What is the difference between terrain and precision correction?

Terrain correction removes geometric errors associated with observing a ground location from an off-nadir angle. AST_L1T scenes that do not have Digital Elevation Model (DEM) available will not have terrian correction, these scenes are typically over open ocean and small islands. Precision correction removes the geometric errors due to imprecise knowledge of the satellite's location and velocity (or ephemeris), it's behavior, (yaw, pitch or roll), and the detector acquisition information. Precision correction is completed when 20 or more ground reference points can be matched to an equivalent region in an ASTER Precision Terrain Corrected (AST_L1T) scene. If these locations can not be matched the scene will not be precision corrected, this may be due to clouds in the region, a dark scene (potentially a scene captured at night), the angle of the sun and shadows in the scene, or the scene is a thermal infrared (TIR) scene. If a scene is not precision terrain corrected it will have systematic correction, similar to a north-up AST_L1B scene. For more information please read the AST_L1T Quick Guide.


What is the difference between ASTER GDEM Versions 1, 2 and 3?

The first version of the ASTER GDEM, released in June 2009, was generated using stereo-pair images collected by the ASTER instrument aboard Terra. ASTER GDEM coverage spans from 83 degrees north latitude to 83 degrees south, encompassing 99 percent of Earth's landmass.

The ASTER GDEM V2 added 260,000 additional stereo-pairs, improving coverage and reducing the occurrence of artifacts. The refined production algorithm provided improved spatial resolution, increased horizontal and vertical accuracy, and superior water body coverage and detection.

ASTER GDEM V3 will add another 360,000 additional stereo-pairs.

MODIS

Why do I get some unexpectedly large or hard to interpret data values when I am working with MODIS data?

Most MODIS Science Data Set (SDS) layers are in 8-bit or 16-bit format. This requires a scaling factor to be applied. For information on the scale factor of a specific band for a specific product, please see the corresponding DOI landing. DOI landing pages can be access via the MODIS Products Table. More information on the scaling factor is available by watching the Part 2s of the MODIS Version 6 Data at NASA's LP DAAC videos on YouTube.


How can I interpret the MODIS Quality data layers?

The majority of the MODIS land products contain quality layers. Each layer contains a lot of information about the quality information associated with each individual pixel in the scene. To aid in file size management, this data has been packed in bit format. The LP DAAC offers several tools to aid in unpacking the bits and interpreting the quality information. The Application for Extracting and Exploring Analysis Ready Samples (AppEEARS) allows users to view and interact with quality information for a variety of products before they download the data. The ArcGIS MODIS Python Toolbox provides users with a simple and intuitive way to decode and interact with quality layers for previously downloaded MODIS products using ArcGIS. More information on interpreting the quality information and using these tools is available by watching the Part 3s of the MODIS Version 6 Data at NASA's LP DAAC on videos YouTube.


Why do some MODIS data not extend beyond March 2017?

Occasionally MODIS data are reprocessed to provide updates to make previous data even more accurate and to create new data products. Recently MODIS data were reprocessed from Version 5 data to Version 6. Version 5 data are now in the process of being retired. Part of this process included the ceasing of forward processing on March 31, 2017. MODIS Version 5 data will be available for download until April 9, 2018. After this date the data will officially be retired and no longer distributed by the LP DAAC. Visit the LP DAAC MODIS Products Table to see the available MODIS Version 6 data products and to access their individual DOI landing pages. Each DOI landing page will describe the improvements to that specific data product and how it differs between Version 5 and Version 6.

Data Access

How can I bulk download data distributed by the LP DAAC?

Bulk download options are available from DAAC2Disk as a script that can be downloaded and executed from the command line. Also, data are available from the LP DAAC Data Pool via HTTPS. Please ensure you have authorized your download method for your Earthdata login account. To accomplish this, log in to your account from the Earthdata Login page, and click on “ Authorized Apps” under "Applications" in the title bar. You will be presented with a list of approved applications. At the bottom of the list click the “Approve More Applications” button. Type in “LP DAAC Data Pool” in the text box and hit enter. In the application search results click the checkbox next to “LP DAAC Data Pool” and then click the “Approve” button. You should be returned to the approved applications page with a green confirmation bar acknowledging your request. Be sure to update your scripts to allow for logging in to your Earthdata login account.

Where is my data order notification?

Typically you will receive a notification that your order was submitted within a few minutes. However, if your order was placed more than 3 days ago and you still have not received a notification from us, please check your spam folder. Also, please add "lpdaac@usgs.gov" to your list of trusted senders to prevent notifications from going to Spam folder in the future. If you have checked your Spam folder and did not receive a notification, please contact LP DAAC User Services at lpdaac@usgs.gov.


What is an Earthdata account and how can I create one?

A Earthdata Login account provides a single access point for user registration and profile to manage all EOSDIS system components (DAACs, Tools, and Services). Your Earthdata Login account helps the EOSDIS program understand how users are using EOSDIS services and this aids in helping improve the user experience through improvements to tool customization and services. The Earthdata Login account is available at no charge to the user and provides open access to EOSDIS data free of charge.

Data Citation and Reuse

How do I cite my data?

Each DOI Landing Page provides a citation generator that will automatically create a citation for you based on the data product you are using. The DOI Landing Pages can be found under the search data catalog.


Am I allowed to reuse LP DAAC data?

All data distributed by the LP DAAC contain no restrictions on the data reuse.