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Frequently Asked Questions

The information below provides our best answers to the most frequently asked questions about MODIS Land validation activities.

If you have additional questions, please mail to Jeff Morisette
(return to MODLAND validation page)
(go to MODLAND page)

Answers to MODLAND Validation FAQ

Jeffrey T. Morisette, Jeffrey L. Privette, Chris Justice
 

Why are there not more Core Sites?

Because the EOS Core Site Network is a pioneering effort, its development has required a significant amount of coordination and activity among EOS instrument teams, DAACs, validation scientists, science networks and field site personnel.  Thus, we sought to keep the network of manageable size (initially 24 sites worldwide) until we have a proven operational system.  We are also tightly constrained by financial, personnel and equipment resources.  Nevertheless, the Core Sites are firmly established, and ground-measurement activities and data protocols are in place.  Combined with the non-core sites, the Network should provide sufficient validation data for the initial year of Terra land validation.
 

Why are there so few core sites outside the US/North America?

U.S. sites are generally the most familiar to and cost effective for most EOS/NASA investigators.  In addition, since existing site networks most closely associated with NASA and pre-launch activities are in the U.S. (e.g., the U.S. LTER network and the BOREAS and FIFE sites), their use allows significant resource leveraging.  However, other major biomes around the world are represented.  While the international sites are more sparse, these locations will provide procedural and protocol development for regional EOS activities.  Within a year of launch, additional international sites and site networks can be incorporated into EOS validation activities.
 

How big is a 'site'?

The nominal EOS Validation Core site extends +/-100 km from its center coordinates (corresponding to a science tower or other key feature).  For logistical purposes, any measurement or activity within this area will be associated with the site.  Thus, there may be multiple measurement locations and land cover types at "one" Core Site.
 

What is expected from a Core Site?

A Core Site is expected to maintain some data collect infrastructure (such as an instrument tower), accessibility for validation field campaigns, and reasonably stable land use.  We encourage field data collectors to register all ground data with the Oak Ridge National Lab Mercury system
 

Must a core site have a tower?

No.  An instrument tower is not required and some of the Core Sites do not have towers. However, many sites do have towers either in place or planned.  Towers can greatly facilitate the ongoing measurements of some parameters, such as landscape-level reflectance and CO2 or energy fluxes, which are EOS Terra products.
 

Must bigfoot sampling be used?

The BigFoot program has developed a sampling procedure meant to characterize the landscape surrounding a flux tower.  While it is not essential for all validation campaigns to follow BigFoot's sampling scheme, certain elements of their procedure are important.
  • The sampling should cover a large enough area to relate to a small block of MODIS pixels.  At 1-km pixels, this implies that sampling should cover an area from 5 to 10 km on a side.
  • Due to anisotropy in the landscape (some examples are given in the Jeff Morisette. 
     

    Are instruments available if I supply field personnel?

    MODLAND has some field instrumentation (such as LAI-2000s, albedometers, hand-held digital NDVI cameras and ceptometers).  They are generally available on loan, however the borrower must be willing to share the resulting data with MODLAND investigators.  An agreement on data use and rights may be recommended in such cases. For more information contact for Jeff Morisette.
     

    Will MODLAND buy equipment?

    MODLAND generally will not purchase validation equipment for non-MODIS investigators or sites, however its equipment can be borrowed (see above). 
     

    If I agree to share my field data with EOS investigators, how quickly is it needed?

    If the field activity is funded by the EOS Validation Program, the data must be made available to the science community within six months of data collection.  For field activities not sponsored by that Program, it is of course the data collectors' choice.  However, because the entire science community and general public benefit from a rapid and accurate validation of EOS satellites and products, we urge field personnel to contact EOS instrument teams and consider rapid data sharing.
     

    If I agree to share my field data, must I register it with the Mercury data system?  Can access to my data in Mercury be limited?

    Using the Mercury system  to register field data is strongly encouraged.  The Mercury system has been developed to include an easy-to-use metadata creation tool.  This tool can be helpful to any investigator wishing to create metadata for their fieldwork - even if just for their own records.  The Mercury system also allows the user to maintain the data locally and to, during initial QA or revisions, "hide" the data from the Mercury search and query harvester.  This allows the investigator ultimate control of any data they register with Mercury.
     

    If I wish to join in EOS validation, must I work at a Core Site?

    Most quality field data can be used to validate a related EOS product.  However, when investigators are flexible about locations, we urge them to consider working at a Core Site (or with data from a Core Site) since those sites will be the most EOS data rich in the early post-launch time frame.  This will provide the most opportunity for multiple data comparisons, scaling, and leveraged investigations.
     
     

    Can my site be added as a Core Site?

    Additional sites will be considered for inclusion as Core Sites soon after launch.  Investigators wishing to nominate a site should contact Jeff Morisette or a MODLAND PI.  A major goal of the Core Sites is to gather enough data and focus initial validation activity so to establish validation protocols and procedures; which, in turn can then be implemented to a far greater number of sites, which themselves may not be "Core Sites".  The primary considerations of adding a site to the "Core Site" list are that the site:
    • fills a need with respect to biome type, 
    • is integrated with some other network (such as Fluxnet, AERONET,...), 
    • has a long-term history and committment, 
    • has a site contact committed to maintaining communication with MODLAND/NASA, and 
    • has field data collections that can be make available within a resonable time (~6 months)

    If I agree to share data with EOS validation, how often must I collect data?

    Optimal data collection frequency depends on the parameter being characterized and the method and objective of the validation effort.  Researchers are urged to contact the EOS PI(s) in charge of relevant product(s) for guidance.
     
     

    If I wish to contribute to the EOS validation effort, much I conduct the comparisons of my data with the corresponding EOS products?

    This responsibility ultimately falls on the EOS instrument teams and validation investigators.  They are most familiar with the EOS algorithms and products.   However, those individuals cannot conduct all of the studies required for comprehensive global validation of all EOS products.  Moreover, independent field investigators may be most knowledgable about the sites, conditions, and the field data sets.  Therefore, in most cases, collaborative efforts between independent data collectors and EOS investigators may be most beneficial to the programs' objectives.
     

    What are opportunities to participate in SAFARI 2000?

    SAFARI 2000 (Southern African Regional Science Initiative 2000) is an umbrella-like coordinating activity for land-atmosphere research in southern Africa.  It is open to any investigator wishing to join.  Participation in SAFARI increases opportunities for resource leveraging (e.g., NASA ER-2 flights), data and information exchange, and community activities (e.g., simultaneous sampling of very large areas).  It can also facilitate access to or support from the region.  Because its Intensive Field Campaigns are occurring very soon after Terra's launch, SAFARI provides an excellent foundation on which to validate and use EOS products.  Interested investigators should consult the SAFARI WWW page.
     

    Who will maintain www sites for the Core Sites?

    MODLAND maintains a WWW page for each Core Site.  The Core Site pages provide an overview of the site (including site coordinates and vegetation characteristics), descriptions of and access to available data, and links to related WWW locations.  Investigators working at a given site are encouraged to maintain a more detailed WWW site and coordinate with MODLAND so the web sites are complementary rather than redundant.
 

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phone: (301) 614-6676

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Responsible NASA official: Dr. Jeffrey T. Morisette, Code 923, Goddard Space Flight Center

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