VELMAP: Contributions Sought

So you've got some ice velocity data and you're wondering whether or how to contribute it to the community? Here are some considerations and guidelines related to contributing to VELMAP:

  1. Please contact us at braup@nsidc.org.
    After that, here is a general checklist of some things that we'll eventually need:

  2. Citation of Published Article
    We would like to be able to cite a publication about the data, no matter how obscure the journal.

  3. Description of Measurement Techniques
    Each dataset should have a detailed description of how the measurements were made. This descriptive text can usually be created from existing text from your publications. Alternatively, you could send us a rough draft with all the information in it, and we'll neaten it up for the web site.

  4. Error Sources
    The dominant sources of error should be identified. Possible examples include: uncertainty in survey pole tilt when top-of-pole measurement is made; GPS measurement uncertainties; uncertainty in determining peak in cross-correlation surface when comparing multitemporal satellite imagery.

  5. Error Estimates
    Estimates of uncertainty for each primary measurement should be given. If a set of measurements has one uncertainty that applies to all measurements in the set, then that can be stated in the descriptive text. Most velocities are computed from multitemporal position measurements; the time between measurements (and its uncertainty, if applicable) is also desired.

  6. Releasability
    A couple of investigators have sent us data with the request that we not make them public for a specified time. We can accept data from you and hold it in confidence, if you tell us how long this "proprietary period" will be in effect.

Other Considerations

  • Data Formats

    For datasets not derived from interferometric SAR, the final format of the distributed data will be a table consisting of point velocities (one per row), where the columns are

    Lat Long Speed Bearing Err_speed Err_bearing First_Date/Time 2nd_Date/Time Label/Station_Name Notes
    

    Other associated data are welcome (e.g. elevation, slope, etc). If your data are only position measurements, then we will gladly convert them to velocity data for you.

  • File Formats

    For small-to-medium sized datasets, the preferred format for files is plain ASCII text. If your data are in some proprietary format (such as a spreadsheet format), please export them to something such as "comma separated values" (CSV) or tab delimited text. Just about any quasi-systematic (or better) text format will do.

    If your dataset is large and in binary format, then please contact us (braup@nsidc.org) and let us know what you have.