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Interpreting Env-DATA results and FAQ

We hope that the Env-DATA System saves you many time-consuming steps in linking tracking data to environmental conditions, making it easier to test hypotheses and leaving you with more resources to design novel studies and collect high-quality data. Since we're certainly not the experts for every species, region, and environmental dataset, here's where your expertise comes in—putting the results in an interesting and realistic biological context. Here are some commonly asked questions about Env-DATA results to help:

How accurate are the results?

The annotated data are estimates that reflect the resolution and accuracy of the original datasets. Check the product source links for quality and accuracy information. Consider the temporal and spatial resolution of the environmental datasets as well as the tracking data, and consider what variability and trends are biologically meaningful. For example, weather conditions from global atmospheric models do not describe local conditions and so are only an approximation of what animals actually experienced. If the location estimates for your animals have an error of 1 km, annotating 30-m elevation land use in heterogeneous environments might not be useful. Also consider annotating related QC variables for products that provide them.

Where can I find the units, citation, and other information about my results?

The readme file in the zip file with your results provides units, definitions, original resolution, links to the source and terms of use, and other helpful information.

Why are my results a file with a header but no data?

The most common reason is that the user selected to annotate data for animals that have no associated locations. Make sure the data are uploaded and that they are correctly linked to animals using deployments. You can verify what data are deployed in the study by downloading the data or reference data (undeployed records are always at the bottom of the data file), viewing the data on the map, or comparing deployments and available data in the Deployment Manager. You can also choose to annotate data for tags rather than animals to include undeployed records.

Why do I have lots of "NaN" values in my results?

Nodata values ("NaN") are due to missing information in the original datasets requested, for example due to cloud cover when a satellite was overhead. You can get many NaN values when

  • The source file has periods or regions with nodata values, for example, if you request a vegetation index for a period when the animal was flying over the ocean, or sea surface temperature for a period when the animal was on land. For locations near the poles, remember that there are times of year when it will be nearly always dark and so there will be little or no satellite imagery.
  • The requested records fall outside the temporal or spatial range of the dataset: See our data products summary for the area and time covered by each product. For products that are available to the "present", there is a lag between today and when today's measurements are available as processed data files, so if you have live data feeds, the most recent few weeks will typically return NaNs for these products.

Solutions: See what obvious explanations there might be for your results as described above. You can also try requesting using a different interpolation method—as described in Env-DATA Interpolation Methods (look for "missing data"), nearest neighbour or inverse distance weighted interpolation will give a valid result even if some of the neighboring data values are missing, while bilinear interpolation will not. Some products include quality control variables that might indicate reasons for missing data.

How do I calculate wind speed and direction from the u and v wind?

A good resource with instructions that is recommended by NARR's support team is here. See the section on "geographic wind direction" and if you are using a spreadsheet program like Excel, see their warning under "two argument arctangent function" to make sure the equations work correctly.

Why do the timestamps look funny in Excel?

If you use Excel to view your results, be aware that it can corrupt timestamps and truncate values in the annotation results. See here to learn how to avoid this problem.

How do I cite information annotated using Env-DATA?

The animal movement and environmental information you annotate are not created or owned by Env-DATA or Movebank—always cite the original data providers when you present or publish your work. Many also want authors to send copies of work resulting from their products. Links to each environmental data provider's requested terms of use are in the readme file. For the tracking data, see the Citation and License Terms in the Movebank study.

How can I get more help?

If you receive an email saying or request has failed, have not gotten results within a few days, or have questions about the results not addressed above, please send the "access key" for the request to so we can take a closer look. This is in the third paragraph of the readme file, which can also be found by going to Env-DATA > Show My Requests and clicking on Details for the request, as shown here:

Movebank study name: Golden Eagles in Alaska
Annotated Animal IDs: 12345
Requested on Tue Oct 27 20:00:33 CET 2015
Access key: 5485945721593819135
Requested by: user name

For more details about how the Env-DATA Track Annotation Service works, see Dodge et al. 2013.