Introduction

Raw and processed data sets from RU-COOL hosted glider deployments are accessible via ERDDAP. ERDDAP provides users with the ability to query, plot and download either the entire data set or a subset of the data set in a variety of common formats.

There are 3 versions available for each deployment:

Ideally, each of these 3 versions will be made available for both real-time and delayed-mode operations. Real-time data sets are typically lower resolution that are usually decimated to allow for efficient transmission to shore. Delayed-mode data sets are high resolution and contain the entire data set, but are only available after the glider has been recovered.

The following are detailed descriptions of each data set type and the differences between each type as well as the ERDDAP server used to host the data set type.

Raw Trajectories

Raw trajectory data sets are served on the RU-COOL ERDDAP server. The ERDDAP data set IDs for these data sets begin with the deployment name and end with -trajectory-raw-rt or -trajectory-raw-delayed respectively, depending on whether the data set is a real-time (rt) or (delayed) data set.

Trajectory data sets are best thought of as a time series of glider observations through 4 dimensions (time, depth, latitude, longitude). These data sets are NetCDF versions of the raw data files stored by the glider and contain all available observations, whether the glider is drifting on the surface or diving and climbing through the water column. With the exception of the following variables:

  • time
  • depth
  • latitude
  • longitude
  • platform
  • source_file
  • trajectory
  • pressure

The variable names in these data sets are the same as they are in the original [demnst]bd files. These data sets are primarily used by glider pilots and operators to monitor or analyze flight characteristics of the glider.

Science Profiles

Science profile data sets are served on the RU-COOL ERDDAP server. The ERDDAP data set IDs for these data sets begin with the deployment name and end with -profile-sci-rt or -profile-sci-delayed respectively, depending on whether the data set is a real-time (rt) or (delayed) data set.

Science profile data sets are a series of profiles contiaining glider observations through 4 dimensions (time, depth, latitude, longitude). An observation must be recorded during a vertical profile of the glider. As such, any observations that are not part of an indexed profile (i.e.: drifting on the surface) are not included in these data sets. These data sets also contain variable attributes that describe the parameters according to CF conventions as well as a number of other community governed conventions (IOOS, ACDD, NCEI and NERC).

Science profile data sets also contain derived parameters (not directly measured by the glider), variables that are renamed from their original glider names to more familiar names and a set of QARTOD QC flag variables containing the results of a series of QC algorithms run on each profile. While these data sets are very similiar to those found in IOOS National Glider Data Assembly Center, there are differences between them for the following variables:

  • time: the specific timestamp for an observation
  • latitude: the (interpolated) latitude for an observation
  • longitude: the (interpolated) longitude for an observation
  • profile_lat: the mean (center) latitude for an entire profile
  • profile_lon: the mean (center) longitude for an entire profile
  • profile_time: the mean (center) timestamp for an entire profile
  • profile_id: the mean (center) timestamp for an entire profile that uniquely identifies the profile

QARTOD quality control algorithms are also run on these data sets (on an individual profile basis) and the results are stored in variables containing *_qartod_*. The minimum and maximum values used for these tests are determined by RU-COOL staff. All original obserations/values are not removed or corrected. Instead, they are flagged according to the results of the QC algorithm and it is incumbent on the user to remove vaues that they deem incorrect.

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IOOS National Glider Data Assembly Center

IOOS National Glider Data Assembly Center (NGDAC) data sets are served on the IOOS Glider Data ERDDAP server. The ERDDAP data set IDs for these data sets contain only the deployment name for real-time data sets or end with -delayed if the data set is delayed-mode (after the glider has been recovered).

These data sets are very similiar to the RU-COOL Science Profiles data sets, with a few exceptions regarding variables:

  • time: the mean (center) timestamp for an entire profile This variable is the same as the profile_time RU-COOL Science profiles variable.
  • latitude: the mean (center) latitude for an entire profile. This variable is the same as the profile_lat RU-COOL Science profiles variable.
  • longitude: the mean (center) longitude for an entire profile profile_lon RU-COOL Science profiles variable.
  • precise_time: the specific timestamp for an observation
  • precise_lat: the specific (interpolated) latitude for an observation
  • precise_lon: the specific (interpolated) longitude for an observation
  • profile_id: an integer uniquely identifying the profile and all obseravations that were measured during that profile.

QARTOD quality control algorithms are also run on these data sets (on an individual profile basis) and the results are stored in variables containing qartod_*. These tests are run by the NGDAC and minimum and maximum values used for these tests are determined by the NGDAC staff. All original obserations/values are not removed or corrected. Instead, they are flagged according to the results of the QC algorithm and it is incumbent on the user to remove vaues that they deem incorrect.