## 2 Materials and Methods
### GLIDER Data Management Platform  
To manage the data collected by the gliders, a data management platform \"GLIDER\" was developed by the Norwegian Research Centre (NORCE), Kongsberg Digital (KDI), and the Norwegian Institute for Water Research (NIVA). The platform was designed to perform quality control through a range of tests, ensuring high-quality data access to researchers and end-users. The data management platform provides continuous tracking of autonomous measurement platforms during surveys with real-time access to time series of measured data (e.g., temperature, salinity, conductivity, and fluorescence). The gliders send time-series data via satellite links (Figure 3). The solution for storing the time series is based on the Kognifai digital ecosystem provided by KDI. The solution consists of an asset database in addition to the time-series database. The metadata for the gliders, instruments, and sensors are stored in the asset database [59].  
The GLIDER web portal implements interactive visual analysis and covisualization of large multidimensional datasets for exploration of the collected data, giving scientists access to the data stored in these databases. The portal was implemented by adapting Enlighten-web, a web application developed by NORCE, and supports interactive visual analysis and covisualization of large multidimensional datasets. Predefined plots were prepared to follow the data acquisition in real-time and to see a quick overview of the data. Users can easily create and store their own plots for further analysis. Brushing and linking [60] functionality is provided for exploring complex datasets, to discover correlations and interesting properties hidden in the data (Figure 4). Enlighten-web offers interactive performance in brushing and linking on large datasets by utilizing the graphic processing unit on the user's computer. Several filters can then be combined using Boolean \"AND\" operators.  
The GLIDER web portal also supports Web Map Services (WMS). This allows the web portal users to contextualize observations by adding map layers from external services, e.g., representing meteorological and oceanographic data.  
During a survey, NIVA servers monitor the Kognifai database time series and automatically perform quality control (QC) services. The QC services collect the new data added to the database and perform a set of regionally dependent QC tests. A flag indicating the quality of each data point is written back to the database. The QC tests and algorithms follow the International Copernicus.eu standard [61]. The web portal provides an option to filter and view only good-quality data flagged during the QC process.  
Due to bandwidth and cost limitations, echo sounder and hydrophone data were not transmitted to the time series database via satellite link but stored on-board the gliders. These data files were retrieved at the end of the survey and uploaded to Microsoft Azure Blob Storage. Through the brushing and linking functionality, the GLIDER portal supports selecting relevant bulk data for download, which can be readily incorporated into models. For example, MET Norway uses hydrographic data provided by the gliders for near-real-time assimilation in their ocean model [59].  
Figure 3: Overview of the e-infrastructure implemented in the GLIDER project. The gliders send time-series data via satellite links, which are stored in the Kognifai digital ecosystem. Here, servers at Niva automatically perform data quality control and the data are available through a web portal. The NorShelf ocean model also assimilates data, improving ocean predictions. Satellite links are a potential communication resource not used in their presented work due to high costs.