## 3 Implemented Results of Multi-Cloud Services
### Implemented Results  
Figures 5 and 6 illustrate the operational results of the utilization model presented in this study. The interface for processing ARD data and sharing settings in SaaS is shown in Figure 5. Step 1 in Figure 5 displays the screen for uploading KOMPSAT-3A bundled data. SaaS consists of a web mapping interface, and users can upload auxiliary files in Blue, Green, Red, Near Infrared, and Extensible Markup Language (XML) using the Data Adding function. Internal users perform ODC indexing for the stored bundled data to enable ODC utilization. The SaaS utilized in this study offers various internal/external satellite processing algorithms. It includes atmospheric and surface reflectance processing  
Figure 4: Sequence diagram for ODC indexing of KOMPSAT data in conjunction with public and private clouds.  
functions, as shown in Step 2 of Figure 5. The processed results are also visualized for each blue, green, red, and near infrared band, and ODC indexing is performed for the processed data, similar to the bundled data. Step 3 displays the indexed results via the ODC Explorer, which allows users to view data registered in the ODC on the web, including bundled images (KOMPSAT3A_Level-1G), atmospheric reflectance images (KOMPSAT3A_TOAR), and surface reflectance images (KOMPSAT3A_TOCR). By uploading and processing data in the private cloud, internal users can utilize this data via tools such as Jupyter Notebook. In Step 4, a data-sharing settings page is designed to make data available to external users as a public cloud service to external users. Users can choose to make uploading data (Data List) or processed data (Process List) public by setting the 'is public' option to 'On'. Once set, the data is copied to the public cloud service via an internal synchronization system.  
Figure 6 shows data synchronization to AWS S3 when the 'is public' option is set to 'On' in Step 4 of Figure 5. The synchronous system in the private cloud utilizes the S3 API to copy data, and selecting 'Off' deletes the data. The KOMPSAT-public bucket is created in the apnortheast-2 region of Amazon S3 to store KOMPSAT data. However, KOMPSAT data is not freely accessible, so only data managers have permission to access it through IAM, and the synchronous system proceeds with synchronization once authenticated. The Yet Another Markup Language (YAML) file required for ODC indexing is also synchronized during this process. Finally, synchronization involves copying the data to S3. Once completed, the synchronous system requests indexing processing from AWS ODC Core to add KOMPSAT data to the final public cloud ODC.  
Figure 7 displays the resulting process, where the synchronous system requests indexing from AWS ODC Core and Python S3 to DC on the AWS ODC Core virtual machine performs indexing. Figure 7 also confirms that the two TOC data sets that were set to public in the private cloud are served from the location of S3 (s3://kompsat-public (accessed on 26 June 2023)).  
Figure 5: Examples of the step processes on ODC and data sharing settings for private cloud KOMPSAT bundled data. Base map is OpenStreetMap [46] in Korean.