6/29/2023 0 Comments Ground control pointsThe USGS Cal/Val team continually works to improve the quality of Landsat data. Details for each sensor are described below. When scenes fail to process to L1TP, the loss of the ability to use GCPs affect data from each sensor differently. How Geometric Errors affect Landsat Data Quality Visit the Collection 2 Tiers section on the Landsat Collection 2 page to learn more about Landsat Collection tiers. Each scene is placed into the appropriate tier, based on data quality and the level of processing. Landsat data are also characterized by Collection Tiers, which make up the inventory structure for Landsat Collections Level-1 data. Click here to see more details about L1GS. L1GS products are created when the locational accuracy is not sufficient to apply terrain correction, such as: Insufficient number of ground control points, such as small islands or Antarctic opaque clouds that obscure the ground or locational errors greater than the search distance for ground control. Click here to see more details about L1GT. L1GT products are created when the systematic product has consistent and sufficient locational accuracy to permit the application of a terrain model. Click here to see more details about L1TP. In these scenarios, a L1GT or a L1GS product will be created instead. Sensor issues include measurement/outliers in the spacecraft or instrument telemetry of an interval which also affect the usability of the GCPs. Scene issues include snow, ice, and clouds, which prevent an accurate registration of GCPs within a scene. In some cases (and more likely in older Landsat data), scene and/or sensor issues, or insufficient reference data can cause L1TP processing to fail. Precision and Terrain Correction (L1TP)Īll Landsat scenes are attempted to process to L1TP, using Ground Control Points (GCPs) and a digital elevation model (DEM).Landsat satellite data are processed into Level-1 scenes using the Landsat Product Generation System (LPGS). Each Landsat scene is processed to one of the three following processing levels:
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