Howdie!

Welcome to the COG-Explorer!

This app allows you to visually inspect individual Cloud Optimized GeoTIFFs (COGs) like scenes from the Landsat-8 archive on Amazon S3. Either copy the URL to the COG or to the index.html of the Landsat 8 scene you want to investigate in the "Custom URL" field and hit "Load URL or sample", or alternatively, show one of the preselected samples using the button. Note, while optimizing the data access by utilizing the COG features to only retrieve necessary parts of the data this app downloads the actual raster values, UInt16 for Landsat 8, which uses quite some download bandwidth. Additionally the data is download in its original projection and re-projected on the fly.

The selected COG is displayed on the map, which you can zoom and pan as you like. It is visualized as natural color composite with some default processing steps applied. Using the button you can adjust the visualization by selecting the bands to use and processing steps to apply.

For the band selection, either define red, green, and blue channels individually or use one of the predefined scenarios. As image processing steps currently sigmoidal contrast enhancement and gamma can be applied on all or individual channels.

This app uses the geotiff.js library to read the actual raster values like UInt16 from the band files (or the overviews, depending on the maps zoomlevel). Taking advantage of the optimized structure of COGs, only the parts of the file that are actually required are requested, drastically reducing the overall amount of data transmitted from the archive.

Please keep in mind that at the moment this app is a proof-of-concept demonstration with some room for improvement. Nevertheless we're looking forward to hear your feedback. Also let us know if you want to help in any way.

If you want to know more about COGs please refer to their introduction page.

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