Streamlit: COG Visualization

Web app for visualizing and labeling COGs.

Setup

1. If GDAL libraries are not on the system, conda is the simplest way to install them:

$ conda env create -f streamlit-cogs.yml

• If GDAL libraries are available, skip to step (3), but it's a good idea to create a virtual environment:

$ python -m venv venv && source vevn/bin/activate # on Unix

2. Activate the newly created environment:

$ conda activate streamlit_cogs

3. From inside the directory that includes the pyproject.toml file:

$ python -m pip install .

Server Usage

$ streamlit run streamlit-cogs/main.py

Running and Deployment

• If run locally, this may open the browser at the URL:port given, otherwise a network URL is given if it is reachable.
• For actual deployment options, Streamlit apps are easily dockerizable, or for more public apps, they can be deployed straight to Streamlit Community Cloud through GitHub.

Web App Usage

• Choose from the preloaded imagery, grouped together by date (All), or select an individual layer only.
  • Layers can also be toggled on and off from the map view by clicking on the top right button.
• Adding URLs: Other COG URLs may also be added manually in the appropriate text input box; separate by a | if adding multiple. Make sure to click Submit changes to load the new URLs.
• Band ordering: Depending on the COG, the bands may be out of order, so they can be reordered using the multi-select box, and clicking Submit changes. It's also possible to inspect one or two bands individually by only including the ones needed.
• Rescaling: To change the contrast levels of the displayed bands, they can be rescaled in the Band rescaling section. The default values are preloaded with the COG metadata min/max values. After the appropriate band min/max values are edited, click Rescale bands to add the bands as layers to the map view.
• Labeling: The map view provides multiple labeling tools on the left-hand side. Clicking a drawn object on the map will open a popup of its GeoJSON object representation, while clicking on the Export button in the top right downloads a GeoJSON file with all the drawn objects.