STREAM User Guide

[LAADS - william.wainwright]

Hello! This page will serve to provide guides and examples on how to use the various features of the STREAM website located at https://ladsweb.modaps.eosdis.nasa.gov/stream/. You can also find a video guide that covers most of the information below here: https://www.youtube.com/watch?v=7849z4fzC6o

Finding the right image
Several website functions rely on you converting your regions of interest to Copernicus Sentinel-2 tile identifications (IDs) or USGS WRS2 Landsat Row/Path. If you are unfamiliar with these terminologies, we have linked a tool on the website specifically for that purpose. On the tile coverage page, denoted by the calendar icon on the top navbar , there is a link to an eatlas.org page. This page is preconfigured to show overlays for the tiling grids for both Sentinel-2 and Landsat 8/9. Enable whichever grid you are interested in and navigate to your area of interest on the map. We recommend noting which cells your water body falls into for future reference. Generally, when searching for Sentinel-2 tiles via STREAM or our Application Programming Interface (API), it is recommended to include the leading ‘T’ as an identifier (e.g., T18SUJ). When entering a Landsat Row/Path, write it as a 6-digit number with leading zeroes where necessary. For example, if the map shows a lake at “33 16”, its RowPath identifier would be 033016. This page then displays the dates for which that tile is viewable on the interactive map.

Using the map viewer - CURRENTLY NOT WORKING FOR MOST SCENES
STREAM has an interactive map for viewing the product maps for supported sites all at once and with adjustable color-scaling. The base layer of the map is Google satellite imagery , rendered in OpenLayers . By interacting with the controls on the right-hand panel, you can add a product layer to the map. Selecting the satellite, product type, year, month, and day are all necessary before hitting the “Set Layer” button. Panning and zooming on the map will cause more tiles to load, and it may take a few seconds depending on current traffic.

Once a layer is loaded, you can adjust the color mapping applied to it via the dual-end slider bar. This feature is particularly useful as it allows you to interpret the data more effectively. The minimum and maximum values are used to anchor the edges of the color map to product values. Any product value outside of the set minimum and maximum will display the same as the closest value within the bounds. For example, a chlorophyll (Chla) map with the slider set to 10-40 will show a range of colors representing chlorophyll values between 10 and 40. Chla values below 10 will be the same color as 10 (blue), and values above 40 will be the same color as 40 (red). When changing the position of the sliders, it may be necessary to pan the map slightly to cause the colors to update.

When a product layer is visible, a readout of the value at the current pixel will also be visible. The approximate Latitude and Longitude for that pixel are also given to assist with comparison to in situ data or as a point of reference for where to look in the full product GeoTIFF maps. As the web map comprises many images at different zoom levels, more precise readouts may be obtained at more zoomed-in views of the region of interest. Pixels filtered out during our processing, mainly due to cloud cover or sunglint, may appear as gaps or holes in the displayed images. These gaps can cause unusual visual artifacts at certain zoom levels depending on the geometry.
The map tools on the right-hand side also have settings for the scale bar, allowing you to change the units and the bar type.

Accessing the web archive
The archive page of STREAM hosts the GeoTIFF copy of the product maps. These images are geo-referenced and have a resolution of 30 meters per pixel. To download product images, you can navigate the directory structure from the base /archive/ page. The first folder level is the year of observation, and the second is the day of the year. After selecting both, the final page will list the files available for download that were observed on that date. The naming convention for these files is based on the original scene identifier for the Level-1 data but contains information about the product and processing version . Separate columns identify the scene ID and product for ease of reading. Clicking the product name will redirect to a direct download for the product, and an expected file size is given for validation.

Using the API
STREAM also has a RESTful API. We hope to include a step by step guide to using this API in the near future, but for now a full OpenAPI 3.0 documentation of our API can be found at https://ladsweb.modaps.eosdis.nasa.gov/stream/api

[philliec1]

We are trying to use the new STREAM. Can you suggest a tile that does work so we can at least experience the features of STREAM?

[LAADS - william.wainwright]

Hello! We are still working to fix a technical issue to make tiles appear on the web map properly at all zoom levels. That said, you should find that some tiles are now appearing in the tile search results. I would suggest looking at Chesapeake Bay, sentinel tiles T18SUJ and adjacent.

[dwhited]

HI, I am interested in obtaining secchi depth data for lakes in British Columbia and Alaska. Ideally we would like a mean from July 1 to August 31st of each year, but would take daily data if that is the easiest solution. Also in a dream world, we would also like estimates from landsat 5 and landsat 7. I believe Nima hinted at this, that it might be possible to derive those estimates from earlier missions. I have attached a pdf of our general area of interest. Some of the lakes are quite small. Thank you for any help in this endeavor.

[johnedaki]

Hello, which geospatial software is suitable for the analysis of chlorophyll geotiff file?

[dwhited]

Hi, we would either use the output in R or ArcGIS software. And we are interested in secchi depth output. Thank you.