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HydroColor Test Run @ SF Bay

Join with the US Geological Survey, Nerds For Nature, and other naturalists and citizen scientists all around the Bay for a very exciting moment in participatory field research, and a perfect excuse for an early lunch break -- hey, it’s for science!


A common problem with remote sensing is ground-truthing, or making sure what the pretty images indicate actually corresponds to real facts at the earth’s surface. To support better water quality mapping through remote sensing by satellite, this project seeks bay-wide simultaneous data to validate algorithms developed by Thomas Leeuw (U. Maine) that map:

• Turbidity (NTU)

• Chlorophyll A (ChlA)

• Suspended Sediment Concentration (SSC)

This innovative use of ubiquitous technology for serious science research is being developed by the San Francisco Bay National Estuarine Research Reserve Education Program to support TSS mapping for a NASA-funded USGS-NERR project. They need help to document open-water surface reflectance at as many locations in the San Francisco Bay-Delta as possible during the Landsat8 overpass on July 24, 11:45 am.

The Hydrocolor app makes this possible by first calibrating the iPhone’s camera to a standard grayscale card, then asking the user to take a photo of both bay water and overhead sky. The app then converts these images to reflectance and irradiance data, which are saved as a text file that can be analyzed by researchers.

If you can, they would also like for you to collect a water sample in a small tube and return it to USGS for testing. Gravimetric analysis will be used to determine the actual sediment and organic matter in each sample, which will further help correlate remotely-sensed data to actual conditions.

Besides being a fun and interesting exercise in itself, future HydroColor outings will be based on what is learned from this trial run. Don’t miss this chance to make science history!


USGS is providing a free kit to help you participate. Contact Lisa Windham-Myers, Ph.D. (Research Biologist for U.S. Geological Survey) directly to make arrangements -- she can mail you the kit. You will get an autoreply that she is out of her office but she is working from home. Friday morning July 18 is the mailing deadline for you to receive it in time for the event.

If you have a choice, being on the water is best because you can both a) grab a sample (in the 500ml container provided) and b) point yourself in the right direction and avoid shadowing for the image.  If you're on a bridge, you will need to be on the "sun" side so that the  structure doesn't shade your water photo.

You will also need to download the Hydrocolor app from the iTunes store for $3 (sorry, no Android version yet). 

Keeping In Touch:

The whole point of the exercise is to spread out geographically as much as possible, so it won’t be one of our usual gatherings. But there are several ways we can still meet together virtually to share the fun. For one, please RSVP for this “virtual meetup page” for this event, so we can have an idea of who’s helping where, and so we can all stay connected and communicate up-to-the-minute details with each other in the comments section.

We’ll also be using the social media hashtag #hydrocolor to keep in touch on Twitter before, during, and after the sampling event. Share pics of your location and activities, or ask technical questions -- USGS and other experts will be on hand to help out.

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  • Kirk

    I recruited some colleagues from work and we got a sample at pier 14 in sf. The hydrocolor app worked well but you have to remember to hit "analyze data" before putting your phone away or the images are lost

    July 24, 2014

  • Lindsay I.

    No worries, Ken. I'm down at the docks in the lovely industrial Mission Bay. Getting stoked!

    July 24, 2014

  • Nature N.

    Hi all,

    So, so sorry but due to a series of unfortunate events I only last night received the sample kits for this project from Lisa at USGS. I am in southeast SF so if you still have time you can pick up your kit this morning here either at my home in outer Mission (975 Cayuga Ave) or at the local BART station (Balboa Park, email me kensanfran at gmail and I'll meet you there). Otherwise my apologies! We'll start further ahead next time when we do this again in the fall, better organized for sure.

    Some of you got your kits directly fro Lisa, so hopefully you all can still help with some results this time, let us know how it goes.


    July 24, 2014

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