Marsh pictures have been streaming since July 17, 2011 with generally great success and we have learned a lot about what it takes to send images from a totally remote place, located half an hour away from the first paved road. Images are streaming from the North River coastal marsh restoration project located near Beaufort, NC.
So, what does it take to have a GaugeCam system to measure water level in a stream?
First, it takes the camera that will do the trick of capturing pictures on a desired interval and of automatically sending the pictures to a server. Second, it takes power: good batteries and good large solar panels. Third, it takes a good white background with embedded fiducials. Fourth, it takes a stable camera mount.
First, the camera. The GaugeCam project and company would probably have remained at the stage of a great potential project, had we not discovered the Colorado Video company and its very good products. We are using a prototype of the Lookout V camera.
To be short, the camera has an embedded cell phone which sends pictures via a 3G card. So in essence, one needs 3G network coverage for this camera to work properly. We have experienced blackouts where the pictures do not go through. The first reason for that was that our (still small but that is about to change) server was full…
There also seems to be a somewhat erratic pattern of missing pictures between 22:00 and 02:00 at night. It seems to come and go and we have not been able to find a true reason on our side. We are thinking that it might result from the 3G network operator, although we have no actual data to prove this.
Second, the power system. We have a 55W solar panel to recharge two regular car batteries installed in parallel. Voltage has never gone below 12.4V. The marsh has no shade and is a great place for solar panels!
Third, the background. This is a critical part of the set up as it has to withstand the rigors of the field (sun, water, biological activities, etc.), remain flat and vertical. Actually, verticality is not necessary but it certainly helps to keep fouling to a minimum. The background that you see in the pictures is a film of plastic that has been laminated over a ½ inch think piece of Plexiglas by professionals. The background is attached to two posts that have braces to maintain verticality. It is essential that the background does not move! We will check regularly to verify that it does not!
Once the background is installed, it is important to measure the real world coordinates of the fiducials. This is really the critical part that all hydrologists and equipment installers have to do. Despite all efforts, it is our opinion that it is very difficult to make this measurement better than ±2 mm. This is particularly difficult in the marsh where the water level was changing all the time because of the tides. When the level hit the center of the lowest fiducial centers, water level was simultaneously measured above our reference value using a graduated ruler. All future measurements are then dependent upon that first call… Actually, other manual measurements will be done and if a bias towards over estimation or underestimation is detected, it will be taken as an offset to calibrate our instrument.
Fourth, it takes a good camera mount. This might end up being one of the most challenging task, especially in remote areas. Several options are possible: concrete, wooden or metal mounts… We abandoned concrete as it would not be desirable there for many reasons. We thought that metal would be very challenging because of varying moisture, salinity and temperatures. So we went for wood (see pictures). Braces were installed with the post to reduce vibrations from the wind. However, we have already noticed that images are looking more and more to the right as the whole mounting device is warping.
The camera itself is protected in an open wooden box which size has been reduced to a minimum to minimize wind effect.
We are learning a lot from this experience and are adjusting our software and hardware accordingly! We will keep you posted!