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Plan for Extensive Measurements in the Canals of Venice
The ability to accurately and continuously collect large quantities of data in the Venice canals would be beneficial to our sponsors because it would allow them to better monitor the canals' hydrodynamic behavior, and in turn better understand their existing characteristics. The data can contribute to more informed decisions regarding canal maintenance, and can be used to confirm hydrodynamic modeling of the inner canals. The use of high-precision instruments is ideal for collecting accurate data - however, the cost and amount of experienced man-power required to use them across the city is high.
Our goal was to investigate reliable but inexpensive ways to collect measurements. The two devices we built and tested were the Floating GPS Device, for measuring current velocity and direction, and the Tide Level Measuring Stick Device, for measuring water levels. Our final goal of this plan was to make all the information available on Venipedia.
Floating GPS Device:
A GPS-capable smart phone enclosed in a water-tight PVC capsule running the Android/Google app My Tracks
This device runs the My Tracks app while floating down a canal. It tracks the position that it’s in using the GPS in the phone. The app also tracks how long it is running to calculate the average velocity the device was moving. We compared this device with the past IQP "float-and-blade" measuring device to assess its accuracy. We found that the data outputted by the app requires correcting for the track to represent the actual path travelled by the device, making velocity measurements from this device somewhat inconsistent. However, the device is effective at depicting the direction that the current is moving; if several devices could be released into many canals simultaneously, the overall flow through the canals at a given time would be represented.
The PVC capsule cost approximately 15 euros to make, and the smartphone purchased in Venice cost 150 euros. Future developments of the device could possibly reduce the cost of a GPS device.
Top Left: GPS capable smart phone that runs the MyTracks app while inside a PVC capsule in the Venetian canals. Top Right: original track produced by MyTracks app; recorded when device had been released from a boat (Bottom) at the green marker during outgoing tide in Cannaregio
Left: Water-tight, floating capsule for housing the phone. Constructed from PVC pipe and painted fluorescent colors for visibility in the water. Right: Diagram of phone/capsule setup in water
Tide Level Measuring Stick Device
In order to measure the relative water level (relative to known sidewalk heights) within the canals of Venice, a measuring stick has been constructed. The stick is placed vertically in the water and photographed; the photos are later analyzed to determine the water level in the canal at the time the photo was taken. This device was placed in key locations and several canal measurements were taken easily and in a small amount of time. Water level data collected with the device was compared to the actual tide levels recorded at the Misericordia tide gauge - through this comparison, we were able to determine that the measuring stick method collects very accurate measurements.
This method was also very easy and quick to execute in the field. The photos took only minutes to take and we could move on to other measurement locations efficiently. The ability to collect measurements quickly is ideal for point-to-point comparisons because reducing time between measurements in different locations reduces factors such as wind and tides, which change constantly with time and impact canal hydrodynamics. Additionally, the device only cost approximately 10 euros to construct in Venice.
In the future, the sticks could be further developed to be stationary devices in several canals and could be incorporated into a citizen science effort. Essentially, people could take pictures of the sticks and upload them through an app. Such an app could determine the water level and record the water level, the time the picture was taken, and its location.
Photographs of the measuring stick in the water are taken (left) and each photo (right) is analyzed to determine the water level in the canal at the time of the photo. The measuring stick is placed in a location with a known sidewalk height relative to the 1897 Punta della Salute zero point (obtained from Insula) and the number of centimeter increments is counted from the sidewalk edge to the surface of the water to calculate the water level
Left: Graphic showing water levels collected using the measuring stick in Cannaregio around the forecasted time for high tide. Right: Comparison of data collected with the measuring stick (during a full tide cycle) for one canal segment, versus actual water levels collected at Misericordia tide gauge on the same day
Design:
The measuring stick that was constructed in Venice is made from a length of white fiberglass that is 2 meters long, 3 centimeters wide and approximately 2 millimeters thick. The strip's material is flexible but resistant to salt water. Centimeter-wide black stripes were spray-painted at 1-cm intervals, and every 4 centimeters the pattern alternates between black-and-white stripes and black-and-color stripes.
This color pattern and increment design was intended to allow water level readings to have centimeter accuracy. In the case that the photo from which the water level is being taken is difficult to read (due to poor photo quality or far distance from the stick), the alternating colors will allow an approximation of within 4 centimeters.
Venipedia Pages
All of the information and data collected throughout this project will be made available to the world through Venipedia. Venipedia is a wiki-based website that focuses on sharing information about the city of Venice. A template for individual canal pages will be created and then populated with the data collected throughout the project; these pages also include a map showing the location of the canal and general statistics about the canal. An example individual canal page can be found here. Another information page that was updated includes the Canal Hydrodynamics page, which provides a history of past hydrodynamic studies conducted in Venice, and discusses factors that affect the inner canals of the city.
The CSV file for uploading to CK Console can be found here
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