Presented at NZ Hydrological Society Technical Workshop 17-20 March 2020
Since attending the Wellington and Australian STIV workshops Environment Southland has trialed image velocimetry at two sites in Southland. So far results are looking promising, dependent on environmental conditions. Smartphones are used to capture video at both of these sites with Ku-STIV to process the video.
The first site is a temporary site at Bright Water Spring where a camera is positioned directly above a surveyed point with the ground control points visible in the frame. The height to the camera’s sensor is then recorded to calibrate the video.
The second site is installed alongside a hydrometric station on the Makarewa River. This site is a fixed camera setup where a smartphone can be located in a surveyed bracket. There has also been a drone flown to capture video. The surveyed bracket provides a fixed view of the ground control points while capturing video. Having the ground control points visible helps with the ortho-rectification process as different phones are added to the mount. A mount like this has potential citizen science applications, either for engagement or if a camera and data connection are cost prohibitive
Current issues that are experienced at the two sites are the distribution of texture (reach selection), wind combined with glare (camera position) and picking a suitable surface alpha coefficient.
Initially the plan was to use IP cameras, but some issues were encountered with the lower cost IP cameras. The focus then shifted to using smartphones, these provide a low cost setup with a suitable camera and network connection.
Future development using image velocimetry for Environment Southland involves using Automate, an Android app where tasks on the smartphone can be automated. The remote smartphone will be setup at the site in a weather tight box with a power supply. Automate allows configuring a smartphone to record video of determined length when the phone receives a command via SMS. Further commands allow media to be uploaded with the devices mobile data via FTP or Google Drive. The application can be configured to record media at a set time interval for sites where there is no network reception.
Michael McDonald is an Environmental Technical Officer currently employed by the Southland Regional Council.
Michael’s work includes a mixture environmental monitoring, his main interest is in hydrology. Recent work with image velocimetry has had Michael installing and trialling two sites in Southland.
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