Near-surface remote sensing with fixed timelapse cameras

Astron is embracing the high-tech low-cost future for environmental monitoring by developing automated timelapse camera systems. Cameras installed in fixed locations (timelapse systems) represent a tool for vegetation monitoring and general site surveillance (Figure 1). When sites are within range of the mobile phone network, imagery can be acquired without the need to send staff to the field. Timelapse systems are an ideal complement to aerial and satellite remote sensing monitoring.

Figure 1: Timelapse camera system with remote download capability installed for vegetation monitoring in the Pilbara.

A time series of imagery from a fixed point greatly facilitates the observation of environmental dynamics: for example, plant growth, recruitment, weed cover changes, grazing pressure, erosion and flooding. When the time series of images are stitched together as a video, fine scale dynamics are readily observable in a matter of minutes. Subtle changes at sites can be observed from such videos that would likely be overlooked in records and photographs gathered by field staff.

Here at Astron we are especially focused on developing timelapse systems for quantitative monitoring of vegetation health. By measuring greenness, timelapse systems have been used to track seasonal cycles in vegetation condition (for example, Ide and Oguma 2010). Using standard cameras (red-green-blue capability) and image processing software, quantitative monitoring of vegetation in a variety of settings is possible: groundwater drawdown zones, discharge and reinjection sites, surface flow shadows, reserves, vineyards and plantation forestry. With a sufficient time series of imagery, control charts can be developed to simplify the identification of trends in greenness that signify a potential problem.

Astron is extending the power of timelapse cameras for vegetation monitoring by incorporating near infrared (NIR) capability. With NIR, we are able to more sensitively detect changes in vegetation health; healthy plants reflect NIR light more strongly than unhealthy plants and other objects. With NIR and visible light measured, timelapse videos of the commonly used index for vegetation health, Normalised Difference Vegetation Index (NDVI), can be produced. Statistics for NDVI can then be extracted for regions of interest over time to chart changes in vegetation health (Figure 2). The video below shows NDVI across a short period of the day using a camera setup outside the Astron office for demonstration purposes.

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Figure 2: Demonstration of quantitative monitoring using NDVI; a) sample areas of interest and b) values extracted on a minute by minute basis for these areas from a portion of the video.

While aerial and satellite remote sensing systems have the clear advantage of spatial coverage, timelapse cameras have the clear edge on temporal coverage; combining the two approaches addresses both space and time. The high temporal resolution of timelapse systems is especially important for sites with high conservation or economic values where impacts could occur between intervals of programmed site visits or airborne or satellite image captures. The ability to detect early indications of a problem at a site assists with timely and effective management intervention, for example, the application of irrigation to drought stressed vegetation prior to irreversible drought damage.

Timelapse camera systems are now an obvious choice for inclusion in vegetation monitoring programs that aim to be low cost yet sensitive with quantitative measures that detect changes early. We are continuing to develop our capability with timelapse systems and look forward to assisting our clients to harness the technology. 

To talk to us more about using customised timelapse camera systems for environmental monitoring contact Rob Archibald on (08) 9421 9600 or email us using the contact form.