Low-cost, Ultra-high Spatial Resolution Mapping of Intertidal Rock Platforms
Mitch Bryson · M. Johnson-Roberson · Richard Murphy
TL;DR
A kite-borne consumer camera and automated photogrammetry produce sub-centimeter 3D, colour maps of intertidal rock platforms cheaply, demonstrated at Cape Banks, Sydney.
BRIEF
Intertidal rock shores are usually studied by sampling small patches on foot. Satellite and aircraft imagery cover larger areas, but at coarse resolution or high cost for small ecology studies. This work builds a low-cost kite-mounted camera system and a photogrammetry pipeline that turns consumer-camera photos into 3D, photo-textured terrain models. The pipeline needs little human input and only a few ground control points. Maps at sub-centimeter resolution cover roughly 100 m at Cape Banks, Sydney, letting ecologists study algae and animal assemblages across scales.
Abstract
Intertidal ecosystems have primarily been studied using field-based sampling; remote sensing offers the ability to collect data over large areas in a snapshot of time which could compliment field-based sampling methods by extrapolating them into the wider spatial and temporal context. Conventional remote sensing tools (such as satellite and aircraft imaging) provide data at relatively course, sub-meter resolutions or with limited temporal resolutions and relatively high costs for small-scale environmental science and ecology studies. In this paper, we describe a low-cost, kite-based imaging system and photogrammetric pipeline that was developed for constructing highresolution, 3D, photo-realistic terrain models of intertidal rocky shores. The processing pipeline uses automatic image feature detection and matching, structure-from-motion and photo-textured terrain surface reconstruction algorithms that require minimal human input and only a small number of ground control points and allow the use of cheap, consumer-grade digital cameras. The resulting maps combine colour and topographic information at sub-centimeter resolutions over an area of approximately 100m, thus enabling spatial properties of the intertidal environment to be determined across a hierarchy of spatial scales. Results of the system are presented for an intertidal rock platform at Cape Banks, Sydney, Australia. Potential uses of this technique include mapping of plant (micro- and macro-algae) and animal (e.g. gastropods) assemblages at multiple spatial and temporal scales.