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For example, the epoch of a capture from May 1, 2018 is ITRF2014(2018.329). With ITRF2014 being an earth-fixed datum(as opposed to plate-fixed datums such as GDA94 or NAD83), imagery aligned to ITRF are subject to continental drift. For example, in Australia the movement is 70mm per year and some parts of US move at about 14mm per year. In order to compensate for the continental drift, we provide plate-fixed projections through WMS and reverse the shift by a variable amount depending on the capture epoch. Those projections are based on either GDA94/GDA2020 (Australia) or NAD83(US). As a consequence, we encourage you to use one of the plate-fixed projections in order to minimise misalignment in your GIS application, especially using surveys captured years apart.

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An earlier generation of our camera systems captured data with captures with a GSD of 7.5cm (3”) vertical imagery with an absolute horizontal accuracy of 61.7cm (24.3”) RMSEr.

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