Survey of the Limit of the High Tide of Theodosia InletSurvey of the Limit of the High Tide of Theodosia Inlet

INTRODUCTIONINTRODUCTION

Underhill Geomatics Ltd was contracted by Public Works and Government Services Canada to conduct a Land Act survey of the Toquana IR #4 North of Powell River, for the transfer of the lands from Canada Lands jurisdiction to BC land titles jurisdiction. Part of the boundary of the original reserve was the limit of “high tide of the Theodosia Inlet” around the outlet from the Theodosia River. The resultant Plan EPC1446 was surveyed in the late fall of 2015 by Mr. Christopher de Haan, CLS, BCLS.

BACKGROUNDBACKGROUND

The Theodosia River empties into Theodosia Inlet in an estuary consisting of numerous islands separated by some deep and not so deep channels. Since the limit of the high tide is only discernable on the ground during a short temporal period each day (semi-diurnal tide), it was found that the walking of the limits of the islands and channels was not possible before the water receded and the limit was no longer discernable. We needed to find a different solution for the survey.

CONCLUSIONCONCLUSION Underhill Geomatics Ltd has been conducting aerial photography surveys using an unmanned aerial vehicle, (UAV), for a number of years-mostly for topographic and volume surveys. Here we used the technology to fly our UAV over the estuary (approximately 1 square kilometre) and obtain more than 800 photographs covering the entire estuary within one half hour each side of high tide. At the same time, the elevation of the highest of the tide was measured. The photographs were processed using Agisoft photo processing software using more than a dozen targets. A DTM was created and the contour of the measured elevation (high tide) was used to delineate the limit of highest tide of the year in the estuary. This was checked in the field by observing the limit of the tide at various locations.