Hydrographic Survey

We are developing a 33acre land in a flood prone area that requires an estimate fill of 400,000 cubic metres to bring up to road level as a mitigating factor and be classified as “Flood Free”.

The land is adjoining a river that meanders next to it and because the land is located at the end of the river, there is heavy sand and silt deposition, 2km up and down stream. Govt dredges the river every 5 to 8 years, funds permitting, and is currently conducting feasibility studies to allocate funds for dredging next year. Because we are considering dredging this material as preloading based on our Geotech reports we needed volumetric calculations to support our proposal to Govt to dredge at our cost and enter in to a funding agreement to be reimbursed when Govt’s budget come online this time next year. The Govt land surveyors have just surveyed and marked the river banks which are well within our profile mapping.

The objective is to determine the available volumes 2km up and down stream at 2, 3 and 4 metre depths. We have completed mapping the river and volumes from our 3D point cloud calculations indicate more than adequate volumes available if combined with other material. We have discounted the effect of dredge as well.

Our post processing Accuracy Report show all “0” Values for the RMSE, X, Y, Z for Otho @ 2cm/pixel.

GCP residuals are Total (RMSE) 2.0754cm 2.5033cm 3.0784cm

We have also done post processing on CAD Civil and Pix for comparisons. We use Trimble Catalyst and sub-meter corrections, Fiji land surveyors ground station correction services and the Fiji Grid Map EPSG.

I guess than the question here is how reliable/accurate are the volumetric stockpile calculations in DD for this purpose if we are to use it as a benchmark for a Govt proposal @ FJ$8.00 per cub for dredging.

We have been asked to undertake a similar project on an integrated resort, the above will influence our proposal.

Thank you…

What is your main objective? We currently have 2 construction projects underway that it was determined that a hydrographic survey would benefit the design. The topographic surveys that were used to design the projects were several years old and there had been quite a bit of erosion as well as water level rise. We already share the construction progress information with the engineer and now share a complete survey of the banks of the bodies of water.