Rio Tinto Inhambane Estuary Survey
Bathymetric surveys of 3 separate study areas in the Inhambane estuary for the Rio Tinto Jangamo mining operation.
The survey of 3 separate study areas of the estuary channels derived from aerial mapping so as to determine the depth of these channels and see if a vessel could gain access to the open sea from certain land points. This information would be used to navigate the channels as we had calculated x sections every 100m apart and would sail on these lines taking readings at 20m intervals at right angles to the channel direction.
Survey control :
We were able to source the bench marks in Inhambane from the INAHINA authorities in Maputo and so our task once on site was to locate these points and then to check and verify the stations. We were able to find 2 primary stations namely the point SH MN1-1980 next to the Instituto National da Marinha building and the point MN3-2011 located at the entrance to the Catedral da Nossa Senhora de Inhambane. These points were then tied to an old brass bench mark CM11-1951 located on the pavement near to the Inhambane jetty as we had surveyed and fixed the horizontal position of this mark previously and now we precise levelled the new point in using the above 2 primary bench marks. These bench marks were to be then our elevation control for this project and are based on the Inhambane chart datum Zero which is 1,93m below mean sea level .M.S.L.
Survey equipment :
The survey was conducted using a survey grade Trimble R.T.K real time Kinematic G.P.S system with the survey base set up on the bench mark CM11-1951 which is situated on the pavement near to the Inhambane jetty. This was the main base station and we checked onto 4 other bench marks using the Trimble 5800 rover receivers.
We were also able to set up the ski boat that was to accommodate the survey personnel, survey receiver and the Hydrolite echo sounder to undertake this survey . The surveys were down loaded into Trimble business centre T.B.C and processed using the templates for echo sounding, the results were stored in a csv format, which can then be read into our Model maker cad package for further manipulation.
Boat Authorisations .
We have the boat registered in Mozambique and for the Maputo harbour and so with the help of the Rio Tinto team and letters to the correct authorities namely the “Adminsitraco Maritima de Inhambane” we were able to secure a letter and permit to navigate on the Inhambane estuary. Further to this we also had to secure permission from CFM “Portos E Caminhos de Ferro de Mocambique “to gain access onto the jetty.
Survey data handover .
The survey data will be handed over with all the raw data as surveyed in the field in a csv file format, further to this we have also processed the data into contours to show the different elevations in the channel and this information can then be viewed in Google earth and ties up nicely with the sand banks and deeper channels. The data will also be handed over in a dwg format for further manipulation and or design work.