Nov 30, 2014 in Travels by
  • Prospecting surveying in Republic of Congo
  • Prospecting surveying in Republic of Congo

Hi, I have recently returned from surveying in the Republic of Congo. Another jungle filled two weeks. It is always special for me to spend time in the rain forests. We are involved in a Potash prospecting project situate North of Pointe Noire. The deposit is situated in a second growth forest that was intensely logged by the French in the Sixties. It is really amazing how it has recovered and returned to its natural state.

Two days ago I glimpsed Gorillas about 100m away as we crossed a clearing. We often see their tracks crossing the logging tracks but have only be lucky enough to see the briefest of glimpses twice. A few days earlier,  2 forest Elephant crossed one of the old logging roads as we were walking to survey a drill site. Not sure how they manage it but they seem to glide through the thickest of undergrowth, which I with a team of bush cutters take hours to move through.

The thickness and height of forests make GPS surveying very difficult. Even with a high poor transmitter the RTK signal can only penetrate 2 – 3km’s and we find a small clearing in forests we jack the GPS receiver up on a 5 m pole to improve of sky view.

Last year we completed a 240 Km traverse through the forest using traditional survey methods. We were surveying seismic stations at an 8 m interval.  Halfway through the task we switched to Robotic total stations. What a huge leap in productivity. Line of site along the logging roads is at best 200 meters. To meet the accuracy requirements we observed two arcs at each setup. Observation times went from 10 -15 minutes to 4 minutes due to target recognition and that after targets have been located on first round the robotic station automatically completes the arc and as many more arcs as required. Survey accuracies increased by 25%. The other biggest increase in productivity resulted from being able to mount the prism rod on a quad bike and auto track it as the driver moved from one seismic point to next.

For the drill hole collar surveys and check points on traverses we use 6 hour long fast static observations which we both post process and also check by using the Canadian Post processing services. Trimble has just announced a similar service which we tested our results against and it worked well. An advantage of the Trimble site for GPS post processing is that one does not first have to change observation files to Rinex format. The Trimble site is at is http://www.rtx-pp.com/.

The other sites are  Canadian site : http://www.geod.nrcan.gc.ca/online_data_e.php
Australian site http://www.ga.gov.au/earth-monitoring/geodesy/auspos-online-gps-processing-service.html