Q. How to do distance shooting in NaviPac. 3.10.5?
A. Distance shooting requires some special settings that are shown in the following screenshots.
NaviPac uses prediction algorithms to estimate when a point is reached.
- Go to NaviPac / Options / Global parameters / Filters, tick Deskew position.
Figure 1: Filters tab under Global parameters.
- In the Advanced tab, tick Use time for nav. Event definition as above to ensure that NaviPac performs a calculation related to the event.
Figure 2: Advanced tab under Global parameters.
- In the NaviPac Options / Event Settings
The object that controls the eventing must be a stable positioned object – and most often it will be based on the vessel CRP and not streamer or similar towed points.
Figure 3: NaviPac options with Event settings General tab.
Figure 4: Event settings with Distance events tab.
- If the shooting based on along-line travel or accumulated travel.
It is also important to consider the distance between points versus the speed, and as a rule of thumb you need more than 3 cycles between each shot. E.g. 6.25 meter and speed of 3 knots will be around 4 seconds between shot – which is just feasible. If not – then one way is to set NaviPac cycle time to e.g. 0.5 seconds.
- Set the trigger output.
NaviPac differs between the trigger (which happens when calculation is done) and the seismic output (the position of when it happened). That is why we normal see the use of the trigger output which leads to seismic fire:
Figure 5: Event settings with Trigger tab.
And then a second output happening shortly after with info on the shot.