Author Topic: How I use my 981 for searching  (Read 16959 times)

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Offline Jolly Roger

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  • Joined: Mar 2009
  • Location: Germany, Lake Constance
  • Posts: 804
  • HB Addicted
  • Unit(s): HELIX 9 G3N, 998Cx SI, 959DI
  • Software: latest (mostly)
  • Accessories: AS GR50, custom towfish and: A boat!!
How I use my 981 for searching
« on: May 21, 2009, 04:10:56 PM »
Hi all,

I just write down how I use my 981 for searching and I hope that it helps others to get the same success as I had since I started. Two boats in just three weeks isn't a bad start I think, hehe.
Talking about three weeks: Although I got lucky with these first success in such a short time, I consider myself as a beginner and I would be glad if you would share your "technique" with us and tell us how you do your hunting.

I have an "old" 981 and this is hooked up to an as well "old" GARMIN Streetpilot III. For sure I'd like a 1197 for its bigger screen and resolution, but this has to wait until the global finance crisis is over, hehehe. Using the outdated STREETPILOT has a reason as well: It has a better screen size than my old GPS III plus, a colour screen and I have the possibility to upload a decent map of Lake Constance. And: ---> global finance crisis  :)
So far for the hardware.

The first boat was actually a walk in the park, because I had the information that there was a boat missing and got the rough location, where it was suspected to be. As I already wrote, I had the boat located within 30 minutes, but didn't recognize it due to my lack of experience how to interpret the picture on the screen.
By chance I met a fisherman a day later, who told me that he had lost one net in this area. It got caught by something on the ground and he wasn't able to recover it. So he bundled it up neatly, cut the swimmers off and just dropped it where it got caught. He took me to this location and I was amazed that this was more or less the same spot where I had my "first contact" on day one.

A bit smarter and, thanks to the advice from guys here on the forum, a bit better prepared with the settings of the unit, I started to search the area again.

Here's what I did and do when I drive out for exploring the hood:

First I create a waypoint, right at the spot which I got shown from the fisherman.

If I have a rough location to start from, the next thing I do is laying a trolling grid over the waypoint and set it to a 50 metres width by using the zoom function while in Nav. Mode. Then I start to drive a search pattern using the trolling grid as a reference.

If I just stumble over a target like I did with the second boat, I don't use the trolling grid step.

The depth in this area is around 20 metres so I set the SI range to 50 metres.
The graph speed to 4, boat speed around 6 - 8 Km/h.

When I get something on the screen, I take a snapshot and place the cursor on the "target".
Next I turn around and follow the steering instructions given by the 981. As soon as I close in on the target to 30 metres, I delete the cursor from the screen and watch it.

As soon as the target starts showing up on the screen, I create a waypoint on the STREETPILOT.
By doing this, I can use the STREETPILOT for navigation and homing in on the target from different angles. I still can use the full screen of the 981 for SI or 2D observation at the same time. One can use the split screen (SI/NAV), but would be limited in the details.

Next is doing a couple of runs directly over the target from different angles, watching it in downlooking mode in both 50 kHz and 200kHz to get a "feeling" for the height of the target. If necessary I alter the waypoint on the STREETPILOT.
After that I do some passes in SI mode from different directions beside the target varying the distances. My experience by now is that distance for turning around for the next run is at least 100 metres. This gives enough time to alter course and set up the boat for the next pass without falling in panic and hectic.
On the SI runs I take my time and do a separate record from every run. These records I view in YellowFin and DeepView at home and measure height, change the colours etc. Very usefull to determine if the target is worth a dive  :).

I think reviewing the records and snapshots on the computer is essential, because one can see more details and it helps a lot to interpret the records/pictures.

I also download the track and waypoints from the GPS to compare and refere where I saw what.
I'm not used to the GOOGLE EARTH function in HBPC, therefore I prefer to work with my QUO VADIS navigation software.

So, that's it for now. Let me know what you think about it and if you have suggestions to perform better: Shoot!!!

Happy hunting and fat booty!

« Last Edit: May 22, 2009, 08:00:12 AM by Jolly Roger »

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