Category: Charts

Shaded Relief - Sediment Charts

2011 Jan 10

With the BETT series including some ‘new’ dams this year, it is going to even the playing field out when it comes to ‘local knowledge’. I am going to try and give you a ‘leg up’ on how to get ahead of the field using some tools that are available to us today.

First and foremost is Google Earth, try identify ‘unique’ areas from the satellite imagery and create waypoints using the Placemark Tool of the Points of Interest, or POI’s.




Tip:
Remember to create a folder FIRST, and in this case name it Woodstock Dam for example. Keep all Paths, Placemarks and Image Overlays in this folder.




The next step is to get a sediment map of the area, available from Department of Water Affairs and Forestry.

Tip:
Try getting a digital copy, this will save you the hassle of converting the paper chart yourself.

Now you can overlay each section of the dam into GE (Google Earth), and calibrate it.

Tip:
Use easily identifiable objects such as roads wherever possible to ‘calibrate’ your overlay image accurately. Don’t rely on a shoreline because it is nearly impossible to know for sure where the shoreline is from the charts. You don’t necessarily have to do this for all the chart sections, as in this case there are 16 sections, just identify the areas you want to fish and do those.

Once you are done doing this you can start ‘fine tuning’ your POI list. Let’s take this GE image for example, and try identifying which of these three channels could be possible ‘bass highways’:-




From the satellite photo channels 1 and 2 look really good with sharp defined edges. But channel 3 looks a bit ‘weak’ and not that great.

But once you overlay the sediment chart you see that channel 1 is worth trying and channel 2 is totally useless because it just flattens out to nothing as it enters the water. But channel 3 is now the #1 POI in this area as it has a defined ridge all the way out to near the centre of the bay, making it a first class bass highway. You will still need to confirm this with your sonar though, and if it is still well defined look for some isolated cover (timber, rocks etc) along the edges using your SideScan. And finally use your 50/200kHz conventional sonar and 800kHz DownScan to identify possible fish in the area.



Identifying POI's:-