In Part I we studied the user manual word for word, and this is the best advice anybody can give when it comes to StructureMap.

In this Part II I would like to mention some of my own experiences and tweaks.

Structure Options:-

1. Range
a. I found that a range of 120ft is about best for 455kHz.
2. Transparency
a. I like my transparency set to ‘Min’ because as you increase transparency, you lose image contrast making it difficult to spot points of interest. (POI’s)
b. If you find something interesting but want to check the depth from the background contour charts, then you can either increase the transparency, or simply turn the Structure Overlay off, then back on.
3. Pallette
a. Either Blue (9) or Greyscale (2) for me
4. Contrast
a. 40% is about the best average, but I do increase it a bit for smaller POI’s.
5. Frequency
a. ALWAYS 455kHz when logging data for your StructureMap. This gives you a much greater range and more information for your maps.
b. Once the log has been converted to a map, and you are on ‘Saved’ mode, then I suggest going back to 800kHz.
6. Noise Rejection
a. On – the last thing you want on your map is interference.


1. Pages –
a. Chart full screen is a must – the bigger the better when logging. You can maximize your viewing area further by turning on the Auto Hide Softkeys for the HDS8 and 10.
b. When viewing in saved mode I suggest Structure (down) + Sonar (50kHz) + Chart. Once again – such a pity that the engineers at Lowrance didn’t make a 3 way vertical page split for this.
2. Chart Settings -
a. Range Rings – On. This helps you to know how far things are from your current position, and to maintain equal distance between passes when logging parallel lines.
b. Heading Extension – On. This helps you line up with approaching POI’s
3. Overlay Data – On. I suggest the following:-
a. COG – Course over ground helps you maintain course when running parallel lines. (Add 180° when doing return pass)
b. Position Error – Watch this like a hawk when logging, because if your EPE (estimated position error) deteriorates dramatically while logging for a map, your map will be inaccurate.
c. Depth – you don’t want to run aground while logging.


1. I use an external GPS receiver mounted as close to my StructureScan transducer as possible.
a. Without this you will continually have to compensate for the distance from your transom to the console.
b. Should your return pass overlap too much, the distance from transducer to GPS receiver will now be doubled and the POI will be averaged out completely, and in most cases – simply disappear.
2. An iPilot for the Minn Kota Terrova and RipTide helps tremendously when making tight turns, maintaining course and positioning the boat perfectly while logging.
a. I leave the Trolling motor in the water while idling along on the main motor while logging, and only use it when I need to.

In Part III we look at actual logging techniques and boat control to get the most out of your Lowrance HDS Gen2 StructureMap feature.