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TOPIC: Mapping and correct depth

Mapping and correct depth 6 years 3 months ago #5679

  • DiveExplorer
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When you are mapping do you often need to correct depth data which you have collected ?

It seems that every time when I go out and map then I need to manual correct depth later on. I only go for like 5 - 6 knots when I´m collecting data. I find my depth finder not accurate enough and sometimes fluctuation in depth numbers.
Humminbird 581i HD DI.
Mapping the ocean floor and search for history
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Mapping and correct depth 6 years 3 months ago #5680

  • Team Colibri
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Unless you map areas with large variations in depth, this is most likely a question of adjusting your ducer, or even better use a ducer with a narrow coneangle and adjust that correctly. ;) That said, I seldom do more then 4 knots when mapping as more speed means less quality, but with the right combination of boathull and ducer it is possible the get decent quality at higher speeds then that.
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Mapping and correct depth 6 years 3 months ago #5713

  • hermes
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Probably a daft question, but have you checked that your transducer is fixed correctly? I've got that t-shirt... The bolt had worked loose and the transducer was moving slightly - giving me some really odd depths as you can imagine!! If your depths are odd for the whole time, have you applied the correct tidal corrections (if surveying at sea). Is your transducer offset correct in rm? Might be worth doing a bar check (run the transducer over a known depth - ie use a tape measure to get the depth of a position in an area that's flat, then run over the position and compare after applying any transducer offset. Ive had good results at 5-6 knots, although I do a little post processing in rm to improve the final chart.
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Mapping and correct depth 6 years 2 months ago #5778

  • robm
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We also have to adjust tracks manually using Dr. Depth which is very annoying and time consuming, really hoping that Reefmaster's added feature to do this comes soon and represents and improvement over dr depth! For every 8 hrs of mapping we spend anywhere from 2-4 hrs of post-processing (i.e. correcting depths). We log data at 2-20 knots but speed doesn't seem to matter much, the structurescan transducer misinterprets the bottom at all speeds and all depth ranges. Shallow (<4m) areas with vegetation (weeds) and/or soft bottom are particularly problematic. I don't believe ducer placement or orientation is our issue but could be wrong.
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