NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: GPS vulnerable to hacker attacks
From: Peter Fogg
Date: 2010 Mar 27, 12:48 +1100
From: Peter Fogg
Date: 2010 Mar 27, 12:48 +1100
Jeremy writes:
Recently we were navigating around a series of lakes:
http://maps.google.com.au/maps?f=q&source=s_q&hl=en&geocode=&q=myall+lakes+nsw&sll=-25.335448,135.745076&sspn=42.067662,59.677734&ie=UTF8&hq=Myall+Lakes+National+Park&hnear=Myall+Lakes+National+Park,+New+South+Wales&ll=-32.449521,152.332993&spn=0.312317,0.466232&t=h&z=11
(if that long link is a problem, go to
http://maps.google.com.au/maps?hl=en&tab=wl
and enter: "myall lakes nsw" - then increase the magnification)
They're mostly shallow, but so was the draft of our houseboat. Nevertheless we had to navigate with care.
The water, particularly in the further lakes, is almost not salty at all, despite it being a system of sluggish flow and the sea not far, nearly fresh although this water looks like tea and tastes like tea because tea is what it is - vegetation-seeped.
We had a depth sounder which may have functioned just as it is supposed to, but there are extensive areas where 'seaweeds' (almost a monoculture of dense, mildly-prickly underwater bushes) grow almost to the surface and there, and even where they are a little underwater, the depth sounder signal seemed to bounce off a point somewhere deeper, where the growth was presumably thick enough to return it, although not off the bottom as indicated by the chart. It proved preferable to avoid these thick patches as much as possible, as at best they would greatly slow us down, and at worst would foul our propellers.
I think that what amazed me most about that place of huge skies and large lakes that opened into even more vast waterways, was how empty of other people it was on this lovely late-summer long-weekend, although we saw plenty of wildlife of all sorts. Once the moon set, a couple of hours before dawn, the sky shone with more bright objects than I have seen for ages, the Milky Way so low and thick I thought it was about to start raining stars at any moment.
So the moral of our tales is predictable enough and a familiar theme:
Ya simply can't put blind faith in machines - even those whose job it is to see...
I was navigating over a seamount with all applicable navaids running. When I was over the seamount, my depth sounder read 210 feet. When I was over 1000+ feet of water, it read 10 feet. I knew the echo was false because i knew my position by DR, radar, GPS, soundings from the seamount, and visual bearings on a nearby island.
Recently we were navigating around a series of lakes:
http://maps.google.com.au/maps?f=q&source=s_q&hl=en&geocode=&q=myall+lakes+nsw&sll=-25.335448,135.745076&sspn=42.067662,59.677734&ie=UTF8&hq=Myall+Lakes+National+Park&hnear=Myall+Lakes+National+Park,+New+South+Wales&ll=-32.449521,152.332993&spn=0.312317,0.466232&t=h&z=11
(if that long link is a problem, go to
http://maps.google.com.au/maps?hl=en&tab=wl
and enter: "myall lakes nsw" - then increase the magnification)
They're mostly shallow, but so was the draft of our houseboat. Nevertheless we had to navigate with care.
The water, particularly in the further lakes, is almost not salty at all, despite it being a system of sluggish flow and the sea not far, nearly fresh although this water looks like tea and tastes like tea because tea is what it is - vegetation-seeped.
We had a depth sounder which may have functioned just as it is supposed to, but there are extensive areas where 'seaweeds' (almost a monoculture of dense, mildly-prickly underwater bushes) grow almost to the surface and there, and even where they are a little underwater, the depth sounder signal seemed to bounce off a point somewhere deeper, where the growth was presumably thick enough to return it, although not off the bottom as indicated by the chart. It proved preferable to avoid these thick patches as much as possible, as at best they would greatly slow us down, and at worst would foul our propellers.
I think that what amazed me most about that place of huge skies and large lakes that opened into even more vast waterways, was how empty of other people it was on this lovely late-summer long-weekend, although we saw plenty of wildlife of all sorts. Once the moon set, a couple of hours before dawn, the sky shone with more bright objects than I have seen for ages, the Milky Way so low and thick I thought it was about to start raining stars at any moment.
So the moral of our tales is predictable enough and a familiar theme:
Ya simply can't put blind faith in machines - even those whose job it is to see...
