NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Latitude AND Longitude by Noon Sun+GPS
From: Rodney Myrvaagnes
Date: 2004 Jan 25, 10:30 -0500
From: Rodney Myrvaagnes
Date: 2004 Jan 25, 10:30 -0500
On Sun, 25 Jan 2004 14:07:25 +1100, Kieran Kelly wrote:
--Original Message Text---
Frank makes two assumptions here:
1)the modern GPS is a reliable tool. I suggest it is not
2) That most GPS units purchased are by ocean navigators. Here again I beg to differ.
Re Point 1)
The GPS unit at sea I understanda very reliable and lifesaving instrument. The reason: The horizon on a boat is always visible. On land the horizon is often not visible for two reasons:
1) Overhanging tree and scrub cover and/or
2) The presence of gullies and gorges
I promise all list members from bitter experience that a GPS unit will not work in the dense scrubs of the tropical Australian deserts. It will also not work in the depth of the gorge country of Australia Kimberley plateau or in the deep ravines of the Victoria River. For example I went for four days
There is no need for the horizon to be visible. The receiver does need to lock 3 satellites for a 2D fix, 4 for 3D. The error circle for sats spaced less than optimally is a few meters, somewhat smaller than Australia. If the receiver program does not provide for 3-sat 2D fixes, you need 4 sats. This depends on the receiver.
Also, dry overhead foliage has not bothered any of the receivers I have tried in deep woods. Wet foliage is much worse. The sensitivity of receivers varies widely, as well.
Ravine walls will block the signal from sats below the ravine edge. However, with 12-channel receivers, four are often visible in the very deep canyons of Manhattan. That is most likely to happen at intersections of wide streets, of course. Ravines may not offer that convenience.
But I suggest that if you had carried a modern 12-channel receiver with a sound signal telling you when it gained and lost lock, you would have heard signals on occasion. If you were in a place where you couldn't climb out, your navigation would be constrained anyway. And CN would not be an option.
Rodney Myrvaagnes NYC J36 Gjo/a
"Curse thee, thou quadrant. No longer will I guide my earthly way by thee." Capt. Ahab
--Original Message Text---
Frank makes two assumptions here:
1)the modern GPS is a reliable tool. I suggest it is not
2) That most GPS units purchased are by ocean navigators. Here again I beg to differ.
Re Point 1)
The GPS unit at sea I understanda very reliable and lifesaving instrument. The reason: The horizon on a boat is always visible. On land the horizon is often not visible for two reasons:
1) Overhanging tree and scrub cover and/or
2) The presence of gullies and gorges
I promise all list members from bitter experience that a GPS unit will not work in the dense scrubs of the tropical Australian deserts. It will also not work in the depth of the gorge country of Australia Kimberley plateau or in the deep ravines of the Victoria River. For example I went for four days
There is no need for the horizon to be visible. The receiver does need to lock 3 satellites for a 2D fix, 4 for 3D. The error circle for sats spaced less than optimally is a few meters, somewhat smaller than Australia. If the receiver program does not provide for 3-sat 2D fixes, you need 4 sats. This depends on the receiver.
Also, dry overhead foliage has not bothered any of the receivers I have tried in deep woods. Wet foliage is much worse. The sensitivity of receivers varies widely, as well.
Ravine walls will block the signal from sats below the ravine edge. However, with 12-channel receivers, four are often visible in the very deep canyons of Manhattan. That is most likely to happen at intersections of wide streets, of course. Ravines may not offer that convenience.
But I suggest that if you had carried a modern 12-channel receiver with a sound signal telling you when it gained and lost lock, you would have heard signals on occasion. If you were in a place where you couldn't climb out, your navigation would be constrained anyway. And CN would not be an option.
Rodney Myrvaagnes NYC J36 Gjo/a
"Curse thee, thou quadrant. No longer will I guide my earthly way by thee." Capt. Ahab
