FWIW: I'm using a LEA-6T with a $6 ebay magnetic puck sitting on a 1m x 1m wire-mesh groundplane. This is on a mast about 1 m above my chimney and it has a pretty clear view down to the horizon in most directions. I have experimented with different satellite mask angles in RTKLIB and 5 degrees gives me the solution with the lowest variability. Using the same antenna in the same place with only a 20 cm groundplane, I did better with a 15 degrees cutoff.
Using a 24-hour observation period and PPP-Static solution (just my single receiver; not using data from any other station) my ground track typically fits into a box 7 cm (E-W) x 3 cm (N-S) x 5 cm (U-D), and the day-to-day variation has been about 10 cm horizontally and 20 cm vertically over a few weeks now. I have not been taking into account "solid tides" but at this level I probably should. The scatter in the results does not look random between days; there seems to be a consistent rise in elevation during/after a rain so I'm wondering if I am seeing some local atmospheric effect, or actually a true elevation change due to groundwater (I don't think my 7 m chimney expands 20 cm after a rain). -John B > -------Original Message------- > From: Danny Miller <[email protected]> > To: Open Source GPS-related discussion and support <[email protected]> > Subject: Re: [FOSS-GPS] Good antenna > Sent: 10 Mar '14 22:26 > > Really? I thought helix antennae were poor choices because they accept > signals at low angles. In fact the article makes a point of saying it > accepts low-angled signals. > > From satellites coming in at only 5 deg above the horizon, they're prone > to distortion from the atmosphere and ground obstacles. Now the software > can just refuse to use those satellites because it knows the angles from > the ephemeris data. > > But as I understand it, a lot of the multipath reflections- delayed > versions of the original signal bouncing off things- often comes in at a > low angle, so the antenna rejecting the low-angled reception will help. > These signals traveled a longer path and only distort the pseudorange. > Since this is a feature of the antenna, software can't just elect to > reject these signals- and it if could, it would. _______________________________________________ This message is sent to you from [email protected] mailing list. Visit http://lists.osgeo.org/mailman/listinfo/foss-gps to manage your subscription For more information, check http://wiki.osgeo.org/wiki/FOSS-GPS
