Article 48004 of sci.geo.satellite-nav: Path: matra.meer.net!news1.best.com!newsfeed.nacamar.de!news.he.net!nr1.scn.co.jp!news01.so-net.or.jp!news3.sphere.ad.jp!news1.sphere.ad.jp!postmaster From: Chris Bryden Newsgroups: sci.geo.satellite-nav,rec.aviation.misc Subject: Re: 12XL fixes *better* at high speed Date: Thu, 09 Oct 1997 02:09:06 +0000 Organization: TMI Lines: 76 Message-ID: <343C3CC2.2F2A@sunnynet.or.jp> References: <343A30EA.445958AE@star.nl.compuware.com> <343ABDBD.665F@hrz1.hrz.tu-darmstadt.de> Reply-To: cbryden@sunnynet.or.jp NNTP-Posting-Host: max1-114.sunnynet.or.jp Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (Win95; U) Xref: matra.meer.net sci.geo.satellite-nav:48004 rec.aviation.misc:66594 Christian Schmadalla wrote: > > klaas wrote: > > > > Using a 12XL in a French TGV train (traveling 220 to 300 km/h) > > I noticed that it got a fix earlier than in a regular train > > (max. 160 km/h) and virtually did not lose track (unless in tunnels). > > Despite the thicker window glass. > > Possibly the *very fast* passing obstacles (trees, buildings, slopes > > along the railway line) do not block the sat signals as bad as the > > obstacles were passing slower. > > > > Any other experiences ? > > > > Klaas > > Another theory: In German trains, I never got my 12XL to work at all, > because the windows have a metal coating. Your regular train might have > such windows as well. Interesting. While traveling to Japan, I decided that it would be cool to try out my 12XL. I didn't know where the heck I was located at the time (about 5 hours into a great circle route from Hawaii), so I autolocated from a tiny window located in the door of a L1011 (I didn't have a window seat and I thought that it would be pretty rude to hold by GPS receiver upto the window across 2 other people). I didn't think this was going to work due the sky view I had out of the tiny porthole (less that 10" diameter), but to my surprise, I had an acceptable lock on 4 satellites within 15 miniutes (the amount of time required for an autolocate according to the manual). I took a couple of pictures to prove that I was able to do this; I couldn't belive it myself. I'll send them to anyone with an interest. Anyway, I spoke with the pilot after the flight and he indicated that the cockpit windows were heated and the current passed through the filliments in the windscreen interfered with the GPS signal, making the use of a hand held from the cockpit out of the question. Actually I don't think there are any filliments, but the windows are electrically heated (don't know the exact mechanism that is used to produce the heat, but I would be delight to hear from anyone that thinks they know). He also indicated that he had feried a 727 to pacific rim using a patch antenna that they ran from one of the passenger windows to a portable GPS arrangment in the cockpit. Interesting guy; wish I had more time to talk with him. On a related note, I used my GPS to monitor a flight within Japan. One of the flight attendants took a particular interest in my toys as asked me what they were (a newton MP 2000 and the Garmin). She even took the time to write the info down. 15 miniutes later she returned and asked me to turn my gear off, as it was causing problems with the gear in the cockpit. After the flight, I approached the flight crew to ask them exactly what gear was having problems. I really don't think they were expecting to have a licensed pilot quiz them and question their judgement (not my intent, I just wanted to know what to expect when I fly). I got a lot of heming, hawing and 10 molar sucking, but eventually they indicated that the TCAS (a collision avoidance system that uses transponder signals to localize aircraft collision threats) was the source of their concern. Pretty minor actually because ATC is responsible for providing seperation of air traffic; although, some less privilidged coutries in this part of the world might necessitate TCAS. I was glad that I turned my gear off anyway due to the crappy weather we had at the destination (IFR nearly requireing a go around from where I was sitting). Since we were flying from high to low pressure, it was cool to watch the actual altitude change as we rode the pressure gradient (the pilots set the altimiter to a fixed pressure above 18,000'). I just wished I had scanned in some maps of our route so I follow our progress. From what I understand TCAS is a pretty tempermental system anyway; doesn anyone have any datapoints on RF emissions from hand held GPS devices? I intend to use my GPS during the cruse portion of future flights anywhere near the North/South Korea boarder. Peace, love, understanding and, when all else fails, a big stick, -cfb