Path: news.eternal-september.org!eternal-september.org!feeder3.eternal-september.org!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Jeff Liebermann Newsgroups: rec.bicycles.tech Subject: Re: Food Prices Date: Mon, 02 Jun 2025 10:24:18 -0700 Lines: 82 Message-ID: <9flr3khbme4hscgpbmk9dtk3ftghdbj3vu@4ax.com> References: <9MKYP.163084$0DKa.113787@fx14.iad> <7ndm3k1hlpcg6redqspneugtd9gdq0d2op@4ax.com> <101fpjn$1dogt$3@dont-email.me> <5kqm3k5u383itrg850lif251ocpf4tq1rs@4ax.com> <101g82j$1hvsg$4@dont-email.me> <09cn3k1amaj41pvilj3pt61458a60djrth@4ax.com> <101jqtq$349bv$1@dont-email.me> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: individual.net YNnn8j50bgexEOV2X9NcZQQXW5BitE5Ga4Kjv/solTspZEtdsx Cancel-Lock: sha1:3roarTLo/yBpoR6vQMxFQ8xMLzc= sha256:NOjPp51ieDW0ipd87eeB7XApCZ+ZBN2F7Oqta1Eo9Sg= User-Agent: ForteAgent/8.00.32.1272 On Mon, 2 Jun 2025 11:29:31 +0200, Rolf Mantel wrote: >Am 01.06.2025 um 04:26 schrieb Jeff Liebermann: >> On Sat, 31 May 2025 20:49:21 -0400, Frank Krygowski >> wrote: >> >>> On 5/31/2025 5:07 PM, Jeff Liebermann wrote: > >>> The >>> rest were not hard, mostly because of quirks: I've got a repair project >>> pending on my side porch steps; I had to align my reflecting ceiling >>> sundial with due north-south, and learned my house is precisely oriented >>> that way... etc. >> >> In the distant past, I use an analog watch: >> >> The tricky part is dealing with daylight savings time. >> >> These days, I find a printed paper road map. I locate two points. One >> is my own location. The other is an identifiable landmark in the >> distance. Mountain peaks work well. Lay the map on a flat table. >> Align on the map your location and the distant landmark. True north >> is printed on the map as an arrow. > >In my region, we have several north-south lines as features: > >Directly south of Heidelberg, the hill edges, the old Roman road, the >railway line and the motorway are all parallel North-south lines. > >The Rhine from Speyer to Mannheim flow due North though not exactly >straight. > > When I displayed the link on my desktop, I noticed that there was no compass symbol or compass rose. However, on my Android phone, just tapping the two concentric circles in the lower right, would toggle the compass display. Obviously, it makes little sense to display a compass on a desktop that doesn't rotate or move much. >At bit further to the North, the motorway A67 goes perfectly to the >North for 25km. Perfect north? Many years ago, before WAAS, RTK and other GPS accuracy enhancements were available, we were using "differential GPS". The system featured pseudolites (ground based GPS satellites) that would broadcast satellite corrections using the low frequency marine navigation system. In order for it to function correctly, the location and altitude of the pseudolite needed to be located extremely precisely. I forgot the survey accuracy that was required, but I think it was within a few cm. I had to go through some contortions to deal with changes in location caused by continental drift, tidal variations, earthquakes, etc. I also had the same problem using GPS to check the official survey markers along my road. I'm not up to date on the magic currently used to correct the corrections, but I can assure you that even the largest objects (i.e. motorways) will move substantially. To be fair, I doubt these movements will be noticed using a magnetic or flux gate compass. Certainly, nobody needs that kind of resolution and accuracy in a hand held device. However, I suspect that there will be substantial changes that will be noticed for long baseline measurements (motorway again) and long time spans (years), especially if the motorway crosses an earthquake fault line or lubricated feature (rivers). Fairly inexpensive RTK products: 1.4cm accuracy. >On a grander scale, the Rhine Rift Valley goes in a straight line >North-to-Northwest 200km (125 miles) from Basel to Bruchsal (with edges: >black Forest and Vosges in France) and then heads straight North for >another 50 miles from Bruchsal towards the end at Frankfurt / Mainz (the >Odenwald as eastern edge gives a good North-South approximation, the >western edge is less sharp). > >Rolf -- Jeff Liebermann jeffl@cruzio.com PO Box 272 http://www.LearnByDestroying.com Ben Lomond CA 95005-0272 Skype: JeffLiebermann AE6KS 831-336-2558