NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: your mail
From: Dave Weilacher
Date: 2006 May 14, 13:10 -0400
From: Dave Weilacher
Date: 2006 May 14, 13:10 -0400
How about: Take a carpenters level and set it level at your height of eye. Take a straight edge laid alongside the carpenters level and pointed at the distant shore. Measure that angle. Use the compass rose from a universal plotting sheet. Wouldn't that be dip? -----Original Message----- >From: Alexandre E Eremenko>Sent: May 14, 2006 9:31 AM >To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM >Subject: Re: your mail > >Dear Roger, >Welcome to the list. > >> The first question I have is: I live on a hill overlooking the ocean >> but dont know my elevation to set the dip. > >There are several ways to do it. >1. Ask a friend who has a GPS to measure your altitude. My experience >shows that sometimes GPS gives errors up to 50 meters in altitude, >but usually it is OK. >(In the US, you do not even need a friend with GPS for this. >Just go to the department store, buy one, measure your altitude and then >return the GPS:-) >2. Take several Sun sights. >Take them with real horizon first, then with artificial >horizon. This method is not very precise though; you have to >take many sights and average them. You also have to determine >your index correction very precisely and to choose the time when the >real horizon is very sharp. >3. You say that you have a precise map of your neighborhood. >I suppose that this map does not show elevation of your house, >otherwise the problem would be trivial. >Now it depends on what you really see from your location. >Perhaps you can see some well defined shore line, or a building roof, >or any other horizontal line perpendiculat to the >line of your sight whose location and >distance >you can >determine from the map. Then measure the Sun's altitude against this >line. >4. Everything depends on the circumstances, on what you can really >see. For example, if you can see your house from the shore, >and the hill is really steep, you can try to measure the altitude >of your house roof from the shore using artificial horizon. >5. If you can see the horizon from your location in TWO OPPOSITE >directions, you can try a back sight (with some object in the sky >whose altitude is more than 60d. On your latitude, Sun can be used. >(I really envy your location if it permits you to do this:-) >6. The problem becomes much easier (and the solution more precise) >if you can use any surveying instrument (surveyors level, theodolite) >with a precise bubble level. > >Alex. >P.S. If needed, I can supply a formula for each case listed above, >or any other measurement you choose to try. Dave Weilacher .IBM AS400 RPG Senior Programmer Analyst/Project Leader .USCG Master lic. 100 ton .ASA Sailing Instructor Evaluator