PDA View Full Version : Rhumbline track rpetersson8th Jun 2012, 09:00Q: From N65 00 E010 00 to N65 E052 00 on a rhumb line, what is the distance? a 1065 nm b 2283 nm c 1700 nm d 2520 nm I got it to 2520 just by taking E52-E10.. but im not sure if this is right can anyone confirm? Q: An aircraft flies from N32 00 E020 00 for 1200nm on a rhumb line track of 090, what is the longitude of the new position? a E013 58 b E043 35 c E050 00 d E040 59 This one i calculated again just taking 1200/60 = 20 and adding it to E020 and getting E040..... But it doesnt seam to be correct if i look at the possible answers.. can anyone help me here? Thanks in advance... (Im abit unsure when the question says rhumbline track if i have to deal with convergency or not....) rpetersson8th Jun 2012, 09:45Found out...that....the departure formula is the shit :) alex2303808th Jun 2012, 09:47concerning the 2nd question you propose: If you keep a constant hdg of 090° means you're tracking a rhumb line and necessarily also a constant Latitude. You need to use the departure formula which is: Dep=ch long(in minutes ')*cos Lat. 1200nm=ch long(') * cos 32° 1200nm=ch long(')* 0.848 ch long(')=1200/0.848 =1415.1' =23.58° =23° 35' further east new position: N32° (unchanged), E43° 35' remember, the distance between two meridians spaced 1° is 60nm only at the equator, and 0nm at the poles. At 30°N is 60*cos30°=51.96nm , at 70°N is 20.5nm and so on. ciao SunderlandMatt8th Jun 2012, 10:05RP, These questions both ask you for the rhumb line track along a line of latitude. What they are after is the departure i.e. the distance between two points. Departure = ChLong x Cos Lat Q1. Departure = 42 (degrees between the two points) x Cos 65 (latitude) = 16.9 (degrees at correct scale) x 60 = 1014 nm I'd therefore go for answer a) as it's closest. Q2. Here they want you to rearrange the Departure formula to obtain ChLong to find the new longitude. Departure = ChLong x Cos Lat ChLong = Departure / Cos Lat ChLong = (1200 / 60) / Cos 32 (1200 is divided by 60 to get it into degrees) = 23:35 So E020 + 23:35 = E43:35 which is answer b). You use Convergency as soon as great circles are mentioned. Departure is used on rhumb lines. Hope that helps. SM. whiskey18th Jun 2012, 10:15Rhumb Line may be a straight line on a Mercator Chart. It is a line of constant bearing. So a line of Latitude is a Rhumb Line (and yes the equator is both a Rhumb Line and a Great Circle). A Rhumb Line is NOT a straight line on the Earth, a Lamberts Chart or a Polar Sterographic Chart. rpetersson8th Jun 2012, 10:20Thanks for all the great answers, love you guys <3 RichardH8th Jun 2012, 10:56A Rhumb Line is NOT a straight line on the Earth, a Lamberts Chart or a Polar Sterographic Chart. It is if it's along a Meridian of Longitude which is either 360 or 180 therefore constant direction. They are also great/semi-great circles.