Do you sometimes need to find your way to an exact point on a planet, given the destination latitude and longitude coordinates ?
It has been suggested that you can do this by navigating north/south and then east/west along the meridians and parallels.
Although this method works, I think we, as pilots, can do much better than that and steer a course directly to our destination.
The first problem in navigating a planet is to find out which direction we are facing.
Unfortunately orbital cruise mode does not show your course bearing, so we have to drop out of OC mode and into flight mode to have a bearing display.
This can be done quickly by dropping out of OC at a very shallow angle and then pulling the nose up, this will terminate glide mode very quickly.
Bear in mind that this also has to be done if you are using the meridian/parallel method.
Having got the compass bearing display, the question is, which direction do we go in ?
One answer is to follow a "rhumb line", which is line of constant bearing that takes you directly to the destination.
Other lines are possible, including a great circle, but the rhumb line is the simplest for our purposes because once set, the bearing doesn't change.
There are several ways to calculate the rhumb line bearing which I will come to.
Having got a bearing, and brought the ship to bear, we have usually to go back into OC along that bearing. As we do not have a compass in OC, this can be done by choosing a suitable star near the horizon on the bearing line and keeping that star directly ahead during OC. As you approach the destination, the latitude and longitude coordinates should converge to the required values. They do so quite quickly in OC, so a correction may be needed on final approach. This can be done in normal flight mode.
So how to calculate the rhumb line bearing ? There are quite a few web sites which offer this calculation, look up "rhumb line calculator" on the web and choose your favorite.
Secondly, you can paste these formula into your favorite spreadsheet
dPhi = ln(tan(radians(lat2) / 2 + pi() / 4) / tan(radians(lat1) / 2 + pi() / 4))
bearing = mod(degrees(atan2(dPhi;radians(long2-long1))))+360;360)
where lat1,long1 and lat2,long2 are the start and end points.
Alternatively, and in memory of the old BBC micro that I first played elite on, I have written a couple of BASIC programs in BBC basic that will do the calculation for you. The first program is fairly basic and may run in BEEBEM, but I use BBC Basic for Windows (BB4W), which is available for download from http://www.rtrussell.co.uk/ There is a free evaluation version of BB4W which will probably suffice for both these programs. I run mine on a laptop next to my PC so I dont have to come out of the game. The second program only requires a couple of mouse clicks to set the positions (left mouse for departure point, right mouse for destination).
View attachment rhumb.txt
View attachment rhumb2.txt
PS I have no connection with Richard Russell, but would highly recommend BB4W
PPS I look forward to someone being able incorporate this feature into the game display itself. A bearing display in OC at least would be great.
It has been suggested that you can do this by navigating north/south and then east/west along the meridians and parallels.
Although this method works, I think we, as pilots, can do much better than that and steer a course directly to our destination.
The first problem in navigating a planet is to find out which direction we are facing.
Unfortunately orbital cruise mode does not show your course bearing, so we have to drop out of OC mode and into flight mode to have a bearing display.
This can be done quickly by dropping out of OC at a very shallow angle and then pulling the nose up, this will terminate glide mode very quickly.
Bear in mind that this also has to be done if you are using the meridian/parallel method.
Having got the compass bearing display, the question is, which direction do we go in ?
One answer is to follow a "rhumb line", which is line of constant bearing that takes you directly to the destination.
Other lines are possible, including a great circle, but the rhumb line is the simplest for our purposes because once set, the bearing doesn't change.
There are several ways to calculate the rhumb line bearing which I will come to.
Having got a bearing, and brought the ship to bear, we have usually to go back into OC along that bearing. As we do not have a compass in OC, this can be done by choosing a suitable star near the horizon on the bearing line and keeping that star directly ahead during OC. As you approach the destination, the latitude and longitude coordinates should converge to the required values. They do so quite quickly in OC, so a correction may be needed on final approach. This can be done in normal flight mode.
So how to calculate the rhumb line bearing ? There are quite a few web sites which offer this calculation, look up "rhumb line calculator" on the web and choose your favorite.
Secondly, you can paste these formula into your favorite spreadsheet
dPhi = ln(tan(radians(lat2) / 2 + pi() / 4) / tan(radians(lat1) / 2 + pi() / 4))
bearing = mod(degrees(atan2(dPhi;radians(long2-long1))))+360;360)
where lat1,long1 and lat2,long2 are the start and end points.
Alternatively, and in memory of the old BBC micro that I first played elite on, I have written a couple of BASIC programs in BBC basic that will do the calculation for you. The first program is fairly basic and may run in BEEBEM, but I use BBC Basic for Windows (BB4W), which is available for download from http://www.rtrussell.co.uk/ There is a free evaluation version of BB4W which will probably suffice for both these programs. I run mine on a laptop next to my PC so I dont have to come out of the game. The second program only requires a couple of mouse clicks to set the positions (left mouse for departure point, right mouse for destination).
View attachment rhumb.txt
View attachment rhumb2.txt
PS I have no connection with Richard Russell, but would highly recommend BB4W
PPS I look forward to someone being able incorporate this feature into the game display itself. A bearing display in OC at least would be great.
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