3 ms·
> GPS is not involved in this change really. How do you determine true north without a GPS system?
by chrisseaton 5y ago
> GPS is not involved in this change really.
How do you determine true north without a GPS system?
- lxgr 5y agoWouldn't it be possible to broadcast local magnetic declination over ATIS or other automated broadcast systems? As far as I know (and according to the article), modern navigation systems contain databases of the local magnetic declination anyway; instead of updating maps and navigational databases, we could just update these declination database instead every once in a while if I understand it correctly.
- chrisseaton 5y agoHow do you apply these things without knowing where you are? True/magnetic deviation is localised. You need to know where you are to know what the localised value is.
- lxgr 5y agoWouldn't a very rough location suffice, i.e. something that could be either manually set (for general aviation and shorter distances), derived from a VOR station identifier or similar, or just estimated via dead reckoning/an INS? In other words, if you don't even have a rough idea of where you are, what good will a magnetic heading do?
- chrisseaton 5y agoRough yeah - but I think it does change by integer degrees from actual map sheet to map sheet, so you could probably drift a couple of degrees without knowing it within an hour or so of flying.
- lisper 5y agoHow do you determine true north with a GPS system? GPS only gives you your position, not your orientation.
- chrisseaton 5y ago> How do you determine true north with a GPS system? def true_bearing(magnetic_bearing, location) magnetic_bearing + gma(location) end And that's the point - your true bearing is a function of your location.
- lisper 5y agoAh. Right. Duh. (I must be having an even worse day than I thought.)