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I didn't know about having to correct for magnetic vs grid north. Are the maps specialised for orienteering? Since I've never seen that info on a standard stre

by Jonnax 7y ago

I didn't know about having to correct for magnetic vs grid north. Are the maps specialised for orienteering? Since I've never seen that info on a standard street paper map. Is it something that a digital compass could automatically do? Especially since the article is indicating that magnetic north drifts.

nicolaslem 7y ago
Some maps provide this information but as it changes over time it's better to check it online beforehand. Useful tool: http://www.magnetic-declination.com http://www.magnetic-declination.com
isostatic 7y ago
In the UK the three compass points are on OS maps, sometimes with the changes predicted for multiple years. The older the map the less useful it is. You then have metal in the local rocks which can cause problems. Terrain recognition is far easier, there is far more error correction built in, but if you are hit by a patch of fog and visibility is down in to 30m (let alone 3m!) you need dead reckoning. Trouble is even a 1 degree error can turn into significant errors after a very short distance.
cmurf 7y ago
Aeronautical charts include this information. Terms are "true north" which is based on lat/long grid, and "magnetic north". An airplane has a magnetic compass as the primary reference, but it's a little wobbly, so on the ground prior to departure, a gyroscopic compass (called a heading indicator, directional gyro) is set to match the magnetic compass. If you do a some steep turns, or many shallower ones, you can get your heading indicator to drift. And if you travel some distance east or west it'll also drift relative to the magnetic compass, so you have to reset them to match periodically. The magenta dashed line going from top to bottom at a slight angle on the left of this image indicates degrees magnetic declination. https://www.faa.gov/air_traffic/flight_info/aeronav/media/VFRCarib.jpg https://www.faa.gov/air_traffic/flight_info/aeronav/media/VF...
shartshooter 7y ago
Great question! I had never thought of whether a smartphone points to grid or magenetic north. Quick google search shows that you can set at iPhone to either[1]. As for specialized maps for orienteering: Orienteering maps are different than normal street maps. They always have gridlines, very precise scales and clear markings of major and minor terrain features[2]. Then, on top of the data presented on a map you have maps of different scales. For example, one inch of a 1:24,000(pronounced - one over twenty four thousand) map represents 24,000 inches on the ground. A 1:250,000 map it very zoomed out relative to a 1:10,000 map. If you're hiking 500 miles of the PCT you may want a 1:100,000 or 1:250,000 scale map because you don't need to know every twist and turn because you're following a trail. But if I dropped you off in the middle of nowhere and said walk due west to a specific point 10 kilometers due westyou'd want a map that's 1:10,000-1:24,000 scale because you need to see specific terrain features. To answer your question more directly: There are what you would "orienteering-specific" maps because they represent some critical data well. For orienteering you use the one that works for you based on what information you need to get you from point A-B [1] - https://www.idownloadblog.com/2017/04/28/how-to-iphone-compass-apple-maps-navigation/ https://www.idownloadblog.com/2017/04/28/how-to-iphone-compa... [2] - https://pubs.usgs.gov/unnumbered/70039582/report.pdf https://pubs.usgs.gov/unnumbered/70039582/report.pdf

by Jonnax 7y ago

nicolaslem 7y ago

Some maps provide this information but as it changes over time it's better to check it online beforehand. Useful tool: http://www.magnetic-declination.com http://www.magnetic-declination.com

isostatic 7y ago

In the UK the three compass points are on OS maps, sometimes with the changes predicted for multiple years. The older the map the less useful it is. You then have metal in the local rocks which can cause problems. Terrain recognition is far easier, there is far more error correction built in, but if you are hit by a patch of fog and visibility is down in to 30m (let alone 3m!) you need dead reckoning. Trouble is even a 1 degree error can turn into significant errors after a very short distance.

cmurf 7y ago

Aeronautical charts include this information. Terms are "true north" which is based on lat/long grid, and "magnetic north". An airplane has a magnetic compass as the primary reference, but it's a little wobbly, so on the ground prior to departure, a gyroscopic compass (called a heading indicator, directional gyro) is set to match the magnetic compass. If you do a some steep turns, or many shallower ones, you can get your heading indicator to drift. And if you travel some distance east or west it'll also drift relative to the magnetic compass, so you have to reset them to match periodically. The magenta dashed line going from top to bottom at a slight angle on the left of this image indicates degrees magnetic declination. https://www.faa.gov/air_traffic/flight_info/aeronav/media/VFRCarib.jpg https://www.faa.gov/air_traffic/flight_info/aeronav/media/VF...

shartshooter 7y ago

Great question! I had never thought of whether a smartphone points to grid or magenetic north. Quick google search shows that you can set at iPhone to either[1]. As for specialized maps for orienteering: Orienteering maps are different than normal street maps. They always have gridlines, very precise scales and clear markings of major and minor terrain features[2]. Then, on top of the data presented on a map you have maps of different scales. For example, one inch of a 1:24,000(pronounced - one over twenty four thousand) map represents 24,000 inches on the ground. A 1:250,000 map it very zoomed out relative to a 1:10,000 map. If you're hiking 500 miles of the PCT you may want a 1:100,000 or 1:250,000 scale map because you don't need to know every twist and turn because you're following a trail. But if I dropped you off in the middle of nowhere and said walk due west to a specific point 10 kilometers due westyou'd want a map that's 1:10,000-1:24,000 scale because you need to see specific terrain features. To answer your question more directly: There are what you would "orienteering-specific" maps because they represent some critical data well. For orienteering you use the one that works for you based on what information you need to get you from point A-B [1] - https://www.idownloadblog.com/2017/04/28/how-to-iphone-compass-apple-maps-navigation/ https://www.idownloadblog.com/2017/04/28/how-to-iphone-compa... [2] - https://pubs.usgs.gov/unnumbered/70039582/report.pdf https://pubs.usgs.gov/unnumbered/70039582/report.pdf