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Do you need a Compass if you have GPS? — Parallax Forums

Do you need a Compass if you have GPS?

rwgast_logicdesignrwgast_logicdesign Posts: 1,464
edited 2012-12-04 20:43 in Accessories
Basically the title says it all, if I buy a GPS can I use it as a compass also...

Comments

  • John AbshierJohn Abshier Posts: 1,116
    edited 2012-11-18 12:30
    A GPS can give you the direction you are traveling. If you are stationary, it cannot give you a direction. It cannot give you the direction from your location to something. That noted, many GPS do contain a compass.

    John Abshier
  • mindrobotsmindrobots Posts: 6,506
    edited 2012-11-18 13:50
    “You are standing in an open field west of a white house, with a boarded front door. There is a small mailbox here.”

    Ok, so you know where you are but not what direction you are facing.

    The Parallax VPN1513 has a Command to get your heading but if there's no motion, you have no heading. If you are standing still and spin, you have to way to reorient yourself to your previous direction, so you are not be able to resume course.

    With just a compass, you know which direction you are facing but no idea if where you are.

    You really need both for navigation.

    These are my assumptions, I haven't worked with these modules but I have used maps and compasses to navigate.
  • W9GFOW9GFO Posts: 4,010
    edited 2012-11-18 14:36
    John Abshier wrote: »
    A GPS can give you the direction you are traveling. If you are stationary, it cannot give you a direction. It cannot give you the direction from your location to something. That noted, many GPS do contain a compass.

    I think all handheld GPS units have a compass feature. Many only work if you are moving but quite a few actually have magnetic compasses in them too.

    The kind that have a 'software' compass will only tell you the direction you are traveling (course made good), not the direction you are heading - although they can be the same. A magnetic compass will tell you the direction you are pointing (heading) but not necessarily the direction you are traveling. This is most noticeable in air and sea navigation.

    Any GPS can tell you the direction to something (waypoint) if you specify where that something is. I think most of them even tell you the direction (bearing) calculated upon the great circle route.
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-11-18 14:51
    i want a compass for many things like face north travel two feet... and some sensor apps. in reality i dont need gps, i was just wondering if i could just buy a gps and use as a compass so id have a gps if i decided i needed one later
  • W9GFOW9GFO Posts: 4,010
    edited 2012-11-18 14:55
    For that you need a magnetic compass. Moving only a couple feet is not enough for a GPS based compass to deduce an accurate heading.
  • ercoerco Posts: 20,256
    edited 2012-11-29 09:07
    W9GFO wrote: »
    The kind that have a 'software' compass will only tell you the direction you are traveling (course made good), not the direction you are heading - although they can be the same.

    @Rich: Spoken like a man using mecanum wheels! :)
  • PublisonPublison Posts: 12,366
    edited 2012-11-29 09:29
    W9GFO wrote: »
    For that you need a magnetic compass. Moving only a couple feet is not enough for a GPS based compass to deduce an accurate heading.

    I like to use my old Boy Scout compass from the late 60's.
    Boy Scout Compass.jpg

    No, what box is that in......
    Boy Scout Compass.jpg
    1024 x 768 - 40K
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2012-11-29 10:42
    mindrobots wrote: »
    “You are standing in an open field west of a white house, with a boarded front door. There is a small mailbox here.”

    OT, but...Adventure? Zork? I haven't seen that text on my screen since 1988 or thereabouts.
  • mindrobotsmindrobots Posts: 6,506
    edited 2012-11-29 12:03
    Chris Savage wrote: »
    OT, but...Adventure? Zork? I haven't seen that text on my screen since 1988 or thereabouts.

    Opening lines from Zork. Yay, Infocom!
  • jimwreyjimwrey Posts: 3
    edited 2012-12-04 20:22
    Darn you both! I just spend a hour playing "Ghost Town" by Scott Adams because of your reference to Zork! Lost many hours back in the day to Zork and several of the games like Ghost Town.
  • Dr_AculaDr_Acula Posts: 5,484
    edited 2012-12-04 20:43
    @Publison
    I like to use my old Boy Scout compass from the late 60's.

    Nice one!

    Just the other day I needed to line up an east/west line for some solar panels. Could have fired up the GPS but it was quicker to get out the old boy scout compass. Reminds me of a funny experience running a camp for the scouts - we got a job lot of those compasses and handed them out with maps and half the kids hiked out into the bush and got lost. Turns out they had got the compasses that had been magnetized the wrong way!
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