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How accurate is the gps — Parallax Forums

How accurate is the gps

Washer MedicWasher Medic Posts: 39
edited 2006-09-21 21:11 in General Discussion
We have a 100 ft by 400 ft landing strip out in the middle of the farm field would the gps be accurate enough to control an autonomous mower week after week without resetting code ect.

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There's nothing a good wack with a hammer won't fix

Darn I let the white smoke out again

Comments

  • metron9metron9 Posts: 1,100
    edited 2006-09-20 20:55
    The datasheet answers the first question.
    looks like 16.4 feet so mowing the lawn would be probbly not a good idea.

    I would think you could set up 4 becons though and find the becons via the GPS then mow from there.


    Not sure about the resetting code question.



    I think I may buy one of these to play with.

    Other Specifications
    • The navigation update rate of the GPS Receiver Module is once per second.
    • High sensitivity (-152 dBm for tracking and -139 dBm for acquisition).
    • The Module contains a built-in rechargeable battery for memory and real-time clock back-up.
    • On average, the Module has a +/-5 meter position accuracy and a +/-0.1 meter per second velocity accuracy.

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    Think outside the BOX!
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-09-20 21:08
    Remember, accuracy depends on many factors.· The number of satellites aquired, weather conditions, etc.· I prefer to use GPS navigation for way-points and in a situation like yours a beacon at each way-point would be a good thing.· It could be done though...See the following customer application.

    http://home.classicnet.net/dgps/

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    Chris Savage
    Parallax Tech Support
  • Kevin WoodKevin Wood Posts: 1,266
    edited 2006-09-20 21:14
    Based on the Parallax GPS document, their module is built around the Polstar PMB-248 module. Looking at the Polstar website, the PMB-248 uses a Sony CXD2951GA-4 GPS engine. The Sony datasheet gives a 2DRMS accuracy of approx. 2 meters.

    This figure would probably require WAAS support, and would also vary by field conditions.

    If anybody wants to see the Sony datasheet, you can find it on this Sony page:

    www.sony.co.jp/~semicon/english/list.html
  • Washer MedicWasher Medic Posts: 39
    edited 2006-09-21 04:16
    Thank you for your reply’s looks like I’m in over my head again confused.gif
    I need more info on the beacon idea but google is not helping me at the moment can
    someone steer me in the right direction
    Brian

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    There's nothing a good wack with a hammer won't fix

    Darn I let the white smoke out again

    Post Edited (Washer Medic) : 9/21/2006 6:51:14 AM GMT
  • hank van burenhank van buren Posts: 57
    edited 2006-09-21 12:43
    We have made a 2 stage "string" mower with a 38" swat ·to tow behind the gps controlled vehicle, using WAAS we where getting accuracies <2 feet at speeds of 2 mph
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2006-09-21 21:11
    Really good navigating robots I have read about use GPS and·a separate dedicated Compass Module.· Some use a beacon as a waypoint.· The beacon could be IR, Sonic, RF, Optical, etc.· The robot will use it to confirm it is in the area it should be in before continuing on to the next waypoint.· Way points are a good way to guide the robot around large obstacles that would take an unusually long time to map a way around itself.

    Pictures this...A robot is directed to coordinates for which a building stands in the way.· Obviously the robot doesn't know which way is quickest (left or right).· But if you specified via waypoint then the robot knows which way to go and just has to handle smaller distractions/obstacles.

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    Chris Savage
    Parallax Tech Support
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