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Thread: Position updates faster than 1s or GPS with intertial sensor?

  1. #11
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    Quote Originally Posted by fluffy2097
    The garmin GPS 16a will probably work for anything you want it to. It's output is configurable, so you can make it send whatever sentences you want it to, as often as you want it to. I've hacked my GPS 35 to work with Travroute copilot and the 16A has the same capabilities.

    Mind telling us how you got the garmin to work with cp? I have a gps16

  2. #12
    Low Bitrate spectrumzz's Avatar
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    Quote Originally Posted by gork
    None yet.

    In combination with ODB-II engine logging and a fast-updating GPS (possibly with DGPS or WAAS), I'd like to write an track trainer/logger application that logs car position, throttle position, speed, acceleration, etc. through turns. You could drive a track or an autocross event and easily spot what you did wrong on a turn. This should have some pretty neat training / driver education applications. 1Hz updates, though, are really a bit slow for this, but 5Hz looks a lot better..

    Of course, it would also be nice to if it worked with some of the standard GPS apps that people here use like Destinator MapPoint, etc.. I really don't see why an application would care since they generally parse the NMEA streams and update every time they get a new position report.. The 16A output is still NMEA messages even though they are coming every 200ms instead of 1s..
    Most GPS systems are only good to 2-5 metres (such as the cheaper Garmin, the Earthmate and Deluo systems), which means that even at an update of once per second, they aren't accurate enough to plot tracks through turns. I am using custom software with my Deluo that updates every time a position comes across the wire, and while fast, the position isn't always quite right. What you are looking for is a very expensive high speed GPS unit.

  3. #13
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    what you're looking for is a military GPS unit

    if you really need accuracy and speed, you might want to read up on DGPS. but that'll involve synchronization with your base unit. duno if you wanna get that fancy

  4. #14
    Maximum Bitrate wi77iam's Avatar
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    Quote Originally Posted by spectrumzz
    Most GPS systems are only good to 2-5 metres (such as the cheaper Garmin, the Earthmate and Deluo systems), which means that even at an update of once per second, they aren't accurate enough to plot tracks through turns.
    The Earthmate is WAAS-enabled. The Deluo is not. WAAS capability improves position accuracy to < 3 meters. WAAS was designed to provide precision aircraft flight guidance, so I would think it is accurate enough to plot a car going around a bend.

  5. #15
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    Maybe if you bump up the baud rate of your GPS it would help. 4800 baud is standard, so maybe 9600 baud would help.

  6. #16
    phc
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    Quote Originally Posted by wi77iam
    The Earthmate is WAAS-enabled. The Deluo is not. WAAS capability improves position accuracy to < 3 meters. WAAS was designed to provide precision aircraft flight guidance, so I would think it is accurate enough to plot a car going around a bend.
    The problem with WAAS, is the 2 WAAS satellites are down on the equator, so unless you have a really good view to the south, you can't pick them up. Works great for Airplanes in the air and boats out at sea, but on land, its pretty hard to pick up.

  7. #17
    Maximum Bitrate wi77iam's Avatar
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    Quote Originally Posted by phc
    The problem with WAAS, is the 2 WAAS satellites are down on the equator, so unless you have a really good view to the south, you can't pick them up. Works great for Airplanes in the air and boats out at sea, but on land, its pretty hard to pick up.
    The satellites are geostationary so they have to be over the equator, but they are also at an altitude of 38500 km and are positioned to cover the entire North America. You only need to pick up one of them. More important is the location of the ground stations that supply the correction signals.

    My handheld Magellan Sportrak picks up the WAAS satellite about 75% of the time. I haven't been using my Earthmate long enough to tell how good it is yet.

  8. #18
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    Quote Originally Posted by krystar
    what you're looking for is a military GPS unit

    if you really need accuracy and speed, you might want to read up on DGPS. but that'll involve synchronization with your base unit. duno if you wanna get that fancy

    The millitary GPS that we use is about 10 -15 pounds, the size of a brick, and only accurate to 1 meter. If you dont have the proper crypto for the unit, it is only accurate to 10M. There is no base unit. It relys on satellites just like everything else. There are better commercial ones than the military use. You may pay 1500 dollars for them, but they would work a lot better. An avionics GPS would probably be the best your going to get because I know you arent going to get the proper crypto key to get 1 M accuracy. There are systems that claim they can get more accurate in the military, but they use systems that they claim they are more accurate than to be setup. I dont think the claims are true. Take it from me, I have 5 years using the military crap. It was made by the cheapest bidder, and it shows.

  9. #19
    Maximum Bitrate gork's Avatar
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    Quote Originally Posted by ScYThE
    The millitary GPS that we use is about 10 -15 pounds, the size of a brick, and only accurate to 1 meter. If you dont have the proper crypto for the unit, it is only accurate to 10M. There is no base unit. It relys on satellites just like everything else. There are better commercial ones than the military use. You may pay 1500 dollars for them, but they would work a lot better. An avionics GPS would probably be the best your going to get because I know you arent going to get the proper crypto key to get 1 M accuracy. There are systems that claim they can get more accurate in the military, but they use systems that they claim they are more accurate than to be setup. I dont think the claims are true. Take it from me, I have 5 years using the military crap. It was made by the cheapest bidder, and it shows.
    I have now done a lot of reading and refreshed myself on GPS.

    The military subcode channels from the GPS transponders is pretty much the same (really good) ionospheric delay information that you can get from WAAS now or various other DGPS methods including post-processing uncorrected data. The fact that it is transmitted along the exact same path from the same satellite as the GPS signal itself makes it quite a bit more accurate than WAAS for real time measurement (sub-meter vs sub 3m), but any other advantage to non-civilian GPS is all but negated since selective availability was generally disabled (the military subcode carries SA differentials when it is on)

    For the most accurate GPS data you can get you have to look to a unit designed for doing survey work. These typically require either post processing of the data or several known reference points closeby from which to continuously check differentials. They also tend to do a lot of averaging of multiple readings from the same position. However, they are the only way to achieve errors on the order of only a few cm from GPS. Pretty amazing stuff!
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  10. #20
    Variable Bitrate telekineticfool's Avatar
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    Quote Originally Posted by gork
    Well.. Now I just need to find a cheap Garmin 16A Anyone know of a good source new or used?

    UncoCow:
    Inertia-Only systems are fine if you get frequent reference points. In-car 1/4 mile timers and whatnot are good doing this type of thing, but I really was looking for something a little bit more accurate... perhaps using GPS/WAAS for reference points and interpolating with accelerometer sensors.
    Why reinvent the wheel: http://www.extremegeez.com/ is specifically designed for autocrossers who want to do what you're doing.

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