Featherweight GPS questions

Discussion in 'Rocketry Electronics and Software' started by micro, Nov 22, 2019.

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  1. Nov 22, 2019 #1

    micro

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    Just got my GPS units a couple days ago. I'd like to be fluent before I take them to the field.

    It's not clear which functions even work yet. The website needs to be more clear on how beta this product is.

    Is spoken telemetry implemented yet?

    Do you need to be unlocked and on a certain page for spoken telemetry to work or will it automatically start when launch is detected?

    How will spoken telemetry work with multiple stages? Will they talk over each other in a scrambled mess or do you set primary or does only one report?

    How do I read the satellite graph on the GPS page? Does the number in the colored square beneath the rectangle show the total number of satellites tracked and the color of the square represents the overall resolution? That's what I'm guessing but the instructions don't say that.

    On the Track page, how do I switch to my other tracker unit?

    Does the sim function work? It pushes me to the Track page but no values change.

    I see recordings created by the sims (I assume), how do I delete them?

    Does the battery V indicator have a 6V maximum? It says 6.112V when it should be 8V on my battery.

    Thanks,
     
  2. Nov 22, 2019 #2

    manixFan

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    For spoken telemetry:
    • change the screen auto-lock delay to 5 minutes via iPhone Settings
    • make sure mute switch is off
    • turn up volume
    • be on tracker page
    • don’t put phone to sleep (which you won’t want to anyway, otherwise how can you track your rocket?)
    that’s it, it will automatically call out once in flight.

    The satellite question is answered in the users guide:

    https://www.featherweightaltimeters.com/uploads/1/0/9/5/109510427/manual_2018june18.pdf

    I’m sure you’ll get guidance on the other questions.


    Tony
     
    Last edited: Nov 22, 2019
  3. Nov 22, 2019 #3

    micro

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    Thanks Tony, glad to hear voice telemetry will work for a single stage launch at least.

    I wonder what will happen and how useful it will be for multi stage flights. For example I'd like to keep my eyes on the sustainer but hear an alert when the booster has an apogee event so I know everything is going well.

    The manual doesn't describe much about the satellite graph. It says the bar graph represents 24 satellites. What does the number below the graph mean? In the manual graphic is that 3 satellites? If that's the case why are the bar graphs different sizes when both numbers are 3? And why are the bars different sizes? We have a chart of colors but we don't know what the size and layout of the bars mean nor what the numbers represent.
     
  4. Nov 22, 2019 #4

    manixFan

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    sat-display.jpeg The sat info is in the manual. The number below the graph is the satellite count. The colors represent the strength of the signal, and the size of the color bar represents what portion of the satellites are at that signal level. So in my screenshot above, the ground station has 20 sats, and the tracker has 19. The small blue bar at the top of the tracker graph means that a couple of the satellites have a signal strength of 40 or better, so have full accuracy. The top colors are the best accuracy, the lowest are the worst. So you want a lot of blue and green. I wear my receiver in a case on my waist, which is not the best for the GPS receiver.

    You can switch between trackers by using the picker at the bottom of the GPS screen, then switch to the track page. So you could track the booster during the beginning of the launch and then switch to the sustainer later in the launch. You can tell pretty quickly if you have an apogee event by the change in vertical velocity. But it would be far better to find another flyer with a base station so you can track both stages without having to switch between them.

    The sim function does work. You access it on the Devices page by selecting a connected tracker. (Must be on and connected via Bluetooth.) Then choose Run Sim and enter the values you want to use. It only works if you have an active connection to the tracker.

    Based on my experience and several others in my club who use the trackers, it is a great system and very robust for the price. Now that we can export flight logs and plot them (albeit with a little work), it's even better.

    Good luck,


    Tony
     
  5. Nov 23, 2019 #5

    micro

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    Why is one of your GS satellite count (20) in green and your tracker count (19) in gray?

    And why do the bar graphs in the manual take up 1/3 of the graph when there are only 3/24 satellites represented? If there are 3 satellites and 3 colors represented, shouldn't all three bars be equal size?

    Screenshot_20191122-181558_resize_4.jpg
     
    Last edited: Nov 23, 2019
  6. Nov 23, 2019 #6

    manixFan

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    I suspect the image in the manual is not a 'real' screen grab, but just an example. Don't worry about the image from the manual. As you can see from my screen grab above, it is scaled correctly. I've attached additional images below that show it's scaled correctly and how the color changes to represent signal quality.

    The reason for the difference in satellite count is simple. The tracker is under main and has a clear view of the sky, so it has a higher count than the ground station. As I mentioned before, my GS is in a case that I wear clipped to my belt. It hangs down vertically and is partially blocked by my body, so it does not have a good, clear view of the sky. That is also represented by the colors of the charts.

    Not to knock on Kevin, but I do admit the graphics could use a little work. But they in no way affect the functionality of the system.


    Tony

    Screen-01.png Screen-02.png Screen-03.png
     
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  7. Nov 24, 2019 #7

    warnerr

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    Great tracker! Be sure to get the latest release of the software a couple of days before you go- update phone- and ALL devices you have- trackers and receivers- everything must be updated to same version. Once on field do not do updates.
     
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  8. Nov 24, 2019 #8

    vahpr

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    The manual is in process of a re-write which hopefully will flesh out and clarify the operation and functions. Warnerr, we actually did an on-field update at Balls this year so it's possible, but of course this is better done while you bench test it home. Agreed, it's a great tracker.
     
  9. Nov 26, 2019 #9

    micro

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    I played with the system some more and I still can't get the sim function to work. I can hear all the voices in settings so clearly my sound works but when I activate the sim it transfers me to the track page but nothing happens. Not sure if the angle field is degrees from vertical or horizontal, and nothing in the manual, but I've tried 0, 45, 90 and no stats change on the track page.

    I did figure out how to change between trackers, looks like the only way is to go back to the GPS page, change trackers, then scroll back to the track or comm page.

    I thought maybe I'd delete and re-add the trackers but it looks like there's no way to delete them. I can try to wipe the program and start fresh.
     
  10. Nov 26, 2019 #10

    Voyager1

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    I’ve tried to delete log files from the list but it doesn’t happen. What am I missing?

    upload_2019-11-26_12-38-56.png
     
  11. Nov 26, 2019 #11

    timbucktoo

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    As Kevin said, you can’t yet with current release.
     
  12. Nov 26, 2019 #12

    micro

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    After a few power cycles and some more putzing around with the interface the sim started to work. :shrug:
     
  13. Nov 26, 2019 #13

    ksaves2

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    No matter what system you use, make sure you have a good satellite lock. Kurt
     
  14. Nov 26, 2019 #14

    micro

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    That's the thing, I wish we had better data to make that determination. I often see what Tony shows in the first pic where what we assume to be the satellite count is in a gray box, but we don't know what gray box means.
    Screenshot_20191126-175449~2.png
    Is gray box bad? Should I launch? I don't know.
     
  15. Nov 26, 2019 #15

    watheyak

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    Deleted post.

    Better information has been presented.
     
    Last edited: Nov 27, 2019
  16. Nov 27, 2019 #16

    kjs

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    Sorry for delayed responses. I've had a server die at work and most awake time has been getting that resolved.

    So if your GS looses COMM with the tracker for more then 5 seconds, it starts counting up time in the title bar and the coordinate info on the GPS page goes gray (presumably the sat count as well). I can not current explain the gray sat count while other numbers look OK so I will check the code and get back to you on that.

    other comments about stuff on this thread:

    Yes I want to move the selection wheel to the track page as well.

    I once had it so you could swipe between rockets, but then someone accidentally swiped to keep their phone 'awake' and I realized it was too easy to swipe away from the rocket you want to track so I removed that.

    For SIM to work, you should be connected via bluetooth to both the GS and the TRK. The TRK link is to command the TRK to run the sim SIM, but all signals come back by way of TRK->Lora->GS->BLE->Phone (so like a normal flight). If it switched to the SIM page but you did not have your GS on and paired with the tracker, you would see no sim / hear no sound.

    As far as being ready to launch, you should be able to see numbers changing and you don't want to see a count of time in the title bar counting up from when you last heard from your rocket. I'm going to update the track page to go red in some way if you don't have COMM with the rocket.

    Continue to provide inputs - work has been a little busy but I welcome them and will be working on updates!
     
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  17. Nov 27, 2019 #17

    kjs

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    Ah... the question as to why the "three satellites" in the docs took up almost a third of the bar is because originally that 3 was for 3D fix (before I started reporting actual count of satellites).

    For the satellite box color, it should be:
    - gray for "lost contact with tracker for > 5 seconds"
    - yellow for "talking to tracker but it doesn't have 3D lock yet"
    - green for "talking to tracker and it has 3D lock"

    I still have to think of what would cause the sat to be gray but not the locations. usually I gray the locations when I haven't heard from the tracker in 5 seconds...
     
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  18. Nov 27, 2019 #18

    kjs

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    I realized that is an early screen shot when the 3 meant 3D fix as opposed to the number of satellites. sorry about the confusion...
     
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  19. Nov 27, 2019 #19

    manixFan

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    The GPS unit can track up to 24 satellites, the more the better the accuracy of the location (generally). You need at least 4 satellites to work out your location in 3 dimensions, more is better. So as long as you have at least 4 satellites it will track your rockets location. Since rocket launches are held outdoors in (hopefully) clear areas, you should never have an issue getting a good lock on multiple satellites. The exception might be if you have mounted your tracker in such as way that the receiver does not have a good view of the sky or the signal is blocked by a metal mount (like some all-thread) or a radio opaque material such as carbon fiber.

    After looking at my screen recordings, it seems the satellite tracker data is all gray when you flip to the GPS screen from the tracker screen. Generally all the data turns green all at once. But sometimes there is a lag and the count box takes a moment before it turns green. So maybe it's just a lag in updating the box color and nothing more.

    micro, one thing to consider is that many have flown the tracker with great success with the currently available information without issue. As long as the boxes are green when you start and you have mounted the tracker in a good location, it's pretty hard to screw up.


    Tony
     
    Last edited: Nov 27, 2019
  20. Nov 27, 2019 #20

    micro

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    Thanks for those explanations, that makes a lot more sense!
     
  21. Nov 27, 2019 #21

    Voyager1

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    Thanks Tim. Didn’t see that statement.
     

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