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Improving GPS connectivity indoors — Parallax Forums

Improving GPS connectivity indoors

r.daneelr.daneel Posts: 96
edited 2013-10-18 16:34 in Accessories
Hi,

I have a PMB 688 GPS module that I'd like to use on my Stingray. I have it connected, I have written the code, and it works - sort of.

I have the optional external antenna, and when I connect that and hang it (the antenna) out a window the PMB 688 acquires sufficient satellite signals to get a position fix after a minute or two. The problem is that if I disconnect the external antenna and rely on the PMB 688's internal antenna, I never acquire sufficient satellites and so never get a position fix when the module is indoors (I haven't actually tried the internal antenna outdoors yet). While it's fine to hang the external antenna out a window to test the hardware and software, it's not really what I was looking for... The external antenna comes with a 3 metre cable, but I was hoping my Stingray would be a bit more mobile than that!

I have tried initialising the PMB 688 with the ECEF co-ordinates of its location, but that doesn't help.

Does anybody have any ideas on how I might improve the PMB 688's ability to see what I guess are weak signals indoors? Would a different GPS module be any better (the VPN1513 for example)?

Comments

  • Duane DegnDuane Degn Posts: 10,588
    edited 2013-10-09 20:01
    I've used two different GPS modules. One I purchased long ago from Parallax (they don't sell the same one anymore) and another was purchased from SparkFun (also discontinued).

    The difference between these two GPS units was night and day. The one from Parallax took over ten minutes outside in the open to get a lock while the one from SparkFun would get a lock anywhere in my house almost instantly.

    All I can say is to try to find out from others what GPS module currently sold does well indoors. I'm pretty sure the ones which work well indoors are going to cost more.

    I should clarify "works well indoors". Even if a GPS module can get a lock indoors, it's likely not going to be as accurate as when operating outdoors. GPS are generally intended for use outdoors. I doubt GPS will offer much assistance to indoor navigation.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2013-10-10 10:13
    I have the GPS with external antenna on my Stingray and what I've done is rolled up the extra cable inside the chassis with a tie-strap. I also wanted to say that while there may be some receivers out there sensitive enough to acquire indoors, they're intended for outdoor use and will always get a stronger signal outside.
  • r.daneelr.daneel Posts: 96
    edited 2013-10-10 14:08
    Chris Savage wrote: »
    I have the GPS with external antenna on my Stingray and what I've done is rolled up the extra cable inside the chassis with a tie-strap. I also wanted to say that while there may be some receivers out there sensitive enough to acquire indoors, they're intended for outdoor use and will always get a stronger signal outside.

    I did the same, but still no satellite lock. I understand they're primarily outdoor devices - I just wanted to play indoors. My Stingray's not going to spend a lot of time outdoors...

    Thanks Duane and Chris - I may just give up on the idea of GPS indoors.
  • Timothy D. SwieterTimothy D. Swieter Posts: 1,613
    edited 2013-10-16 05:00
    I've heard that GPS with helical antennas work better indoors, but this is dependent on GPS receiver sensitivity and what "indoors" is. A clear view of the sky is really what a GPS receiver needs. Signals received indoors are most likely reflections. Accuracy is lost.
  • ercoerco Posts: 20,256
    edited 2013-10-18 13:40
    Of course, indoor navigation through hallways and doorways in a typical house requires better accuracy than GPS can give you. Unless you're the rascal who bought the Upstate Castle right out from under me, with the attached gymnasium/armory which would be the PERFECT place for testing GPS robots... somebody got a deal (?) on this place.

    http://upstatecastle.com/

    http://www.nytimes.com/2013/04/23/booming/their-castle-could-be-yours-for-under-a-million.html?pagewanted=all&_r=0
  • pmrobertpmrobert Posts: 673
    edited 2013-10-18 16:34
    I've found that roofing/celing construction has a major effect. I get signals as good as outside under drywall or tongue and groove wooden ceiling,wooden rafters, plywood roof deck, tarpaper and asphalt or fiberglass shingles. Any metal or heavy masonry (clay, barrel tile, concrete) and signal is only partially available by window and door openings.
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