IddoB
Posts: 43
Joined: Wed Aug 23, 2017 4:39 pm

GPS that could work Indoors

Wed Aug 23, 2017 4:46 pm

Hi there,

I am looking for a GPS module that I could use indoors. It will be added to a project that I have been working on, autonomous car. I was looking to send to the car specific cords and having the car drive there. I dont want to buy a GPS module and then see that I cant use it with my project.

Thank you for taking your time to read this post.

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topguy
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Location: Trondheim, Norway

Re: GPS that could work Indoors

Wed Aug 23, 2017 9:15 pm

Most GPSs will not be accurate enough to navigate indoors anyway. And the sensitivity needed for a GPS to work indoors in the building you have in mind, is very dependent on the building itself and what it is made of.

Do you have a smartphone with GPS ? How well does it work in your building ?

klricks
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Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: GPS that could work Indoors

Wed Aug 23, 2017 9:39 pm

GPS modules themselves or any other GPS devices are not going to work well indoors unless you install an indoor GPS repeater system.

Google [Indoor GPS repeater]
Go here for my RPi writeup. Basic config, Serial Port add-on etc:
http://blackeagle12.net/Comp/RPi/Rpi.html Click contact icon then world icon --->

IddoB
Posts: 43
Joined: Wed Aug 23, 2017 4:39 pm

Re: GPS that could work Indoors

Wed Aug 23, 2017 9:53 pm

topguy wrote:
Wed Aug 23, 2017 9:15 pm
Most GPSs will not be accurate enough to navigate indoors anyway. And the sensitivity needed for a GPS to work indoors in the building you have in mind, is very dependent on the building itself and what it is made of.

Do you have a smartphone with GPS ? How well does it work in your building ?
Ive tried with my phone and it seems to work.

IddoB
Posts: 43
Joined: Wed Aug 23, 2017 4:39 pm

Re: GPS that could work Indoors

Wed Aug 23, 2017 9:58 pm

klricks wrote:
Wed Aug 23, 2017 9:39 pm
GPS modules themselves or any other GPS devices are not going to work well indoors unless you install an indoor GPS repeater system.

Google [Indoor GPS repeater]
Thank you for the suggestion. Does the car need to be directly connected to the repeater?

klricks
Posts: 4765
Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: GPS that could work Indoors

Wed Aug 23, 2017 11:24 pm

IddoB wrote:
Wed Aug 23, 2017 9:58 pm
klricks wrote:
Wed Aug 23, 2017 9:39 pm
GPS modules themselves or any other GPS devices are not going to work well indoors unless you install an indoor GPS repeater system.

Google [Indoor GPS repeater]
Thank you for the suggestion. Does the car need to be directly connected to the repeater?
No. See the diagram here: https://www.gps-repeaters.com/
(This link was at top of the list in a Google search)
Go here for my RPi writeup. Basic config, Serial Port add-on etc:
http://blackeagle12.net/Comp/RPi/Rpi.html Click contact icon then world icon --->

gkaiseril
Posts: 175
Joined: Mon Aug 08, 2016 9:27 pm
Location: Chicago, IL

Re: GPS that could work Indoors

Wed Aug 23, 2017 11:41 pm

GPS devices need to receive signals from at least 3 satellites to perform the needed calculations. The signals can be very weak so many devices use an large or amplified antenna. Most building have enough metal in their construction to block the weak signals. I would try adding an external antenna or look into both an amp and external antenna.

klricks
Posts: 4765
Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: GPS that could work Indoors

Thu Aug 24, 2017 5:58 am

IddoB wrote:
Wed Aug 23, 2017 9:53 pm
Ive tried with my phone and it seems to work.
On the phone be sure to test with the location service set to GPS only. (Disable network GPS).

Note that some phones don't have real GPS and get the location from network (Cell towers). They then provide GPS like data so that GPS apps work.

Some phones have both GPS and Network GPS and can be configured to use one or the other or both.
Go here for my RPi writeup. Basic config, Serial Port add-on etc:
http://blackeagle12.net/Comp/RPi/Rpi.html Click contact icon then world icon --->

IddoB
Posts: 43
Joined: Wed Aug 23, 2017 4:39 pm

Re: GPS that could work Indoors

Thu Aug 24, 2017 9:28 am

klricks wrote:
Wed Aug 23, 2017 11:24 pm
IddoB wrote:
Wed Aug 23, 2017 9:58 pm
klricks wrote:
Wed Aug 23, 2017 9:39 pm
GPS modules themselves or any other GPS devices are not going to work well indoors unless you install an indoor GPS repeater system.

Google [Indoor GPS repeater]
Thank you for the suggestion. Does the car need to be directly connected to the repeater?
No. See the diagram here: https://www.gps-repeaters.com/
(This link was at top of the list in a Google search)
Thank you. Ill read some more about it

IddoB
Posts: 43
Joined: Wed Aug 23, 2017 4:39 pm

Re: GPS that could work Indoors

Thu Aug 24, 2017 9:29 am

gkaiseril wrote:
Wed Aug 23, 2017 11:41 pm
GPS devices need to receive signals from at least 3 satellites to perform the needed calculations. The signals can be very weak so many devices use an large or amplified antenna. Most building have enough metal in their construction to block the weak signals. I would try adding an external antenna or look into both an amp and external antenna.
Ill have a look on it. Thank you for the suggestion

IddoB
Posts: 43
Joined: Wed Aug 23, 2017 4:39 pm

Re: GPS that could work Indoors

Thu Aug 24, 2017 9:29 am

klricks wrote:
Thu Aug 24, 2017 5:58 am
IddoB wrote:
Wed Aug 23, 2017 9:53 pm
Ive tried with my phone and it seems to work.
On the phone be sure to test with the location service set to GPS only. (Disable network GPS).

Note that some phones don't have real GPS and get the location from network (Cell towers). They then provide GPS like data so that GPS apps work.

Some phones have both GPS and Network GPS and can be configured to use one or the other or both.
Ive switched into GPS only and I still get a location

jahboater
Posts: 1803
Joined: Wed Feb 04, 2015 6:38 pm

Re: GPS that could work Indoors

Thu Aug 24, 2017 9:44 am

IddoB wrote:
Thu Aug 24, 2017 9:29 am
Ive switched into GPS only and I still get a location
Thats good, but I doubt its reliable. My Garmin GPS's can usually get a fix in a normal house, but only just - the signals are really weak.

The transmitters I believe are 1.5 watts and 11,000 miles away.

B.Goode
Posts: 4401
Joined: Mon Sep 01, 2014 4:03 pm
Location: UK

Re: GPS that could work Indoors

Thu Aug 24, 2017 9:47 am

Ive switched into GPS only and I still get a location
Is that location sufficiently accurate (and stable) for your requirement, and is it also responsive to changes to your actual position in the building?

[Count me among the doubters - probably including @jahboater - who think that unaided conventional GPS is unlikely to work well inside a building. ]

B.Goode
Posts: 4401
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Location: UK

Re: GPS that could work Indoors

Thu Aug 24, 2017 9:55 am

Since we now know from another post on the overall project that this is probably an assessed project for academic/training purposes, you might get additional marks if your write-up showed that you had investigated and understood the limitations of GPS.

Consumer SatNav and Google Maps make GPS look like 'always-there' magic: It isn't, it is a technology that has limits that you need to research.

hippy
Posts: 2180
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: GPS that could work Indoors

Thu Aug 24, 2017 10:00 am

I have used a u-Blox GPS receiver with an external aerial indoors while monitoring the raw data stream. One thing I noticed is that at various times of the day its reported location would jump significantly. I put that down to 'atmospherics' and satellites coming in and going out of field of view but don't know for sure. I didn't analyse the data for accuracy or determine how much the jump in location amounted to as that wasn't important for the work I was doing.

I would hope that anyone wanting to use GPS with an autonomous full-size vehicle will be using something far better than what one can buy off eBay for a few dollars but there could still be problems.

jahboater
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Joined: Wed Feb 04, 2015 6:38 pm

Re: GPS that could work Indoors

Thu Aug 24, 2017 10:07 am

The weak signals indoors will affect the accuracy.

GPS needs a minimum of 3 visible satellites to get a fix. Any more than that is called an "over-determined solution". It increases the accuracy and the reliability of the signal - if a satellite is blocked there are enough other satellites visible to retain the fix. My Garmin's seem to need 6 or 7 satellites before they even bother to report a position, but they are modern, sensitive (-159dbm?) 60+ channel receivers that can use Glonass as well.

You can watch the accuracy improve as more and more SV's are picked up.

The signal is so weak it is below the level of the thermal noise. The receivers detect patterns in the noise. Thats why it is so easily blocked.

IddoB
Posts: 43
Joined: Wed Aug 23, 2017 4:39 pm

Re: GPS that could work Indoors

Thu Aug 24, 2017 10:28 am

B.Goode wrote:
Thu Aug 24, 2017 9:55 am
Since we now know from another post on the overall project that this is probably an assessed project for academic/training purposes, you might get additional marks if your write-up showed that you had investigated and understood the limitations of GPS.

Consumer SatNav and Google Maps make GPS look like 'always-there' magic: It isn't, it is a technology that has limits that you need to research.
Yes I understood that and thats why Im looking to see if there are different soutions.

jahboater
Posts: 1803
Joined: Wed Feb 04, 2015 6:38 pm

Re: GPS that could work Indoors

Thu Aug 24, 2017 10:29 am

B.Goode wrote:
Thu Aug 24, 2017 9:55 am
Consumer SatNav and Google Maps make GPS look like 'always-there' magic:
Thats probably the way it should be for most users.

Handheld sets still have a decent "satellite" screen with lots of interesting information, but nowadays, reception (outdoors anyway) is so reliable, that I refer to the "satellite" screen purely for academic interest. I would be astonished if a fix could not be acquired, and recently, differential corrections (waas) seem to be quick and reliable too.

I remember the early days of single channel receivers (that were multiplexed around all the satellites) - then getting a fix took a very long time (many minutes) if it could be achieved at all. Tree cover, urban canyons, even heavy cloud, soon caused a lost position. A blocked satellite meant the entire acquisition process had to be restarted!

IddoB
Posts: 43
Joined: Wed Aug 23, 2017 4:39 pm

Re: GPS that could work Indoors

Thu Aug 24, 2017 10:40 am

jahboater wrote:
Thu Aug 24, 2017 10:29 am
B.Goode wrote:
Thu Aug 24, 2017 9:55 am
Consumer SatNav and Google Maps make GPS look like 'always-there' magic:
Thats probably the way it should be for most users.

Handheld sets still have a decent "satellite" screen with lots of interesting information, but nowadays, reception (outdoors anyway) is so reliable, that I refer to the "satellite" screen purely for academic interest. I would be astonished if a fix could not be acquired, and recently, differential corrections (waas) seem to be quick and reliable too.

I remember the early days of single channel receivers (that were multiplexed around all the satellites) - then getting a fix took a very long time (many minutes) if it could be achieved at all. Tree cover, urban canyons, even heavy cloud, soon caused a lost position. A blocked satellite meant the entire acquisition process had to be restarted!
Thank you for sharing this information

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Burngate
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Location: Berkshire UK
Contact: Website

Re: GPS that could work Indoors

Thu Aug 24, 2017 5:12 pm

klricks wrote:
Wed Aug 23, 2017 11:24 pm
IddoB wrote:
Wed Aug 23, 2017 9:58 pm
klricks wrote:
Wed Aug 23, 2017 9:39 pm
GPS modules themselves or any other GPS devices are not going to work well indoors unless you install an indoor GPS repeater system.

Google [Indoor GPS repeater]
Thank you for the suggestion. Does the car need to be directly connected to the repeater?
No. See the diagram here: https://www.gps-repeaters.com/
(This link was at top of the list in a Google search)
I'm not sure I understand how a repeater can help here - Or maybe I just don't understand GPS at all!

As far as I can see,the repeater gets four or more satellite signals from the aerial on the roof, and retransmits them all together from one place inside.
So, surely, the relative times of arrival of those signals depends on the position of the roof aerial, not the position of the car relative to either the satellites or the repeater.

So unless the roof moves, ...

IddoB
Posts: 43
Joined: Wed Aug 23, 2017 4:39 pm

Re: GPS that could work Indoors

Thu Aug 24, 2017 6:14 pm

Burngate wrote:
Thu Aug 24, 2017 5:12 pm
klricks wrote:
Wed Aug 23, 2017 11:24 pm
IddoB wrote:
Wed Aug 23, 2017 9:58 pm


Thank you for the suggestion. Does the car need to be directly connected to the repeater?
No. See the diagram here: https://www.gps-repeaters.com/
(This link was at top of the list in a Google search)
I'm not sure I understand how a repeater can help here - Or maybe I just don't understand GPS at all!

As far as I can see,the repeater gets four or more satellite signals from the aerial on the roof, and retransmits them all together from one place inside.
So, surely, the relative times of arrival of those signals depends on the position of the roof aerial, not the position of the car relative to either the satellites or the repeater.

So unless the roof moves, ...
Thats exactly why I was confused...

bensimmo
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Location: East Yorkshire

Re: GPS that could work Indoors

Thu Aug 24, 2017 9:02 pm

Use you phone, use a logger like Viewranger/Strava you'll seen see limitation, if you just go in woods.
(You would also see why it's pointless trying to get within seconds of top times).

Modern 'phone GPS' use maps from online of the sky to get a quick fix and a know location from transmitters/WiFi this is the A-GPS (Assisted GPS), SatNavs can do that if they are connected or if recently updated otherwise it can take quite a long time even in the open 10min/30 mins sometimes.

It also has in a limit to it's accuracy, which makes it poor for small area location and getting a direction is often done by Accelerometers/gyroscopes/Compass to help at slow speeds.
It's why some phones tend to be worse a Google Maps than others (they lack the Compass and/or Gyroscope), they're fine if you're going quickly but pack in under tunnels or slow traffic and take a while to catch up with sharp corners in towns.


A better method is to try setting up some triangulation system indoors, with your fixed known points.


That's my opinion and and what I've seen over the years of using GPS on MTB's, Cars, walking around cities and with the Pi (with a ublox) in rockets that go about 1km to 2 km and my bike.

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