safisafo
Posts: 1
Joined: Mon Jan 14, 2019 12:51 am

Accuracy of GPS

Mon Jan 14, 2019 12:58 am

Hi. I'm using the SIM7600E module to take my latitude and longitude, but the result given is located like 30km away (very bad accuracy, like 3º), but it doesn't almost change. I'm running it indoors, is this normal?

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topguy
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Location: Trondheim, Norway

Re: Accuracy of GPS

Mon Jan 14, 2019 10:40 am

Can you link us a datasheet for the product you are using, because none of the modules with that name that turn up in Google actually have a GPS, its a 4G modem.

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bensimmo
Posts: 5653
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Accuracy of GPS

Mon Jan 14, 2019 3:15 pm

Something is wrong OR theit is the way you are reading the NMEA coordinates*.
It should get you within 10meters without a problem.. normally after a bit of time.

Apparently some models can have GPS.
https://www.waveshare.com/wiki/SIM7600E-H_4G_HAT


*There are different methods of representing coordinates.
But I should be degrees and minutes iirc
DDMM.MMMMM

Try http://www.hiddenvision.co.uk/ez/ to change to a different system and use that in your map.
Also if anything like the UK and you are sat in the meridian line then watch out for - E & W

pfletch101
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Joined: Sat Feb 24, 2018 4:09 am
Location: Buffalo, NY, USA

Re: Accuracy of GPS

Tue Jan 15, 2019 2:55 pm

bensimmo wrote:
Mon Jan 14, 2019 3:15 pm
Something is wrong OR theit is the way you are reading the NMEA coordinates*.
It should get you within 10meters without a problem.. normally after a bit of time.
I would not bet on this GPS accuracy (or even working at all) when run indoors, which the OP notes is his situation.

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bensimmo
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Location: East Yorkshire

Re: Accuracy of GPS

Tue Jan 15, 2019 4:24 pm

pfletch101 wrote:
Tue Jan 15, 2019 2:55 pm
bensimmo wrote:
Mon Jan 14, 2019 3:15 pm
Something is wrong OR theit is the way you are reading the NMEA coordinates*.
It should get you within 10meters without a problem.. normally after a bit of time.
I would not bet on this GPS accuracy (or even working at all) when run indoors, which the OP notes is his situation.
If it gives coordinates then it has a lock on a few satellite. So it has a a good radius to work with, maybe not 10 meters, but within 100m no problem. NOT 30km's ...
which sound like a unit mix up on the mapping program.

pfletch101
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Joined: Sat Feb 24, 2018 4:09 am
Location: Buffalo, NY, USA

Re: Accuracy of GPS

Tue Jan 15, 2019 4:44 pm

bensimmo wrote:
Tue Jan 15, 2019 4:24 pm
pfletch101 wrote:
Tue Jan 15, 2019 2:55 pm
bensimmo wrote:
Mon Jan 14, 2019 3:15 pm
Something is wrong OR theit is the way you are reading the NMEA coordinates*.
It should get you within 10meters without a problem.. normally after a bit of time.
I would not bet on this GPS accuracy (or even working at all) when run indoors, which the OP notes is his situation.
If it gives coordinates then it has a lock on a few satellite. So it has a a good radius to work with, maybe not 10 meters, but within 100m no problem. NOT 30km's ...
which sound like a unit mix up on the mapping program.
You may be right - if it is a GPS device. However, the OP also hasn't responded to topguy's implied question, noting (correctly) that the device the OP says he is using is a 4G modem with no GPS capabilities. Whatever he is using to get his location may be returning the location of the first router in his transmission path that admits to its location!

drgeoff
Posts: 13115
Joined: Wed Jan 25, 2012 6:39 pm

Re: Accuracy of GPS

Tue Jan 15, 2019 5:30 pm

The SIM7600E module does have GPS capability

See https://simcom.ee/modules/lte/sim7600e/ . Under General features "GNSS gpsOne Gen 8B;standalone;assisted,XTRA"
See https://simcom.ee/documents/SIM7600E/SI ... 20V1.1.pdf pages 1 and 5 for mention of GNSS antenna

But does whatever the OP is using have a GPS antenna connected to the SIM7600E?
Quis custodiet ipsos custodes?

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bensimmo
Posts: 5653
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: Accuracy of GPS

Tue Jan 15, 2019 5:37 pm

I posted a link to one, it has GNSS, aka GPS.

I doesn't mean it may not, but await to see.

EDIT , to above post, the Waveshare one is that chipset I linked to.
Also as it GNSS it has GLONASS, Beidou etc like my Ublox8. These connect indoors much better than my ublox6 which can fail to get a lock.

Anyway, back to await feedback.

teohhc
Posts: 3
Joined: Tue Jun 30, 2020 2:32 am

Re: Accuracy of GPS

Tue Jun 30, 2020 2:43 am

I am facing similar issue.

I've managed to get Raspberry Pi 4 working with Sim7600e similar to https://tutorial.cytron.io/2019/09/04/a ... 0e-module/

However, the GPS coordinates received seems to be 30km off.

There are 3 mode for the GPS session:
  1. standalone
  2. UE-Based
  3. UE-Assisted
However, managed to only get mode 1 & 2 working and still yielding the same result of 30km off.

For the 3rd mode, I did the following:
  1. AT+CGDCONT= 1,"IP","diginet","0.0.0.0",0,0
  2. AT+CGPSURL="supl.google.com:7276" # set agps url
  3. AT+CGPSSSL=0 # set security mode
  4. AT+CGPS=1,3 # start gps in assisted mode
But it will fail.

I am trying to improve the accuracy of the GPS. Anyway that I can achieve this?

teohhc
Posts: 3
Joined: Tue Jun 30, 2020 2:32 am

Re: Accuracy of GPS

Thu Jul 02, 2020 3:32 am

I collected further data to understand the situation better.

Switched the SIM7600e and GPS antennas to another spare set but getting same result. Hence, faulty device is ruled out.
Attachments
SampleDataAndDeltas.jpeg
Sample data and deltas
SampleDataAndDeltas.jpeg (192.07 KiB) Viewed 1235 times
GPSvsActual.jpeg
Adjusted GPS vs Actual route highlighted in green
GPSvsActual.jpeg (65.72 KiB) Viewed 1235 times
GPS-AdjustedGPS.jpeg
GPS from device vs Adjust GPS to starting position
GPS-AdjustedGPS.jpeg (170.58 KiB) Viewed 1235 times

teohhc
Posts: 3
Joined: Tue Jun 30, 2020 2:32 am

Re: Accuracy of GPS

Thu Jul 02, 2020 7:14 am

Thank you. Solved.

The device is not the problem. Problem is knowing which part of the number needs decimal point shifting and the remainder needing to be in minutes. Lat and Long using similar formula but Lat needs 100 more.
Attachments
testDrive2.PNG
Solved
testDrive2.PNG (158.74 KiB) Viewed 1199 times

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bensimmo
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Location: East Yorkshire

Re: Accuracy of GPS

Thu Jul 02, 2020 9:26 am

glad you got it sorted, saved me having a look :D

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