HDOP values good enough for positional accuracy?

Hi all, we are using a EG2x in our device that’s going to be used for package monitoring, sampling location every 15 minutes.

With each location fix received from the EG2x, our device’s MCU will need to make sure if that location fix symbolizes a violation from a list of geofences that we’ll be keeping onboard the device.

The question is: what is an acceptable maximum HDOP for these geofence violation determinations?

Wikipedia has this table for interpreting DOP:

If I’m reading that table correctly, HDOP of 10 or better would be acceptable for these geofence violation determinations, as HDOP 5-10 in that table means “Positional measurements could be used for calculation”

…whereas HDOP 10-20 in that table means “Positional measurements should be discarded or used only to indicate a very rough estimate of the current location”.

Is this table accurate as far as the EG2x’s GNSS module’s HDOP calculations?

If not, what would be an appropriate minimum acceptable HDOP for the EG2x to make positional calculations – such as geofence violation determinations?

Thank you for your help!

Hello @Philip_Schlesinger Glad that you’re back to the Quectel Forum. :slight_smile:
@mandy.wang and @Raphael-Q can better assist you with your issue.
I have an “ongoing case” similar to your problem. Have you tried to email Quectel support?
If not, I highly recommend you to do so.
With more details and logs when you send your message, they can fastly and better assist you.
@Akso.xie and @eddy are the administrators of the forum, maybe they can better guide you, or assist you.
The app “GNSS view” (for Android cellphones) provide some values accordingly to the GNSS of your mobile, including HDOP. Is this useful for you?

Have a great weekend :slight_smile:

Hello,Akso. ​Xie and Eddy aren’t in charge of the forums category. Each section has corresponding technical moderator responsible. Due to the large number of posts, they need time to reply. Please be patient, and we will also push them to support you as soon as possible.
Thank you for your understanding. :grinning:

BTW, for GNSS module or related issue, @Raphael-Q will support you, many thanks~ @Philip_Schlesinger

Thank you @Niki.Liu-Q and @ShortyPTG for your responses.

@Raphael-Q looking forward to hearing your recommendation based upon my question above. Thanks!

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Hi Philip Schlesinger,

Generally, for GNSS module, we don’t take HDOP for main reference.
If HDOP<2, that means the location should be accurate.
If HDOP<5, the location may have drifts.
If HDOP>10, the location should be inaccuracy.

The performance of GNSS location is mainly influenced by the environment. If the sky is blocked, or surrounded by tall buildings, the location would be inaccurate and HDOP would rise.

Best regards.

Hi @Raphael-Q

Generally, for GNSS module, we don’t take HDOP for main reference.

If you don’t use HDOP for the GNSS module to state the level of quality of a location fix, what parameter should we be looking at to determine if a location fix is good enough for detecting a geofence violation?

Separate question:
Do you have any sort of reference table or formula to convert a HDOP value into HEPE (horizontal estimated position error) in meters?

Something along the lines of:

  • HDOP 2 = 1 meter HEPE (meaning there’s a 95% confidence that the location reading is within a 1 meter radius of the lat/lon)
  • HDOP 5 = 50 meters HEPE (meaning there’s a 95% confidence that the location reading is within a 100 meter radius of the lat/lon)
  • HDOP 10 = 300 meters HEPE (meaning there’s a 95% confidence that the location reading is within a 300 meter radius of the lat/lon)
  • HDOP 20 = 5000 meters HEPE (meaning there’s a 95% confidence that the location reading is within a 5000 meter radius of the lat/lon)

Hi Philip Schlesinger,

In GNSS module, we take EPE (estimated postion error) for reference. You will have estimated postion error(unit: meter) in direction x,y, and z.

Unfortunately, we don’t have formula to convert HDOP to EPE. EPE is calculated by raw GNSS observation data. You can take what I discribed about HDOP for rough reference.

Best regards.

Hi @Raphael-Q – I’m looking at “EC2x&EG2x&EG9x&EM05 Series GNSS Application Note, LTE Standard Module Series, Version 1.4, Data 2023-05-08” – and I don’t see a way to get the raw EPE when getting a location fix. I’m looking at “2.6. AT+QGPSLOC Acquire Positioning Information”. Is there another AT call in a different reference I should be using?


Hi Philip,

EG2x doesn’t support EPE. The calculation of EPE mainly rely on chipset but not outside the module. EG2x doesn’t support GNSS raw data either.

Best regards.

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