GPS fixing problem!

kamkar1

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Dash Cam
Lukas LK-7500G / Innovv C3 / mobius / G1W / SG9665GC & more
#21
I had a feeling, been prepping my living room window, and sourcing a 230 V timer to simulate drive sessions.
 
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Kobra

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QVIA AR790 2CH
#22
Hi everyone, it's quite awhile. Lately, I have tried some experiments to improve the ability of GPS signal reception of the dashcam and wanna share my experience/findings with you guys.
I recently bought a set of GPS signal repeater( receiver installed on the car roof and transmitter put inside the car) which made the GPS signal inside the car obviously stronger monitored by an app called GPS test and the following are the consequence.
1. TTFF seems to be significantly shortened to few minutes. (Earlier - a few hours to days)
2. GPS LED of the dashcam turns blue and stays blue quite more steadily. (Earlier - changed from blue and red quite more often)
3. GPS LED stays blue though driving near or under overpasses or bridges. (Earlier - immediately turned red when getting near overpasses or bridges)

However, from my additional observation I found that
- Placing spots of the transmitter in order to give stable GPS signal are limited. Now I have placed it on spot on dashboard and below the dashcam after trying several spots.
- Not proper spot even cause no GPS signal.

Please feel free to comment or share your helpful info and related experience. More than happy to hear that.
 
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Kobra

New Member
Joined
Nov 30, 2017
Messages
26
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Country
Thailand
Dash Cam
QVIA AR790 2CH
#23
Hi everyone, it's quite awhile. Lately, I have tried some experiments to improve the ability of GPS signal reception of the dashcam and wanna share my experience/findings with you guys.
I recently bought a set of GPS signal repeater( receiver installed on the car roof and transmitter put inside the car) which made the GPS signal inside the car obviously stronger monitored by an app called GPS test and the following are the consequence.
1. TTFF seems to be significantly shortened to few minutes. (Earlier - a few hours to days)
2. GPS LED of the dashcam turns blue and stays blue quite more steadily. (Earlier - changed from blue and red quite more often)
3. GPS LED stays blue though driving near or under overpasses or bridges. (Earlier - immediately turned red when getting near overpasses or bridges)

However, from my additional observation I found that
- Placing spots of the transmitter in order to give stable GPS signal are limited. Now I have placed it on spot on dashboard and below the dashcam after trying several spots.
- Not proper spot even cause no GPS signal.

Please feel free to comment or share your helpful info and related experience. More than happy to hear that.
Update:
According to the test above and some supporting info, I may analyse and conclude as follow:
The GPS module is composed of many parts. However, major parts that may be considered directly impact to GPS signal reception and GPS data are such as GPS chip (for GPS process), GPS antenna (for Signal reception), and GPS battery(for maintaining the GPS data so called "Ephemeris data" while no power supplied to the dash cam and GPS module i.e. dash cam off).

1. Since the GPS is working, GPS chip is proven to be fine.
2. From the result of experiments, installing GPS repeater helps shorten the time for GPS lock due to stronger GPS signal inside the car.
- This may be assumed that GPS signal reception ability or sensitivity is considerably lower than that of LK-7950WD (my past dash cam model in the same car, tint, dash cam installing spot, driving location, etc.), though it's supposed to be the same as you earlier mentioned in your e-mail.
- The GPS part that may cause the situation is assumed as GPS antenna.
3. After parking the car with the dash cam off for a few days, then starting the car engine again with the dash cam on, until getting the GPS lock it takes long time such as 10 - 20 minutes, which this seems to be TTFF (Time-To-First-Fix)
- If my understanding is correct, when using the dash cam for the first time, it will take quite long time (e.g 10 minutes or more) to get the GPS lock, but later on it's supposed to be quicker though the dash cam is off for a few days because the GPS data stored in the GPS memory is still maintained due to the GPS battery.
Thus, this incident may be assumed that GPS battery is somehow failed?

Your comments and feedback are always welcome. Please feel free to share.
 
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Kobra

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Nov 30, 2017
Messages
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Thailand
Dash Cam
QVIA AR790 2CH
#25
Update:
According to the test above and some supporting info, I may analyse and conclude as follow:
The GPS module is composed of many parts. However, major parts that may be considered directly impact to GPS signal reception and GPS data are such as GPS chip (for GPS process), GPS antenna (for Signal reception), and GPS battery(for maintaining the GPS data so called "Ephemeris data" while no power supplied to the dash cam and GPS module i.e. dash cam off).

1. Since the GPS is working, GPS chip is proven to be fine.
2. From the result of experiments, installing GPS repeater helps shorten the time for GPS lock due to stronger GPS signal inside the car.
- This may be assumed that GPS signal reception ability or sensitivity is considerably lower than that of LK-7950WD (my past dash cam model in the same car, tint, dash cam installing spot, driving location, etc.), though it's supposed to be the same as you earlier mentioned in your e-mail.
- The GPS part that may cause the situation is assumed as GPS antenna.
3. After parking the car with the dash cam off for a few days, then starting the car engine again with the dash cam on, until getting the GPS lock it takes long time such as 10 - 20 minutes, which this seems to be TTFF (Time-To-First-Fix)
- If my understanding is correct, when using the dash cam for the first time, it will take quite long time (e.g 10 minutes or more) to get the GPS lock, but later on it's supposed to be quicker though the dash cam is off for a few days because the GPS data stored in the GPS memory is still maintained due to the GPS battery.
Thus, this incident may be assumed that GPS battery is somehow failed?

Your comments and feedback are always welcome. Please feel free to share.
Update:

Additional observation: When a smartphone is placed near the GPS antenna inside the car, the observed GPS signal (monitored by GPS Test app) was likely to drop due to the possible interference from the smartphone. Thus, the smartphone should be placed not close to the antenna.
 
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Kobra

New Member
Joined
Nov 30, 2017
Messages
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Dash Cam
QVIA AR790 2CH
#26
Update:

Additional observation: When a smartphone is placed near the GPS antenna inside the car, the observed GPS signal (monitored by GPS Test app) was likely to drop due to the possible interference from the smartphone. Thus, the smartphone should be placed not close to the antenna.
UPDATE:

The photo below is the GPS module of AR790 at the base attached to the windshield.
The base as the housing for the GPS module is easily opened by unscrewing.
Findings:
1. the GPS module used is ublox 6
2. GPS antenna
3. Backup battery
AR790 GPS Module.jpg
 
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