Thread: [UX] GPS Speed Calibration for 64bit iGO Luna / NextGen

IGO Luna skin Pongo (32-bit) same situation.

Hello to all the participants and friends of this thread.
I thought I would participate in it and answer everyone, and I also had to find out and update myself as of today in the chatGPT, so I came up with the idea of ​​having the most accurate dialogue with him that I could and presenting it to everyone. I would like to point out that all the information he provided me is up-to-date in some parameters for use in Israel, but of course most of it is equivalent to any "sky in the world."

And here we go:

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FULL CONVERSATION TRANSLATION
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PART 1: VEHICLE SPEEDOMETERS AND POLICE DEDUCTIONS
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User: KWBS
Hello. I remember that car manufacturers used to calibrate car speedometers to show a speed X km/h higher than the actual speed. This was done so that if a driver is speeding, for example at 110 km/h, their real-world speed would actually be a constant X percent lower. Is this true?

AI:
Yes, that is absolutely correct. Car manufacturers intentionally calibrate the speedometer to display a speed HIGHER than the vehicle's actual speed.

The Main Reasons for This:
* International Legislation and Standards: European standards (which are also adopted in Israel) strictly forbid speedometers from showing a speed LOWER than the actual speed. The system is legally required to display a speed equal to or higher than reality.
* Allowed Margin of Error: According to the European standard (ECE-R39), the speedometer can display up to 10% plus 4 km/h more than the true speed. For example, at a real speed of 100 km/h, the dashboard can display up to 114 km/h.
* Legal and Manufacturer Protection: Car manufacturers protect themselves against lawsuits from drivers who might claim they received a speeding ticket due to the speedometer underreporting their speed.
* Physical Vehicle Variations: Tire diameter changes due to wear, low air pressure, or switching to new tires. An built-in upward bias ensures that even with a brand-new, slightly larger tire, the speedometer will not underreport the speed.

What Happens in Practice?
* In City Driving (around 50 km/h): The variance is usually minimal, around 2 to 4 km/h.
* In Highway Driving (around 110 km/h): The variance increases and can reach 5 to 10 km/h lower in reality.
* Checking Actual Speed: GPS devices (like navigation apps) measure speed based on location and time, making them far more accurate than the vehicle’s built-in speedometer.

To better understand your case, have you noticed a SPECIFIC DISCREPANCY in your car, or are you trying to AVOID A SPEEDING TICKET on a specific route?

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User: KWBS
No, I don't have a discrepancy in my car. I just recalled this during a conversation with friends. I also know that when a driver receives a ticket for "exceeding the speed limit," the police officer is supposed to automatically deduct X amount from the reading shown on the laser gun. This is done to establish beyond any doubt and with absolute certainty that the vehicle exceeded the speed limit...

AI:
SPOT ON, YOUR MEMORY IS COMPLETELY ACCURATE.

When a police officer measures a vehicle's speed using an enforcement device (such as a laser gun/MAMLAZ or a speed camera), the Israel Police is legally required to deduct a FIXED VALUE from the recorded measurement. This deduction is designed to neutralize the device's statistical margin of error, ensuring that the speed attributed to the driver in the ticket is definitive and beyond a reasonable doubt.

Current Deduction Rules in Israel:
* Laser Gun (MAMLAZ): 5 km/h is automatically deducted from the measurement displayed to the officer on the gun.
* Fixed Speed Cameras (A-3): 5 km/h is deducted for measured speeds up to 100 km/h, or 5% of the speed for measurements above 100 km/h.
* How does it look on the ticket? The officer is required to note both figures on the ticket as follows:
- "Measured Speed" (the number that appeared on the device).
- "Enforced Speed" (the final speed after deduction, which determines the fine and penalty points).

Numerical Example:
If you were driving on an intercity highway with a speed limit of 90 km/h, and the laser gun clocked you at 114 km/h:
1. The officer will automatically deduct 5 km/h.
2. The speed written on the ticket will be 109 km/h.
3. Meaning: An excess of 19 km/h over the limit, which triggers only a fine (250 ILS) with no penalty points.

Why Is This Done?
Courts in Israel have ruled that without this built-in deduction, drivers would have an easy basis to appeal the device's reliability due to minor technical hardware variances. The combination of the VEHICLE'S BUILT-IN VARIANCE (showing a higher speed than reality) along with the POLICE DEDUCTION (lowering the speed from the measurement) creates a double safety net for drivers against wrongful punishment.


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PART 2: GPS DISRUPTIONS AND CELLULAR TRIANGULATION
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User: KWBS
GPS will also misrepresent data when there are intentional military disruptions...
And GPS will "misreport" when the satellites are configured to provide "accuracy" based on a specific level of precision per meter that they determine...

AI:
You are absolutely right, and those are two very accurate and important points regarding the limitations of civilian navigation systems:

1. Intentional Military Disruptions (GPS Spoofing / Jamming)
When a military (such as the IDF or other militaries around the world) activates intentional GPS disruptions for defense purposes, the navigation app on your mobile phone completely loses its reliability:
* Location Spoofing: The military system broadcasts fake GPS signals that make the phone "think" it is somewhere else entirely (for example, drivers in Tel Aviv or Haifa whose Waze suddenly shows them they are in Beirut or Cairo).
* Impact on the App's Speedometer: Since the app calculates speed based on the change of position between points, the moment your location suddenly "jumps" hundreds of kilometers in a split second, the app’s speedometer malfunctions completely—it might show a speed of thousands of km/h, freeze at zero, or simply not display any speed at all.

2. Altering Satellite Accuracy (Selective Availability)
The second point you mentioned touches on history and the control exerted by the US government (which controls the GPS satellites):
* In the Past (Until 2000): The US military intentionally operated a mechanism called Selective Availability. This mechanism introduced intentional "noise" into the civilian signal, restricting the accuracy of civilian devices to a range of about 100 meters, while the military reserved centimeter-level precision for itself.
* Today: Although this mechanism was deactivated in 2000 by President Clinton (and modern satellites are designed without this capability), the US government still retains the technical capability to block or degrade the civilian signal in specific conflict zones (a capability known as Regional Denial).

THE BOTTOM LINE: During times of disruption or conflict, THE VEHICLE'S PHYSICAL SPEEDOMETER becomes your only reliable source, as it is a closed mechanical/electronic system that does not depend on signals from outer space.

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User: KWBS
One last point: when satellite GPS is down, mobile phone navigation software can, of course, still provide location and speed based on cellular towers. What kind of discrepancy or impact, for better or worse, does this have on how the vehicle's speed is displayed on the screen?

AI:
When the GPS signal is blocked or disabled, mobile navigation apps switch to relying on CELLULAR TRIANGULATION and Wi-Fi networks. In this scenario, THE IMPACT ON THE SPEED DISPLAY IS VERY POOR—THE DATA BECOMES COMPLETELY UNRELIABLE, AND MOST APPS WILL SIMPLY STOP DISPLAYING SPEED ALTOGETHER.

The reasons for this extreme discrepancy and its effects on the screen are:

1. A Drastic Drop in Accuracy (The Main Reason)
* With Satellite GPS: Location accuracy is within a few meters (about 3 to 5 meters). This makes it easy for the app to calculate a precise speed.
* With Cellular Triangulation: The accuracy of location based on cell towers ranges from 50 METERS (in dense urban areas with many antennas) to HUNDREDS OF METERS OR EVEN KILOMETERS (in open or intercity areas).

2. How Does This Affect the Speed on the Screen?
Since the app cannot use the GPS hardware component (which measures speed directly and accurately), it is forced to "guess" your speed using a simple calculation: the distance traveled divided by the time it took to travel it. This low level of accuracy creates two major issues:
* The "Jumping" Phenomenon (Crazy Speed or Zero): If the phone detects for a moment that you are at Tower A, and a second later it jumps to Tower B which is 300 meters away, the app will calculate that you traveled at an imaginary speed of hundreds of km/h. To prevent this confusion, companies like Google or Waze block the speed display when there is no stable GPS signal.
* Freezing or Disappearing Speed: In the vast majority of cases, once the GPS is disabled, the app will display a dashed line (-- km/h), freeze on the last captured speed, or completely remove the speedometer from the screen.
* Massive Delay (Lag): Even if the app tries to display an average speed based on switching between cell towers, the update will only happen once every few minutes rather than in real time, making the data entirely useless while driving.

Summary:
When GPS is disabled and navigation relies on cellular towers, the device is mostly trying to "save" the map and give you a general idea of where you are. THE GAP COMPARED TO REALITY BECOMES IMPOSSIBLE TO MEASURE, and your sole and authoritative source for knowing your speed is THE VEHICLE'S SPEEDOMETER.

I hope I was useful in using the above for you. Thank you...