Proposal: Coarse GPS locations

[fsedarkalex]

I would like to propose adding coarse GPS locations.

To make it least effort, I'd suggest the following:

In GPS settings add an option "coarse" and rename "on" to "exact".

Whenever the device is using the GPS location, it will calculate and round the lon/lat coordinate to a precision which will effectively cause a worldwide "grid" of approximately 5x5km cells (at equator), up to 5x8km cells (near poles).

I used ChatGPT to create such a calculation code:

#include <math.h>

#define GPS_COARSE_GRID_DEG 0.05
#define GPS_COARSE_MIN_FACTOR 0.7

static inline double lat_factor(double lat)
{
    double f = 1.0 - 0.2 * (fabs(lat) / 90.0);  // linear approximation
    return (f < GPS_COARSE_MIN_FACTOR ) ? GPS_COARSE_MIN_FACTOR : f;
}

double snap_lat(double lat)
{
    return round(lat / GPS_COARSE_GRID_DEG ) * GPS_COARSE_GRID_DEG ;
}

double snap_lon(double lon, double lat)
{
    double step = GPS_COARSE_GRID_DEG / lat_factor(lat);
    return round(lon / step) * step;
}

I made this simple on purpose. Of course, there is more and nicer options but I think we should stick to the basics and keep it simple.

//Edit: Maybe we should also add a hysteresis. The Location should only update, when the device has actually moved 500m (on the exact location) or more. This prevents jumping if it is physically at a cell border.

[mrlmuk]

I have proposed a similar idea before, using the decimal places to increase or decrease the precision and changing the default from 0.000001 (11cm) to 0.001 (111meters).

Here are a few more related posts which would help battery life, allow better tracking if devices like T1000/RakTag and provide an initial NTP/RTC time clock update to repeaters.

[Feature Request] Position - add the ability to vary the precision #870
Add optional GPS obfuscation / reduced precision to mitigate unintended tracking #1265

[Feature Request] GPS polling at 1 Hz is wasteful — interval & motion-based activation needed #873
moko smart/WisMesh Tag needs ability to always send position #866

[fsedarkalex]

I see, precision is the word I should have searched for 😆