Calculate GPS_DELAY_MS without Gps.Spd

Hi all , I own a GPS module that provides NMEA messages with latitude and longitude , but does not provide information about GPS.Spd , speed.
Now , I would be interested in calculating the GPS_DELAY_MS of this module and I have referenced this script :

The problem that this script almost solely uses the velocity to calculate the delay , and my module does not provide this information .
So I would like to ask you what other methods exist to calculate the delay in MS for modules that are lacking GPS.Spd and provide only lat and lng. Thank you

And also ,if you can confirm me that ArduPilot use this value as default value for delay for NMEA modules :

AP_GPS_NMEA.cpp : 
`bool AP_GPS_NMEA::get_lag(float &lag_sec) const
{
    switch (get_type()) {
#if AP_GPS_NMEA_UNICORE_ENABLED
    case AP_GPS::GPS_TYPE_UNICORE_MOVINGBASE_NMEA:
    case AP_GPS::GPS_TYPE_UNICORE_NMEA:
        lag_sec = 0.14;
        break;
#endif // AP_GPS_NMEA_UNICORE_ENABLED

    default:
        lag_sec = 0.2; // <---- default value 200 ms ?
        break;
    }
    return true;
}`

I know @tridge has partly developed this script , could he have some advice maybe ? Thanks
Maybe some ideas from other developers ?
@peterbarker
@rmackay9
@khancyr
Thanks !