Distance calculation "dist": obviously wrong or inaccurate about gw HOT 5 CLOSED

Reminder that EY is running 0.3.79

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yes, I know. 0.3.79 was based on choral's distance calculation. Found the problem. Will be test driving later.

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I was thinking we could do this really nicely, and add distance between two measurements as well as total travelled distance, if you feel like it.

From the dataset I handed you earlier, these are two 't' points taken near Kassel this morning:

{"_type":"location","t":"t","lon":"9.502427","lat":"51.240769","vel":"134.620028"}
{"_type":"location","t":"t","lon":"9.48138","lat":"51.226019","vel":"129.940024"}

According to this page I covered a distance of 2199 meters (see screenshot)

Using a haversine formula, I get the result: 2.19802314367 km which is close enough.

#!/usr/bin/env python

# from http://stackoverflow.com/questions/4913349/

from math import radians, cos, sin, asin, sqrt

def haversine(lon1, lat1, lon2, lat2):
    """
    Calculate the great circle distance between two points 
    on the earth (specified in decimal degrees)
    """
    # convert decimal degrees to radians 
    lon1, lat1, lon2, lat2 = map(radians, [lon1, lat1, lon2, lat2])

    # haversine formula 
    dlon = lon2 - lon1 
    dlat = lat2 - lat1 
    a = sin(dlat/2)**2 + cos(lat1) * cos(lat2) * sin(dlon/2)**2
    c = 2 * asin(sqrt(a)) 

    # 6367 km is the radius of the Earth
    km = 6367 * c
    return km 

lon1 = 9.502427
lat1 = 51.240769

lon2 = 9.48138
lat2 = 51.226019

distance = haversine(lon1, lat1, lon2, lat2)
print distance, " km"

We could add something like this to the JSON payload:

{ "mov" : "2198", "dist" : <total since reboot> }

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The problem is not the haversine calculation (although there is no arcsin in javame), but the elimination of movements while stationary, e.g. my gw sitting on my desk moved 23 km in 3 hours.

Will do

{ "dist" : "<distance since last location published>", "trip" : "<incremental distance since reboot>" }

and treat both as optional fields.

from gw.

solved using the correct haversine formula and calculation between GPS messages / mqtt messages.

from gw.