Values for GPS are inexact

[ovidiuvisan]

Given 57 15' 23.31" N as latitude, converted to decimal should output 57.256475 not 57.256474

only when i converted back to GPS coordinates the problem becomes clear: 57.256475 == 57 15' 23.31" 57.256474 == 57 15' 23.3" (converted using http://www.onlineconversion.com/map_decimaldegrees.htm) seems you are taking in account only the first digit after the . Same issue on Longitude. Can you please fix it, to have the same output as exiftool?

[rwcarlsen]

Could you provide a photo (or link to one) that exemplifies the problem?

[ovidiuvisan]

Sure, this picture can be used.

exiftool -c "%.6f degrees" -gps:GPSLatitude DSCN0035.JPG GPS Latitude : 57.242143 degrees

and using goexif: 57.24214

same for Longitude

exiftool -c "%.6f degrees" -gps:GPSLongitude DSCN0035.JPG GPS Longitude : 111.401488 degrees

and using goexif: 111.40149

if you take both values for Latitude for example and convert them back into GPS degrees, minutes, seconds with http://www.onlineconversion.com/map_decimaldegrees.htm, the problem will become clear, goexif takes in account only 1st decimal in seconds, 57 14' 31.7" instead of 57 14' 31.71". It should take all the decimals in account.

[rwcarlsen]

I don't think there is anything wrong with goexif. The exif GPS tag data is returned in Go's big.Rat format. The raw Lat-Long data I get from the sample file is:

GPSLatitude: ["57/1","14/1","31716/1000"]
GPSLongitude: ["111/1","24/1","5358/1000"]

You will want to do sth like this (except handle all the errors):

    fname := "gps.jpg"
    f, _ := os.Open(fname)
    x, _ := exif.Decode(f)

    lat, _ := x.Get(exif.GPSLatitude)
    deg, _ := lat.Rat(0).Float64()
    min, _ := lat.Rat(1).Float64()
    sec, _ := lat.Rat(2).Float64()
    floatLat := deg + min/60 + sec/3600
    fmt.Printf("latitude: %v\n", floatLat)

That gives me this output:

latitude: 57.24214333333333

[ovidiuvisan]

i see, thank you for the example. This will work fine.