MacTelChat - View Single Post - Enable the hidden iPhoto Google Maps geotagging feature

javester · 09:07 PM

Actually, after double checking the GPS coords, its iPhoto that has a problem.

I entered the coordinates in 38 deg 55' 55.23" N, 74 deg 57' 32.48" W with an altitude of 2 metres using ExifTools, and iPhoto somehow mangled the coordinates to 38.00 deg 55.00' 1.47 N 74 deg 57.00' 1.76.00" W, Altitude 1 metre when I imported it.

The coords on the left are the ones I manually entered with ExifTools. The one on the right is what iPhoto displayed.

Right off the bat, the altitude was just wrong.

Also, the way iPhoto displays the GPS coordinates is a giveaway that the GPS code is still in a rough state - the GPS coords all have decimal points, which is a geographic coordinate no-no.

According to the Google Earth User Guide, there are three widely acception GPS notation conventions:

Decimal Degrees (DDD) In this notation, decimal precision is set in the degree coordinate. For example, 49.11675953666N.
Degrees, Minutes, and Seconds (DMS). In this notation, decimal precision is set in the seconds coordinate. For example, 49 7'20.06"N.
Degrees, Minutes with Decimal Seconds (DMM) In this notation, decimal precision is set in the minutes coordinate. For example, 49 7.0055722"N. (Here, 20.06 seconds above is divided by 3600 to get the decimal minute value for 20.06 seconds.)

Notice that only the last figure in each convention has decimal precision. You simply can't have decimal precision for all the units. It just doesn't make sense.

In addition, I suspect iPhoto's GPS conversion logic has some NSDecimal rounding/precision problems, most probably, the part that reads EXIF tags, since it properly created the DD version (38.917075, -74.950489) which it passed to Google Maps (and GM properly rendered. GIGO - Garbage In, Garbage Out)

Just to be sure, I also double-checked ExifTools to see if it was encoding the GPS EXIF data properly. I downloaded the free Opanda Exif Viewer and it confirmed ExifTools' GPS encoding.

It's a legitimate bug since the GPS fields in the InfoPanel are not hidden unlike the Google Map linking button.

I'll also try to see if I can enter the GPS EXIF tags with Aperture 1.5 when I pass by the Apple Store later.

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javester Administrator Status: Offline Posts: 209 Join Date: Mar 2006	Why Google Maps marked the location offshore.. (Classic GIGO) - 10-04-2006, 06:10 PM Actually, after double checking the GPS coords, its iPhoto that has a problem. I entered the coordinates in 38 deg 55' 55.23" N, 74 deg 57' 32.48" W with an altitude of 2 metres using ExifTools, and iPhoto somehow mangled the coordinates to 38.00 deg 55.00' 1.47 N 74 deg 57.00' 1.76.00" W, Altitude 1 metre when I imported it. The coords on the left are the ones I manually entered with ExifTools. The one on the right is what iPhoto displayed. Right off the bat, the altitude was just wrong. Also, the way iPhoto displays the GPS coordinates is a giveaway that the GPS code is still in a rough state - the GPS coords all have decimal points, which is a geographic coordinate no-no. According to the Google Earth User Guide, there are three widely acception GPS notation conventions: Decimal Degrees (DDD) In this notation, decimal precision is set in the degree coordinate. For example, 49.11675953666N. Degrees, Minutes, and Seconds (DMS). In this notation, decimal precision is set in the seconds coordinate. For example, 49 7'20.06"N. Degrees, Minutes with Decimal Seconds (DMM) In this notation, decimal precision is set in the minutes coordinate. For example, 49 7.0055722"N. (Here, 20.06 seconds above is divided by 3600 to get the decimal minute value for 20.06 seconds.) Notice that only the last figure in each convention has decimal precision. You simply can't have decimal precision for all the units. It just doesn't make sense. In addition, I suspect iPhoto's GPS conversion logic has some NSDecimal rounding/precision problems, most probably, the part that reads EXIF tags, since it properly created the DD version (38.917075, -74.950489) which it passed to Google Maps (and GM properly rendered. GIGO - Garbage In, Garbage Out) Just to be sure, I also double-checked ExifTools to see if it was encoding the GPS EXIF data properly. I downloaded the free Opanda Exif Viewer and it confirmed ExifTools' GPS encoding. It's a legitimate bug since the GPS fields in the InfoPanel are not hidden unlike the Google Map linking button. I'll also try to see if I can enter the GPS EXIF tags with Aperture 1.5 when I pass by the Apple Store later. Last edited by javester : 10-04-2006 at 09:07 PM.