hmm.. Some of the wingspan length is due to the winglets on the -700, where that particular -300 hadn't been retrofitted (I'm assuming that the -300 is #1).
Generally, Google Maps' aerial satellite images aren't exactly an accurate method of judging things like this. Simply by looking at the image linked in the original post, you can tell that a few things about the image are distorted. Some of the yellow lines painted on the taxiways are cut and don't line up properly. Also, the second aircraft (top) has it's wingtip cut-off (our left when looking from above), but the shadow of the winglet it still clearly visible.
As all Southwest -700's have had winglets for several years now (as do majority of the "newer" -300's that they plan to keep for a few more years), we can tell for sure that the aircraft at the top is a -700 (based on the appearance of the top of the wings as well as the wingspan). The aircraft at the bottom is definitely a -300 without winglets as it's too long to be one of their 25 -500's.
Either way, it would still be easy to tell a -300 from a -700 from above based on the wingspan (with or without winglets installed) alone. The wingspan on a -300 is 94ft 9in (no winglets), while the wingspan on a -700 is 117ft 5in (with winglets).
However.. you can definitely tell the difference between the -300 and -700 by the fuselage length. The -700 is visibly longer than the -300, and getting an overhead view is the best way to tell that.
Respectfully, you are incorrect there. The overall length of a -300 is 109ft 7in, while a -700 has an overall length of 110ft 4in - which is only a difference of nine inches.
Google Maps' ruler tool (for what it's worth here) shows both aircraft (from radome to APU exhaust) in this satellite image to be roughly 110ft in length. This would make sense as the actual difference is only, as stated above, nine inches.
If, for example, we were looking at a -300 and a -800 from above, that would be much easier to do as there is a difference of nearly 20 feet.
For reference, here are the overall lengths and wingspans of the various 737 models that have been widely used in commercial service (not including BBJ variants):
737-200 and 737-200/Advanced
Overall length....: 100ft.
Wingspan..........: 93ft.
737-300
Overall length....: 109ft. 7in.
Wingspan..........: 94ft. 9in. (102ft. 1in. with winglets)
737-400
Overall length....: 119ft. 6in.
Wingspan..........: 94ft. 9in.
737-500
Overall length....: 101ft. 8in.
Wingspan..........: 94ft. 9in. (102ft. 1in. with winglets)
737-600
Overall length....: 102ft. 6in.
Wingspan..........: 117ft. 7in.
737-700
Overall length....: 110ft. 4in.
Wingspan..........: 117ft. 5in. (112ft. 7in. without winglets)
737-800
Overall length....: 129ft. 6in.
Wingspan..........: 117ft. 5in. (112ft. 7in. without winglets)
737-900
Overall length....: 138ft. 2in.
Wingspan..........: 117ft. 5in. (112ft. 7in. without winglets)
(Data taken from PDF documents available on Boeing's website)
The thing that always helped me out was the emergency exits. It's easy to tell the difference between the models by the emergency exit doors, but hard to tell between the -300s and -700s, as they are nearly in the same place. The -800s and -900s are the easiest (2 exits over the wing).. There are others, but those are the easiest that I've been able to tell.
The over-wing exit doors on the -300 and -700 are in the same location. The exterior differences visible to the naked eye (from a distance) are negligible, unless you happen to see them open. The -300's exit doors completely detach from the aircraft, while the -700's doors open upward and remain attached to the aircraft.
There are quite a few ways to tell a -300 from a -700 when you're looking at them from the ground (or underneath), but that's another discussion for another time.
Matt
(KBNA)
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