Each aerial image taken by a drone has some exif data. What does that exif data signify?
There are latitude / longitude and altitude values mentioned. What does this data signify?
Does this signify the ground location as seen in the image?
Or does this signify the actual location (aerial) from where the image was taken?
EXIF is just a data format. Most cameras, including drone's, attach some information to each photo taken.
The amount of this information and its specifics varies greatly. There are hundreds or even thousands of different tags that the camera can provide. All of them are optional, but some of them are very common and are present in nearly every photo/camera, such as "Date taken", "Exposure time" etc. The camera model is nearly always attached as well (as a text string). These items are well documented and can usually be unambiguously interpreted.
On the other hand, a big chunk of tags are camera-specific "maker notes", and their interpretation will depend on the camera manufacturer. Some of them are well documented, some were reverse-engineered, but more are being added with each new camera. The popular ExifTool is perhaps the most comprehensive EXIF parser/manipulator (albeit command-line). Its documentation has description of most known tags.
Most decent image viewing software (including online services) have the ability to display EXIF info alongside with the image. The more generic ones can only display the most common tags, while the more specialised software can decode most tags, including Maker Notes.
As for the location data, it's fairly comprehensive in theory. The standard has provision for the camera as well as the subject location. However, in practice, I've only seen the camera location being filled. It is much more difficult and ambiguous to ascertain the exact subject location, especially for landscapes.
For example, this is what comes from a DJI Mavic Pro:
GPS Altitude : 324.9 m Above Sea Level GPS Latitude : 37 deg 35' 30.81" S GPS Longitude : 144 deg 54' 13.29" E
(Each piece of info here actually uses two EXIF tags: the data and the reference, such as "Above Sea Level"). The altitude here is also the camera (i.e. drone) altitude; it is not height above the ground.
In addition, there is a bunch of DJI-specific tags, which can help you to pinpoint the approximate subject location if you really want to:
Speed X : -0.30 Speed Y : -0.10 Speed Z : +0.00 Pitch : -0.60 Yaw : +113.60 Roll : -3.00 Camera Pitch : -9.50 Camera Yaw : +113.70 Camera Roll : +0.00
Interestingly, DJI doesn't write the barometric height, even though it knows it (and can write it to the srt subtitles to the video).
Of course, your drone can have a different set of data. However, the basic GPS data (i.e. camera location) is fairly universal.
Hi Mate EXIF is the Acronym for Exchangeable Image File, a format that is a standard for storing interchange information in digital photography image files using JPEG compression, therefore is widely used in digital photography and not only in pictures taken with drones. Almost all new digital cameras use the EXIF annotation, storing information on the image such as shutter speed, exposure compensation, F number, what metering system was used, if a flash was used, ISO number, date and time the image was taken, whitebalance, auxiliary lenses that were used and resolution. Some images may even store GPS information so you can easily see where the images were taken. Thanks to Prof TsuruZoh Tachibanaya. https://www.media.mit.edu/pia/Research/deepview/exif.html we have an excellent document reporting EXIF specification. Moreover Latitude and Longitude report the actual geografical location from where the image was taken (the camera's location). This opens a wide discussion about GEOTAGGING that in summary is the about including the geographic location related to the picture that has been taken. A very interesting document about EXIF GPS Geotagging is here: https://www.ridgesolutions.ie/index.php/2015/03/05/geotag-exif-gps-latitude-field-format/
