Purpose of chapter: to describe how utilize presence of Metadata in photos to connect these to tracks. Consider it an extension of the Photo chapter.
Local TOC
Overview
When taking a photo with the Camera App, an image is captured through the lens and saved in the Cameraroll, together with information on camera settings, creation date and possibly coordinates - if available. These data are collectively designated Metadata - part of which is sometimes called Geotag data.
The latter two pieces of the Metadata (creation date & coordinates) - only these are considered in this App - can be fetched from the Cameraroll if:
- Metadata existance requirements are met
- Metadata access requirements are met
These photo Metadata can then be utilized to localize a 'nearest plot' on a track, and connect the plot to the photo - making it accesible via special yellow eventpins on the Map. And from other places.
Linking to a photo is done via an event attached to the nearest plot. Such event can be an existing event, or an Autogenerated event,
This can be illustrated with the entity-relationship diagram below (arrows represent one-to-many or one-to-one relationship):
+---------------+
! !
! Track !
! !
+---------------+
! !
v v
+---------------+ +---------------+
! ! ! !
! Photo ! ! Plot !
! ! !(aka Location) !
+---------------+ +---------------+
! !
v v
+---------------+
! !
! Event !
! !
+---------------+
Throughout the manual the term track usually covers note - BUT connecting photos applies only to tracks.
Read the diagram like:
- a track has zero or more photos attached (added)
- a track has many plots attached (added)
- an event can be linked to one photo
- an event is linked to one plot
This chapter is focused on connectiong photos to historic tracks, which is probably the typical situation.
But everything written here also applies to a current track (the track that's being tracked) - though one should then concentrate on sailing, allowing occational use of the Camera. But: DON'T LET USE OF THE APP INTERFERE WITH YOUR NAVIGATION!
Alternative ways to connect a photo
As mentioned in the Shoot chapter, there are more ways to connect and localize a photo in relation to a track. They may be combined so consider them companions.
One way:
- capture a photo with the built-in 'Shoot' Camera while tracking
This is the most direct and simple way, but you must accept limited Camera functionality.
And if you in the Shoot Options Menu choose to Save to Cameraroll also? you must accept that a photo may be non-importable by DropBox and other storage providers (excluding Apple).
(The 'Shoot' way is not further dealt with in this chapter)
Another way:
- capture a photo with the iOS Camera App while or after tracking, and then:
- use the Photo Options Menu action: Add from Cameraroll action (using a 'connecting strategy')
This Camera you're familiar with. Capture as many photos as you like, and later pick the best or most relevant to connect to your tracks.
Finally, there is a Manually managing photo connections option.
Metadata existance
Correct settings are required. You can check or change your allowances as follows:
Go to Settings -> Privacy -> Location Services -> Camera:
First time use of a 'connect' Add Strategy
If you in Photo Options Menu action: Add Strategy -> select 'connect', then when you use the Photo Options Menu action: Add from Cameraroll action first time, you must authorize:
(Unless you already did authorize in Saving to Cameraroll also).
- and after tapping an iOS allowance settings dialog opens:
After completing your authorization, the Photos subpage reappears - with an action ready for use.
Should you have chosen the Don't Allow option, then will show:
Metadata access
After First time use of a 'connect' Add Strategy has been done, you can check or change your allowances as follows:
Go to Settings -> Privacy -> Photos -> Sailor Logbook:
Find nearest plot algorithm
With knowledge to a creation date & coordinates for a photo and a given track to connect to, the App tries to find a 'nearest plot' as follows.
First all plots are examined (mutual distance is max. 200 meter - not considering Resume last track situations):
- each plot with a time difference between its timestamp and photo creation date less than 2*60 seconds is examined
- distance between location of such a plot and the photo is calculated
- the smallest distance is determined:
- for plots with an event attached (type X)
- for plots without event attached (type Y)
Then it's determined if a smallest distance less than 100 meter (half of 200 meter) is found for plots of type X - if so, its' furher determined if this event is already connected to a photo or not, resulting in one of these:
- a) Ok: photo saved: - nearest plot with an event now linked to photo
- b) Photo saved, BUT connect failed
- c) Photo SKIPPED, as connect failed
b) applies to Add Strategy Try connect, and c) applies to Must Connect. Diagnosis for both is nearest plot with an event already was linked to a photo.
Otherwise it's determined if a smallest distance less than 100 meter is found for plots of type Y - if so, an autogenerated event is attached to the nearest plot, resulting in:
- d) Ok: photo saved: - a new autogenerated event is attached to nearest plot and now linked to photo
If none of the above succeeds, the result is:
- e) Photo saved, BUT connect failed
- f) Photo SKIPPED, as connect failed
e) applies to Add Strategy Try connect, and f) applies to Must Connect. Diagnosis for both is photo location not near any plot of the track: max. distance (100 meter) and / or max. time difference (2*60 seconds) exceeded.
If two photos are very close in time and location, adding them from the Cameraroll may result in one photo accepted, and the other declined - because both will connect to same plot. I.e. a 'first come, first served' situation. To avoid, pick photos from the Cameraroll that are not so close.
The rationale for prioritizing time difference (< 2*60 secs) is to ensure correct localization of photos when cruising back and forth near same positions on the same track. When for example on a round trip taking a photo leaving home port, and another returning.
Moving 100 meter in 2*60 seconds corresponds to a speed of 3 km/hour ~ 1.62 kn. So if you move slower than that and take a photo precisely between two plots on a straight line, connecting it will fail.
Cannot find nearest plot
When using a 'connect' Add Strategy, the Find nearest plot algorithm cannot be applied to a photo where no Metadata is found, or allowance to access Metadata wasn't given. The result is one of these:
- g) Photo SKIPPED: no Metadata found
- h) Photo SKIPPED: no Metadata access
This applies regardless of which of the two 'connect' Add Strategies that was selected.
Example
To illustrate the use of Add Strategy Must connect, a chronologically ordered sequence of screenshots follows.
Example, track before connecting photos
The Map below displays a walking trip, after return home - shown with a MapSet: Show eventpins Picker choice of All (slowest):
The two orange pins seen in the lower part represent user events.
Example, Cameraroll selection
The Photo Options Menu action: Add from Cameraroll action is then invoked, and 9 photos selected:
Note: the order in which the App processes the selected photos is unpredictable, though they are presented in reverse chronological order above (newest first). E.g. the big white house is actually processed after the big house to the left of the windmill!
This problem will be solved later, see Example, Photo subpage content after sort.
Example, Add from Cameraroll connect report
When the button above is tapped, return to the Photo subpage shows a 'connect report':
Except for one photo, everything went fine. The problem with photo 5 is, that a 'first come, first served' situation arose because a photo before number 5 was connected first.
Photo 1 and 4 were connected to existing events. The other each caused the creation of an autogenerated event.
Example, track after connecting photos
The walking trip is shown again, still with a MapSet: Show eventpins Picker choice of All (slowest):
One of the two orange pins now has turned yellow (the red arrow).
When the W/ photo or voice option is chosen, the Map displays as:
Besides yellow pins, also a green eventpin is shown: it represents the other of the two existing events, that were connected to. Green (and red) pincolor has priority over yellow.
Example, tapping a yellow eventpin
One of the yellow eventpins is tapped:
Tapping the Disclosure button opens the Action on Event menu (Map version):
Finally, tapping the action opens:
Example, Photo subpage content
The first four of the accepted photos are:
The big yellow M should be a big yellow MM here and in other not quite up-to-date screenshots.
- and the last four of the accepted photos are:
Example, Photo subpage content after sort
Because the order in which the App processes the selected photos is unpredictable. This is brought in ordern with the Photo Options Menu action: Sort by creation date action - hereafter the first four of the accepted photos are:
- and the last four of the accepted photos are:
The 8 photos are now chronologically ordered - i.e. in same order as on the Map - which is not influences by the sort. Ordering in Mailcomposer is as in the Photo subpage.
The MetaMap
You may have noticed a big yellow MM mark next to the title in the screenshots above - tapping one (it's a shortcut for the Action on Photo Menu action: MetaMap action) opens:
The (always enabled) navigation bar button opens the:
MetaMap Options Menu
Tapping its action opens the MetaMap Help pages.
The Info on Photo
You may also have noticed a big blue #E:1 mark next to the title - tapping one (it's a shortcut for the Action on Photo Menu action: Info opens:
The Events linking list identifies one event, to which the photo is linked. The same photo may be linked to more than one event, which will then make the list longer.
Manually managing photo connections
Sometimes you may need or want to manually connect a photo to a track, in order to present a photo in Map context. This may be because:
- automatic connection as described above fails
- some photos may have no or mismatching Metadata
- an already connected photo should be replaced
You must:
- have user events (made by New event ) or XtraEvent's to connect to
- have photos corresponding to these events, in time or content
- be able to identify both photo(s) and track(s) later, to match them
So, after having selected Add Strategy Don't connect and then using the action, enter a title for your photos to associate with.
Using the Photo Clb and the Event editor, you will be able to perform the task, with help from The Track mainpage with its:
- CurrMap button
- Action on current track menu
or - after tracking - for a given track in the Tracklist with its:
Sailor Logbook App manual - © Copyright 2018 CoaSoft LLC Denmark