Improve arrival mathematics

[marikavertzonis]

Predictive filtering algorithms should be used to improve navigation and arrival mathematics. Consider Kalman filtering to improve arrival https://en.wikipedia.org/wiki/Kalman_filter

[marikavertzonis]

Before introducing complex calculations, basic arrival logic has been implemented. In version 1.0.85 ithe following logic is used, depending on which is reached first:

• when the user gets with 20m of the target eg: this is most apparent if the device has gone to sleep and you wake the device, if it wakes and finds itself within 20m of the target, it will 'arrive', or,
• relative to speed of travel using this equation: 3 * (currentSpeedFromDevice / 1.4). This assumes an average walking speed of 1.4 m/s and therefor if walking, you will see the arrival notification when you are 3 sec away from the target.

[marikavertzonis]

Now that the location accuracy is shown (as of 1.1) it seems odd that i 'arrive' when i get within 20m of the location, even when my location is being reported with an accuracy of 5m.
If horizontal accuracy is available, we should refine our arrival logic to take it into account. Something like:

Show as 'arrived' IF (2 x Horizontal Accuracy) < 20m.

2 x horizontal accuracy would allow for the worst case scenario that you are furthest away from the destination, within the horizontal accuracy. See below diagram for explanation

[defiantgoat]

See #59. Arrival logic has been disabled for version 2.0. However, this can be revisited and finessed if arrival logic is re-enabled in the app.

[dominikargast]

Rev e10da17 should have been assigned to #31

[dominikargast]

@marikavertzonis I've reinstated arrival logic based on GPS accuracy. The current scheme is very simple and most likely needs to be improved. Feedback from real world usage is required.

Test with build 3.0.27

[IsmaelInRedlands]

Tested 3.0.27 today on iOS while riding a bicycle.
Two issues:

• App believes destination has been reached while still away from it (too early).
• App cleans up the destination set on arrival.

The video below shows the test. My destination was my red car. The app thought I had arrived when I was still about 100 meters away from the car.
Tested with built-in location (no GNSS receiver) but with a reported accuracy of around 6 meters

http://www.youtube.com/watch?v=2EfoFCXjN9k

[IsmaelInRedlands]

Two new tests on 3.0.27

While driving:

• App thought I was at destination around 500m before I arrived.

While walking:

• Reasonable (for the precision of the built-in GPS on iPhone). See video: https://www.youtube.com/watch?v=9Aw7SiG2ufg

Some thoughts:

• From the tests above it looks like the speed matters: Walking is reasonable, Bicyle arrives 100m before destination and by car 500m before destination.
• I wonder why we consider speed at all. Even while driving my car I eventually reduce speed to walking speed when I am about to arrive to destination.
• It feels to me like even in the walking test the app anticipated arrival way too early.
• I will test next arrival with GNSS receiver.

[dominikargast]

@marikavertzonis @IsmaelInRedlands Arrival logic has been improved. Please test with build 3.0.28

[marikavertzonis]

Testing with 3.0.28 on ios (with external gps) and 3.0.29 on android (with internal position source). At walking pace, i 'Arrive' at a distance that corresponds with my accuracy (very nice). More testing tbc.

[IsmaelInRedlands]

3.0.28 Built-in GPS on iPhone. 2 Tests with car. Looking good.

• https://www.youtube.com/watch?v=qWaxaied8ak
• https://www.youtube.com/watch?v=r0cuJl-Xg9E
  1 test walking. Looks good.
• https://www.youtube.com/watch?v=KaOWoPvSOdI

[dominikargast]

@marikavertzonis @IsmaelInRedlands I've added some tweaks to the arrival logic:

• A status message should appear if you reach your destination within the next 30 seconds at the current speed.
• If you've arrived and start to move away from your destination again, guidance will resume.
• If the compass is in use, a compass icon will appear in the top left corner (see Inform the user that the compass is being used #90).

Please test with build 3.0.31 and let me know if these features are useful/work as intended.

[marikavertzonis]

Testing with 3.0.31 on iphone 8 and pixel 2 at walking and driving pace. the arrival details really pertain to walking pace. this is good. if you're driving, you stop when approaching the site and get out and walk the final part. If there are specific driving arrival requirements, these should be separated into a new issue (or perhaps added to #82)

In this build,

• see 'approaching' message that corresponds to the expected arrival location
• arrival symbol appears once you are within the reported accuracy of the device
• if you then leave the arrival location, you get the 'approaching' messages again (but with increasing time and distance - as expected)