Improved docs

methodology.md

@@ -58,13 +58,18 @@ Source code is available at [src/icao_to_trace.rs](./src/icao_to_trace.rs).
 This is performed automatically by the computer program. A leg is defined in this methodology
 has a continuous sequence of ADS-B positions in time where the aircraft is flying.
 
-The aircraft at a given segment between two ADS-B positions is considered grounded (not flying) when either:
-* both positions are on the ground
-* the time between these positions is > 5m and the aircraft is below 10.000 feet
+The aircraft at a given segment between two ADS-B positions is considered grounded (not flying) when any of:
+1. both positions are on the ground
+2. the time between these positions is > 5m and any of the positions is below 10.000 feet
+3. the time between these positions is > 10h
 
-The latter condition is used to mitigate the risk that ADS-B receivers sometimes
+Condition 1. is the normal case where ADS-B signal was received when the aircraft landed. 
+Condition 2. is used to mitigate the risk that ADS-B receivers sometimes
 do not receive an aircraft's signal when the aircraft is at low altitude.
-When this happens for more than 5m, we consider that the aircraft approached and landed.
+Condition 3. is used to mitigate situations where the aircraft enters regions
+of low ADS-B coverage (e.g. central Africa) while flying and then returns flying
+(sometimes days later), which should be intepreted as the aircraft being flying for the whole
+time.
 
 Source code is available at [src/legs.rs](./src/legs.rs).
 

src/legs.rs

@@ -47,6 +47,7 @@ fn grounded_heuristic(prev_position: &Position, position: &Position) -> bool {
         (&prev_position, &position),
         (Position::Flying { .. }, Position::Flying { .. })
             | (Position::Flying { .. }, Position::Grounded { .. })
+            | (Position::Grounded { .. }, Position::Flying { .. })
     );
     let lost_close_to_ground = position.datetime() - prev_position.datetime()
         > time::Duration::minutes(5)

tests/it/main.rs

@@ -70,18 +70,14 @@ async fn legs(
         .collect::<Vec<_>>();
     positions.sort_unstable_by_key(|p| p.datetime());
 
-    log::info!("Computing legs {}", icao_number);
-    let legs = flights::legs(positions.into_iter());
-
-    // filter by location
-    Ok(legs)
+    Ok(flights::legs(positions.into_iter()))
 }
 
+/// Verifies that condition 2. of `M-4` is correctly applied.
+/// https://globe.adsbexchange.com/?icao=458d90&lat=53.265&lon=8.038&zoom=6.5&showTrace=2023-07-21
 #[tokio::test]
-async fn multi_day_legs() -> Result<(), Box<dyn Error>> {
+async fn ads_b_lost_on_ground() -> Result<(), Box<dyn Error>> {
     let legs = legs(date!(2023 - 07 - 21), date!(2023 - 07 - 23), "458d90", None).await?;
-
-    // same as ads-b computes: https://globe.adsbexchange.com/?icao=458d90&lat=53.265&lon=8.038&zoom=6.5&showTrace=2023-07-21
     assert_eq!(legs.len(), 6);
     Ok(())
 }
@@ -93,7 +89,8 @@ async fn case_459257_2023_12_17() -> Result<(), Box<dyn Error>> {
     Ok(())
 }
 
-/// Case of losing signal for 2 days mid flight.
+/// Verifies that condition 3. of `M-4` is correctly applied.
+/// Case of losing signal for 2 days mid flight while traveling to central Africa.
 /// https://globe.adsbexchange.com/?icao=45dd84&lat=9.613&lon=22.035&zoom=3.8&showTrace=2023-12-08
 #[tokio::test]
 async fn case_45dd84_2023_12_06() -> Result<(), Box<dyn Error>> {