Ref T778, improved "canLikelySkipNearGround" in airspace monitor

* use CAircraftIcaoCode::guessModelParameters as this gives us an impression of speed
* use "breakable" do/while block / fewer nested "if" levels

src/blackcore/airspacemonitor.cpp

@@ -1370,32 +1370,50 @@ namespace BlackCore
         if (callsign.isEmpty()) { return situation; }
 
         CAircraftSituation correctedSituation(allowTestOffset ? this->addTestAltitudeOffsetToSituation(situation) : situation);
-        bool canLikelySkipNearGround = correctedSituation.canLikelySkipNearGroundInterpolation();
         bool needToRequestElevation  = false;
-
+        bool canLikelySkipNearGround = correctedSituation.canLikelySkipNearGroundInterpolation();
-        if (!correctedSituation.hasGroundElevation())
+        do
         {
+            if (canLikelySkipNearGround || correctedSituation.hasGroundElevation()) { break; }
+
             // set a defined state
             correctedSituation.resetGroundElevation();
 
-            if (!canLikelySkipNearGround)
-            {
-                // fetch from cache or request
-                const CAircraftSituationChange changesBeforeStoring = this->remoteAircraftSituationChanges(callsign).frontOrDefault();
-
             // Check if we can bail out and ignore all elevation handling
             //
             // rational:
             // a) elevation handling is expensive, and might even requests elevation from sim.
             // b) elevations not needed pollute the cache with "useless" values
             //
+            if (canLikelySkipNearGround) { break; }
+
+            // Guessing gives better values, also for smaller planes
+            // and avoids unnecessary elevation fetching for low flying smaller GA aircraft
+            const CAircraftIcaoCode icao = this->getAircraftInRangeModelForCallsign(callsign).getAircraftIcaoCode();
+            if (!icao.hasDesignator()) { break; } // what is that?
+            if (!icao.isVtol())
+            {
+                // Not for VTOLs
+                CLength cg(nullptr);
+                CSpeed rotateSpeed(nullptr);
+                icao.guessModelParameters(cg, rotateSpeed);
+                if (!rotateSpeed.isNull())
+                {
+                    rotateSpeed *= 1.2; // some margin
+                    if (situation.getGroundSpeed() > rotateSpeed) { break; }
+                }
+            }
+
+            // fetch from cache or request
+            const CAircraftSituationChange changesBeforeStoring = this->remoteAircraftSituationChanges(callsign).frontOrDefault();
+
             if (!changesBeforeStoring.isNull())
             {
                 canLikelySkipNearGround = changesBeforeStoring.isConstAscending();
+                if (canLikelySkipNearGround) { break; }
             }
 
-                if (!canLikelySkipNearGround)
+            // we NEED elevation
-                {
             const CLength dpt = correctedSituation.getDistancePerTime(100, CElevationPlane::singlePointRadius());
             const CAircraftSituationList situationsBeforeStoring   = this->remoteAircraftSituations(callsign);
             const CAircraftSituation situationWithElvBeforeStoring = situationsBeforeStoring.findClosestElevationWithinRange(correctedSituation, dpt);
@@ -1472,10 +1490,8 @@ namespace BlackCore
                     Q_UNUSED(couldNotExtrapolate)
                 }
             } // gnd. elevation
-
+        }
-                } // can skip?
+        while (false);  // do we need elevation, find on
-            } // can skip?
-        } // have already elevation?
 
         // do we already have ground details?
         if (situation.getOnGroundDetails() == CAircraftSituation::NotSetGroundDetails)

src/blackmisc/aviation/aircrafticaocode.cpp

@@ -248,7 +248,7 @@ namespace BlackMisc
 
             // init to defaults
             CLength guessedCG      = CLength(1.5, CLengthUnit::m());
-            CSpeed guessedVRotate = this->isVtol() ? CSpeed::null() : CSpeed(70, CSpeedUnit::km_h());
+            CSpeed  guessedVRotate = CSpeed(70,   CSpeedUnit::km_h());
 
             const int engines = this->getEnginesCount();
             const QChar engineType = this->getEngineTypeChar().toUpper();
@@ -283,6 +283,16 @@ namespace BlackMisc
                         break;
                     }
                 }
+
+                if (engineType == 'J')
+                {
+                    // MIL Jets a bit faster
+                    if (this->isMilitary()) { guessedVRotate *= 1.20; }
+                    else if (this->matchesDesignator("CONC")) { guessedVRotate = CSpeed(199, CSpeedUnit::kts()); }
+                }
+
+                // VTOL
+                if (this->isVtol()) { guessedVRotate = CSpeed(0, CSpeedUnit::kts()); }
             }
             while (false);