Automatic merge of T1.6-108-g8fb3285d6 and 13 pull requests

- Pull request #1156 at f46d5f2: Fix incorrectly disabled options in train operations window
- Pull request #1091 at 492795a: Automatic speed control
- Pull request #1120 at ba3c47f: Automatically Calculate Friction Values if Missing
- Pull request #1121 at 91d2d26: Manually Override Articulation
- Pull request #1124 at e241a0d: Built-in PBL2 brake controller
- Pull request #1157 at 39cd994: Dynamic brake authorization by TCS
- Pull request #1159 at 48c9a63: Skip OR warnings about TSRE-specific token Ruler
- Pull request #1162 at 2516cce: specifies precedence of DDS over ACE
- Pull request #1163 at 2f9e292: Fix: Crash when using Camera 8 and F9.
- Pull request #1164 at 1ad9889: Fix: F9 crashes with a front coupled single steam locomotive by Csantucci.
- Pull request #1082 at 625c917: Allow variable water level in glass gauge
- Pull request #1128 at 086d502: Particle Emitter Overhaul
- Pull request #1160 at 9dc6b3b: Route Based TTrack Sounds

Author: openrails-bot

Source/Orts.Simulation/Simulation/RollingStocks/MSTSSteamLocomotive.cs

@@ -1495,7 +1495,6 @@ public override void Initialize()
                     Trace.TraceWarning("Boiler Volume not found in ENG file, or doesn't appear to be a valid figure, and has been set to {0} Ft^3", BoilerVolumeFT3);
             }
 
-
             // Set up boiler water defaults
 
             // Water Gauge Length - always use OR entered value as first preference
@@ -7065,13 +7064,12 @@ private void UpdateWaterGauge()
             WaterGlassLevelIN = waterGlassFractionLevel * Me.ToIn(WaterGlassLengthM);
             WaterGlassLevelIN = MathHelper.Clamp(WaterGlassLevelIN, 0, Me.ToIn(WaterGlassLengthM));
 
-
             // Calculate water glass level when on gradient
 
             var boilerangleRad = Math.Atan(CurrentElevationPercent / 100);
 
-            // water variation is calculated as the side of a triangle with half the boiler length as the hypotenuse
-            var waterVariationLevelM = (float)Math.Sin(boilerangleRad) * BoilerLengthM / 2.0f;
+            // water variation is calculated as the opposite side of a triangle with half the boiler length as the reference length (Adjacent side)
+            var waterVariationLevelM = (float)Math.Tan(boilerangleRad) * (BoilerLengthM / 2.0f);
 
             float glassLevelGradientM = 0;