Added simplified temperature correction as a cross-check and unit tests

Author: fvalka

src/lib/calculations/temperature-correction/esdu-temperature-correction.svelte

@@ -55,7 +55,6 @@
       }
 
       console.debug("Resulting correction to be added to the elevation: hPAirplane %s", hPAirplane);
-
       return add(aerodrome_elevation, hPAirplane);
     }
 

src/lib/calculations/temperature-correction/simplified-temperature-correction.svelte

@@ -0,0 +1,30 @@
+<script context="module" lang="ts">
+    import { add, parse, subtract, unit, type Unit } from "mathjs";
+
+    const isa_temperature_lapse_rate = unit("0.00198 K/ft");
+
+    const equation_t0 = parse("tAerodrome + L0 * HAerodrome");
+    const equation_height_correction = parse("H * ((15K - t0)/(273K + t0 - 0.5 * L0 * (H + HSS)))");
+
+    export function simplifiedAltitudeCorrection (input_altitude: Unit, aerodrome_elevation: Unit, aerodrome_ground_temperature: Unit) {
+        let input_height = subtract(input_altitude, aerodrome_elevation);
+
+        const calculation_parameters_t0 = {
+            tAerodrome: aerodrome_ground_temperature,
+            HAerodrome: aerodrome_elevation,
+            L0: isa_temperature_lapse_rate
+        };
+        const t0 = equation_t0.evaluate(calculation_parameters_t0);
+
+        const calculation_parameters_height_correction = {
+            H: input_height, 
+            t0: t0,
+            L0: isa_temperature_lapse_rate,
+            HSS: aerodrome_elevation,
+        };
+
+        const height_correction = equation_height_correction.evaluate(calculation_parameters_height_correction);
+
+        return add(input_altitude, height_correction);
+    }
+</script>

src/lib/components/AerodromeInput.svelte

@@ -44,6 +44,11 @@
         if (calculatedIsaDeviation > 0) {
             inputErrors.push("Calculations are only possible for ISA deviations smaller than 0. So temperatures colder than the standard atmosphere.");
         }
+        
+        // Normal errors, all will be shown at once
+        if (calculatedIsaDeviation <- 80) {
+            inputErrors.push("Calculations are only possible for ISA deviations down to -80 °C");
+        }
 
         if (aerodrome_elevation_ft > 36000) {
             inputErrors.push("The temperature correction calculation is only valid up to 36000 ft please enter a smaller input value!");