altoslib: Use feet per second for imperial speed

This is more useful during descent than miles per hour...

Signed-off-by: Keith Packard <keithp@keithp.com>

2 files changed, 13 insertions, 5 deletions

diff --git a/altoslib/AltosConvert.java b/altoslib/AltosConvert.java
index 25bbf7a0..265b5f0f 100644
--- a/altoslib/AltosConvert.java
+++ b/altoslib/AltosConvert.java
@@ -325,6 +325,14 @@ public class AltosConvert {
 		return miles_to_meters(mps) / 3600;
  	}
 
+	public static double mps_to_fps(double mps) {
+		return meters_to_miles(mps) * 5280;
+ 	}
+
+	public static double fps_to_mps(double mps) {
+		return miles_to_meters(mps) / 5280;
+ 	}
+
 	public static double meters_to_mach(double meters) {
 		return meters / 343;		/* something close to mach at usual rocket sites */
 	}
diff --git a/altoslib/AltosSpeed.java b/altoslib/AltosSpeed.java
index fb1c5e3f..e09bbb7a 100644
--- a/altoslib/AltosSpeed.java
+++ b/altoslib/AltosSpeed.java
@@ -21,29 +21,29 @@ public class AltosSpeed extends AltosUnits {
 
 	public double value(double v, boolean imperial_units) {
 		if (imperial_units)
-			return AltosConvert.meters_to_mph(v);
+			return AltosConvert.mps_to_fps(v);
 		return v;
 	}
 
 	public double inverse(double v, boolean imperial_units) {
 		if (imperial_units)
-			return AltosConvert.mph_to_meters(v);
+			return AltosConvert.fps_to_mps(v);
 		return v;
 	}
 
 	public String show_units(boolean imperial_units) {
 		if (imperial_units)
-			return "mph";
+			return "fps";
 		return "m/s";
 	}
 
 	public String say_units(boolean imperial_units) {
 		if (imperial_units)
-			return "miles per hour";
+			return "feet per second";
 		return "meters per second";
 	}
 
 	public int show_fraction(int width, boolean imperial_units) {
 		return width / 9;
 	}
-}
\ No newline at end of file
+}