From 08390be391c38054d874ffb44cb7e64c64136201 Mon Sep 17 00:00:00 2001
From: Julian Smith <jules@op59.net>
Date: Fri, 25 Jun 2021 16:51:40 +0100
Subject: [PATCH] src/AIModel/: use Simgear's unit conversion constants, e.g.
 SG_KT_TO_FPS.

---
 src/AIModel/AIMultiplayer.cxx |  7 ++-----
 src/AIModel/AIShip.cxx        | 11 +++--------
 2 files changed, 5 insertions(+), 13 deletions(-)

diff --git a/src/AIModel/AIMultiplayer.cxx b/src/AIModel/AIMultiplayer.cxx
index a8d13286a..3995a6859 100644
--- a/src/AIModel/AIMultiplayer.cxx
+++ b/src/AIModel/AIMultiplayer.cxx
@@ -713,14 +713,11 @@ void FGAIMultiplayer::update(double dt)
     _vBodyNode->setValue(ecLinearVel[1] * SG_METER_TO_FEET);
     _wBodyNode->setValue(ecLinearVel[2] * SG_METER_TO_FEET);
     
-    double knots2si = 1852.0/3600;      // Knots to metres/sec.
-    double ft2si = 12 * 2.54 / 100;     // Feet to metres
-    
     if (ecLinearVel[0] == 0) {
         // MP packets for carriers have zero ecLinearVel, but do specify
         // velocities/speed-kts.
         double speed_kts = props->getDoubleValue("velocities/speed-kts");
-        double speed_fps = speed_kts * knots2si / ft2si;
+        double speed_fps = speed_kts * SG_KT_TO_FPS;
         _uBodyNode->setDoubleValue(speed_fps);
     }
     
@@ -767,7 +764,7 @@ void FGAIMultiplayer::update(double dt)
         // doesn't slip when carrier changes course. Also would be good to
         // handle vbody and wbody?]
         //
-        m_node_ai_latch_speed_kts->setDoubleValue(_uBodyNode->getDoubleValue() * ft2si / knots2si);
+        m_node_ai_latch_speed_kts->setDoubleValue(_uBodyNode->getDoubleValue() * SG_FPS_TO_KT);
     }
     assert(m_node_ai_latch == props->getNode("ai-latch"));
 
diff --git a/src/AIModel/AIShip.cxx b/src/AIModel/AIShip.cxx
index 9cc805219..d7b4d837c 100644
--- a/src/AIModel/AIShip.cxx
+++ b/src/AIModel/AIShip.cxx
@@ -240,16 +240,13 @@ void FGAIShip::update(double dt) {
 
         // Compute the velocity in m/s in the body frame
         // <speed> is in knots.
-        double knots2si = 1852.0/3600;
-        aip.setBodyLinearVelocity(SGVec3d(speed * knots2si, 0, 0));
+        aip.setBodyLinearVelocity(SGVec3d(speed * SG_KT_TO_MPS, 0, 0));
 
         // Update speed_fps so that velocities/uBody-fps will be set. <speed>
         // is in knots.
         //
         {
-            double knots2si = 1852.0/3600;      // Knots to metres/sec.
-            double ft2si = 12 * 2.54 / 100;     // Feet to metres
-            speed_fps = speed * knots2si / ft2si;
+            speed_fps = speed * SG_KT_TO_FPS;
         }
         FGAIBase::update(dt);
         Run(dt);
@@ -331,9 +328,7 @@ void FGAIShip::Run(double dt) {
         z-back. */
         SGQuatd q(-0.5, -0.5, 0.5, 0.5);
         
-        double knots2si = 1852.0/3600;
-        
-        SGVec3d offset(0, 0, -speed * knots2si * dt);
+        SGVec3d offset(0, 0, -speed * SG_KT_TO_MPS * dt);
         position += (ec2body * q).backTransform(offset);
         pos = SGGeod::fromCart(position);