Update State::getState() to handle the case of one state (like a framing camera.) (#364)

* Update format of range conversion coefficients isd output to include a separate list for times. Also update driver, test data, and remove unneeded semicolons

* Fix documentaion error

* fix other documentation error

* Added the case of 1 state (1 position, time, and maybe velocity) to getState()

* Roll back ale version # and accidental json submodule deletion

include/ale/InterpUtils.h

@@ -75,7 +75,7 @@ namespace ale {
                                      double time, int order=8);
 
    /**
-    *@brief Interpolates the spacecrafts position along a path generated from a set of points,
+    *@brief Interpolates the spacecraft's position along a path generated from a set of points,
               times, and a time of observation
     *@param points A double vector of points
     *@param times A double vector of times

src/States.cpp

@@ -111,6 +111,7 @@ namespace ale {
 
 
   State States::getState(double time, PositionInterpolation interp) const {
+    if (m_ephemTimes.size() > 1) {
       int lowerBound = interpolationIndex(m_ephemTimes, time); 
       // try to copy the surrounding 8 points as that's the most possibly needed
       int interpStart = std::max(0, lowerBound - 3);
@@ -160,6 +161,17 @@ namespace ale {
       }
       return State(position, velocity);
     }
+    else if (hasVelocity()) {
+      // Here we have: 1 state (1 time, 1 position, 1 velocity)
+      // x_f = x_i + v * (t_f - t-i)
+      Vec3d position = m_states[0].position + m_states[0].velocity*(time - m_ephemTimes[0]);
+      Vec3d velocity = m_states[0].velocity;
+      return State(position, velocity);
+    }
+    else { // Here we have: only 1 time and 1 state, so just return the only state.
+      return State(m_states[0]);
+    }
+  }
 
 
   Vec3d States::getPosition(double time, PositionInterpolation interp) const {

tests/ctests/StatesTests.cpp

@@ -313,6 +313,40 @@ TEST(StatesTest, minimizeCache_false) {
 }
 
 
+TEST(StatesTest, OneStateNoVelocity) {
+  std::vector<double> ephemTimes = {0.0};
+  std::vector<Vec3d> positions = {Vec3d(2.0, 3.0, 4.0)};
+
+  States testState(ephemTimes, positions);
+  State result = testState.getState(1.0);
+  EXPECT_NEAR(result.position.x, 2.0, 1e-5);
+  EXPECT_NEAR(result.position.y, 3.0, 1e-4);
+  EXPECT_NEAR(result.position.z, 4.0, 1e-5);
+}
+
+TEST(StatesTest, OneStateWithVelocity) {
+  std::vector<double> ephemTimes = {1.0};
+  std::vector<Vec3d> positions = {Vec3d(2.0, 3.0, 4.0)};
+  std::vector<Vec3d> velocities = {Vec3d(5.0, 6.0, -1.0)};
+
+  States testState(ephemTimes, positions, velocities);
+  State result = testState.getState(2.0);
+  EXPECT_NEAR(result.position.x, 7.0, 1e-5);
+  EXPECT_NEAR(result.position.y, 9.0, 1e-4);
+  EXPECT_NEAR(result.position.z, 3.0, 1e-5);
+  EXPECT_NEAR(result.velocity.x, 5.0, 1e-6);
+  EXPECT_NEAR(result.velocity.y, 6.0, 1e-6);
+  EXPECT_NEAR(result.velocity.z, -1.0, 1e-6);
+
+  result = testState.getState(-1.0);
+  EXPECT_NEAR(result.position.x, -8.0, 1e-5);
+  EXPECT_NEAR(result.position.y, -9.0, 1e-4);
+  EXPECT_NEAR(result.position.z, 6.0, 1e-5);
+  EXPECT_NEAR(result.velocity.x, 5.0, 1e-6);
+  EXPECT_NEAR(result.velocity.y, 6.0, 1e-6);
+  EXPECT_NEAR(result.velocity.z, -1.0, 1e-6);
+}
+
 // This test checks to see if the minimized cache looks identical to ISIS's minimized cache for
 // a Dawn IR image VIR_IR_1A_1_362681634_1 (located in dawnvir2isis's IR app test.)
 // Values were obtained by adding strategic couts to SpicePosition.cpp, running spiceinit, and