diff --git a/gtsam/navigation/ScenarioRunner.cpp b/gtsam/navigation/ScenarioRunner.cpp
index 6e713598f..d1cf71eb9 100644
--- a/gtsam/navigation/ScenarioRunner.cpp
+++ b/gtsam/navigation/ScenarioRunner.cpp
@@ -40,10 +40,9 @@ ImuFactor::PreintegratedMeasurements ScenarioRunner::integrate(
   const size_t nrSteps = T / dt;
   double t = 0;
   for (size_t k = 0; k < nrSteps; k++, t += dt) {
-    Rot3 bRn = scenario_->rotation(t).transpose();
-    Vector3 measuredOmega = scenario_->omega_b(t);
+    Vector3 measuredOmega = measured_angular_velocity(t);
     if (gyroSampler) measuredOmega += gyroSampler->sample() / sqrt_dt;
-    Vector3 measuredAcc = scenario_->acceleration_b(t) - bRn * gravity_n();
+    Vector3 measuredAcc = measured_acceleration(t);
     if (accSampler) measuredAcc += accSampler->sample() / sqrt_dt;
     pim.integrateMeasurement(measuredAcc, measuredOmega, dt);
   }
diff --git a/gtsam/navigation/ScenarioRunner.h b/gtsam/navigation/ScenarioRunner.h
index 0c8545061..1cb717292 100644
--- a/gtsam/navigation/ScenarioRunner.h
+++ b/gtsam/navigation/ScenarioRunner.h
@@ -23,7 +23,10 @@ namespace gtsam {
 
 class Sampler;
 
-/// Simple class to test navigation scenarios
+/*
+ *  Simple class to test navigation scenarios.
+ *  Takes a trajectory scenario as input, and can generate IMU measurements
+ */
 class ScenarioRunner {
  public:
   ScenarioRunner(const Scenario* scenario, double imuSampleTime = 1.0 / 100.0,
@@ -33,11 +36,22 @@ class ScenarioRunner {
         gyroNoiseModel_(noiseModel::Isotropic::Sigma(3, gyroSigma)),
         accNoiseModel_(noiseModel::Isotropic::Sigma(3, accSigma)) {}
 
-  const double& imuSampleTime() const { return imuSampleTime_; }
-
   // NOTE(frank): hardcoded for now with Z up (gravity points in negative Z)
   // also, uses g=10 for easy debugging
-  Vector3 gravity_n() const { return Vector3(0, 0, -10.0); }
+  static Vector3 gravity_n() { return Vector3(0, 0, -10.0); }
+
+  // A gyro simly measures angular velocity in body frame
+  Vector3 measured_angular_velocity(double t) const {
+    return scenario_->omega_b(t);
+  }
+
+  // An accelerometer measures acceleration in body, but not gravity
+  Vector3 measured_acceleration(double t) const {
+    Rot3 bRn = scenario_->rotation(t).transpose();
+    return scenario_->acceleration_b(t) - bRn * gravity_n();
+  }
+
+  const double& imuSampleTime() const { return imuSampleTime_; }
 
   const noiseModel::Diagonal::shared_ptr& gyroNoiseModel() const {
     return gyroNoiseModel_;
@@ -70,7 +84,7 @@ class ScenarioRunner {
   }
 
   /// Compute a Monte Carlo estimate of the PIM pose covariance using N samples
-  Matrix6 estimatePoseCovariance(double T, size_t N = 100) const;
+  Matrix6 estimatePoseCovariance(double T, size_t N = 1000) const;
 
  private:
   const Scenario* scenario_;