diff --git a/libs/kaptan-drivers/src/mpu6000/mod.rs b/libs/kaptan-drivers/src/mpu6000/mod.rs
index a610301..eba47bf 100644
--- a/libs/kaptan-drivers/src/mpu6000/mod.rs
+++ b/libs/kaptan-drivers/src/mpu6000/mod.rs
@@ -5,7 +5,7 @@ mod error;
 mod registers;
 mod sample;
 
-use kaptan_sensor::ImuSnapshot;
+use kaptan_sensor::imu::ImuSnapshot;
 use kaptan_spi::{SpiCompletion, SpiDevice};
 use kaptan_time::Timestamp;
 
diff --git a/libs/kaptan-drivers/src/mpu6000/sample.rs b/libs/kaptan-drivers/src/mpu6000/sample.rs
index a793380..cadaf30 100644
--- a/libs/kaptan-drivers/src/mpu6000/sample.rs
+++ b/libs/kaptan-drivers/src/mpu6000/sample.rs
@@ -1,6 +1,6 @@
 //! MPU6000 burst-sample decoding.
 
-use kaptan_sensor::ImuSnapshot;
+use kaptan_sensor::imu::ImuSnapshot;
 use kaptan_time::Timestamp;
 
 use super::{config::Mpu6000Config, registers::SAMPLE_BYTES};
diff --git a/libs/kaptan-runtime/src/imu.rs b/libs/kaptan-runtime/src/imu.rs
index 0c5ff74..307ee28 100644
--- a/libs/kaptan-runtime/src/imu.rs
+++ b/libs/kaptan-runtime/src/imu.rs
@@ -1,7 +1,7 @@
 //! Single-owner MPU acquisition service.
 
 use kaptan_drivers::mpu6000::{Error as Mpu6000Error, Mpu6000, Mpu6000Event};
-use kaptan_sensor::ImuSnapshot;
+use kaptan_sensor::imu::ImuSnapshot;
 use kaptan_spi::{SpiCompletion, SpiDevice};
 use kaptan_time::MonotonicClock;
 
diff --git a/libs/kaptan-sensor/src/imu.rs b/libs/kaptan-sensor/src/imu.rs
new file mode 100644
index 0000000..c81fafb
--- /dev/null
+++ b/libs/kaptan-sensor/src/imu.rs
@@ -0,0 +1,37 @@
+//! Inertial measurement unit observations.
+
+use kaptan_time::Timestamp;
+
+/// Coherent IMU observation in the board body frame.
+///
+/// Acceleration is milligravity, angular rate is milliradians per second, and
+/// temperature is centidegrees Celsius. The board-frame transform is complete
+/// before this value is published.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct ImuSnapshot {
+    /// Monotonic timestamp captured at acquisition interrupt entry.
+    pub timestamp: Timestamp,
+    /// Body-frame acceleration in milligravity.
+    pub acceleration_milligravity: [i16; 3],
+    /// Body-frame angular rate in milliradians per second.
+    pub angular_rate_milliradians_per_second: [i16; 3],
+    /// Sensor temperature in centidegrees Celsius.
+    pub temperature_centidegrees_celsius: i16,
+}
+
+impl ImuSnapshot {
+    /// Creates one accepted IMU observation.
+    pub const fn new(
+        timestamp: Timestamp,
+        acceleration_milligravity: [i16; 3],
+        angular_rate_milliradians_per_second: [i16; 3],
+        temperature_centidegrees_celsius: i16,
+    ) -> Self {
+        Self {
+            timestamp,
+            acceleration_milligravity,
+            angular_rate_milliradians_per_second,
+            temperature_centidegrees_celsius,
+        }
+    }
+}
diff --git a/libs/kaptan-sensor/src/lib.rs b/libs/kaptan-sensor/src/lib.rs
index 9d6e878..d10ec66 100644
--- a/libs/kaptan-sensor/src/lib.rs
+++ b/libs/kaptan-sensor/src/lib.rs
@@ -6,38 +6,7 @@
 
 #![no_std]
 
-use kaptan_time::Timestamp;
-
-/// Coherent IMU observation in the board body frame.
-///
-/// Acceleration is milligravity, angular rate is milliradians per second, and
-/// temperature is centidegrees Celsius. The board-frame transform is complete
-/// before this value is published.
-#[derive(Clone, Copy, Debug, Eq, PartialEq)]
-pub struct ImuSnapshot {
-    /// Monotonic timestamp captured at acquisition interrupt entry.
-    pub timestamp: Timestamp,
-    /// Body-frame acceleration in milligravity.
-    pub acceleration_milligravity: [i16; 3],
-    /// Body-frame angular rate in milliradians per second.
-    pub angular_rate_milliradians_per_second: [i16; 3],
-    /// Sensor temperature in centidegrees Celsius.
-    pub temperature_centidegrees_celsius: i16,
-}
-
-impl ImuSnapshot {
-    /// Creates one accepted IMU observation.
-    pub const fn new(
-        timestamp: Timestamp,
-        acceleration_milligravity: [i16; 3],
-        angular_rate_milliradians_per_second: [i16; 3],
-        temperature_centidegrees_celsius: i16,
-    ) -> Self {
-        Self {
-            timestamp,
-            acceleration_milligravity,
-            angular_rate_milliradians_per_second,
-            temperature_centidegrees_celsius,
-        }
-    }
-}
+/// Inertial measurement unit observations.
+pub mod imu;
+/// Distance sensor observations.
+pub mod range;
diff --git a/libs/kaptan-sensor/src/range.rs b/libs/kaptan-sensor/src/range.rs
new file mode 100644
index 0000000..fca649e
--- /dev/null
+++ b/libs/kaptan-sensor/src/range.rs
@@ -0,0 +1,26 @@
+//! Distance sensor observations.
+
+use kaptan_time::Timestamp;
+
+/// Coherent range observation in the sensor frame.
+///
+/// The timestamp is captured when the measurement is requested. Distance is
+/// expressed in millimetres so rangefinders with centimetre resolution can be
+/// published without floating-point conversion.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct RangeSnapshot {
+    /// Monotonic timestamp captured when the acquisition was requested.
+    pub timestamp: Timestamp,
+    /// Measured distance in millimetres.
+    pub distance_millimetres: u32,
+}
+
+impl RangeSnapshot {
+    /// Creates one accepted range observation.
+    pub const fn new(timestamp: Timestamp, distance_millimetres: u32) -> Self {
+        Self {
+            timestamp,
+            distance_millimetres,
+        }
+    }
+}