new gpr

data_acq_and_processing/processing/locator/include/locator/observation.hpp

@@ -4,11 +4,11 @@ namespace radar::locator {
 
 // One outbound locator observation: object position relative to the radar in metres.
 // `crs` is the cross-range (X) coordinate; `dst` is the range (Z) coordinate.
-// Values are kept as float because they are quantised to two decimal places before
-// being serialised on the wire.
+// Values use double so that, after quantisation to one decimal place (decimetres),
+// they serialise to clean JSON (e.g. "12.3" rather than a float's "12.300000190734863").
 struct Observation {
-    float crs = 0.0F;
-    float dst = 0.0F;
+    double crs = 0.0;
+    double dst = 0.0;
 };
 
 }  // namespace radar::locator

data_acq_and_processing/processing/locator/src/payload_builder.cpp

@@ -42,10 +42,11 @@ constexpr std::uint32_t kMinTableColumns = 3U;  // [x_m, z_m, score, ...]
     return fallback;
 }
 
-// Quantise to two decimal places. Equivalent to Python's `round(value, 2)`
-// but explicit so behaviour does not silently depend on the local C library.
-[[nodiscard]] auto quantise_to_centimetres(float value) -> float {
-    return std::round(value * 100.0F) / 100.0F;
+// Quantise to one decimal place (0.1 m = decimetres). Equivalent to Python's
+// `round(value, 1)` but explicit so behaviour does not silently depend on the
+// local C library.
+[[nodiscard]] auto quantise_to_decimetres(double value) -> double {
+    return std::round(value * 10.0) / 10.0;
 }
 
 [[nodiscard]] auto passes_basic_filter(
@@ -156,8 +157,8 @@ auto observations_from_collection(
         quantised.reserve(visible.size());
         for (const auto& observation : visible) {
             quantised.push_back({
-                .crs = quantise_to_centimetres(observation.crs),
-                .dst = quantise_to_centimetres(observation.dst),
+                .crs = quantise_to_decimetres(observation.crs),
+                .dst = quantise_to_decimetres(observation.dst),
             });
         }
         return quantised;
@@ -172,8 +173,8 @@ auto observations_from_collection(
     result.reserve(kept);
     for (std::size_t index = 0; index < kept; ++index) {
         result.push_back({
-            .crs = quantise_to_centimetres(visible[index].crs),
-            .dst = quantise_to_centimetres(visible[index].dst),
+            .crs = quantise_to_decimetres(visible[index].crs),
+            .dst = quantise_to_decimetres(visible[index].dst),
         });
     }
     return result;