Add proj frame offset to groundtruth

Signed-off-by: Thomas Sedlmayer <tsedlmayer@pmsfit.de>

Author: thomassedlmayer

osi_groundtruth.proto

@@ -133,7 +133,8 @@ message GroundTruth
     optional uint32 country_code = 13;
 
     // Projection string that allows to transform all coordinates in GroundTruth
-    // into a different cartographic projection.
+    // into a different cartographic projection after the \c proj_frame_offset
+    // has been applied.
     //
     // The string follows the PROJ rules for projections [1].
     //
@@ -178,4 +179,45 @@ message GroundTruth
     // Logical lanes used e.g. by traffic agents
     //
     repeated LogicalLane logical_lane = 19;
+
+    // Coordinate frame offset to be used for PROJ transformations.
+    //
+    optional ProjFrameOffset proj_frame_offset = 20;
+
+    //
+    // \brief Coordinate frame offset to transform from OSI's global coordinate
+    // system to a coordinate reference system to be used for given PROJ
+    // transformations.
+    //
+    // If an offset is defined, always apply the \c proj_frame_offset on
+    // global OSI coordinates before applying any transformations defined in
+    // \c proj_string.
+    //
+    // To apply the offset, global coordinates are first translated by the given
+    // positional offset (x,y,z). Then, the yaw angle is used to rotate around
+    // the new origin.
+    //
+    // The offset is applied on global OSI coordinates using an affine
+    // transformation with rotation around z-axis:
+    // xWorld = xOSI * cos(yaw) - yOSI * sin(yaw) + xOffset
+    // yWorld = xOSI * sin(yaw) + yOSI * cos(yaw) + yOffset
+    // zWorld = zOSI + zOffset
+    //
+    // If no yaw is provided (recommended), the formulas simplify to:
+    // xWorld = xOSI + xOffset
+    // yWorld = yOSI + yOffset
+    // zWorld = zOSI + zOffset
+    //
+    message ProjFrameOffset
+    {
+        // Positional offset for relocation of the coordinate frame.
+        //
+        optional Vector3d position = 1;
+
+        // Yaw/heading angle for re-orientation of the coordinate frame around
+        // the z-axis.
+        //
+        optional double yaw = 2;
+    }
+
 }