# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1381767681 0
# Node ID ca7f7e9b8be5e34706695c22cb4ba90ed3bee3e5
# Parent  76d46d9d2322ba7b7b4097c25d2470dfdb58b391
Switched to using the dynamic field vector and the static y axis to produce the
magnetic north vector, although it is unreliable, probably because of "soft iron
distortion".

diff -r 76d46d9d2322 -r ca7f7e9b8be5 main.c
--- a/main.c	Mon Oct 14 16:17:00 2013 +0000
+++ b/main.c	Mon Oct 14 16:21:21 2013 +0000
@@ -37,7 +37,7 @@
 
     vectorf _viewx, _viewy, _viewz,
             _accelerationD, _accelerationRD,
-            _fieldD;
+            _fieldD, _fieldN;
 
     /* Timekeeping. */
 
@@ -190,6 +190,8 @@
                 flush();
             }
 
+            /* Additional textual output. */
+
             printf("Period? %d\n", imu_period);
             printf("Direction? %.4f\n", raddeg(direction));
             printf("Elevation? %.4f (%.4f)\n", raddeg(elevation), raddeg(elevationA));
@@ -210,6 +212,7 @@
             _accelerationD = accelerationD;
             _accelerationRD = accelerationRD;
             _fieldD = fieldD;
+            _fieldN = fieldN;
             pthread_mutex_unlock(&mutex);
 
             clear();
@@ -226,6 +229,11 @@
             _fieldD.z *= 10;
             gui_point(&_viewx, &_viewy, &_viewz, &_fieldD, 0, 0, 255, 127);
 
+            _fieldN.x *= 10;
+            _fieldN.y *= 10;
+            _fieldN.z *= 10;
+            gui_point(&_viewx, &_viewy, &_viewz, &_fieldN, 255, 0, 0, 127);
+
             flush();
 
             gui_updated = now;
diff -r 76d46d9d2322 -r ca7f7e9b8be5 measure.c
--- a/measure.c	Mon Oct 14 16:17:00 2013 +0000
+++ b/measure.c	Mon Oct 14 16:21:21 2013 +0000
@@ -233,11 +233,11 @@
                 directionF0 = vectorf_direction(&field0);
                 elevationF0 = vectorf_elevation(&field0);
 
-                /* Determine the east and north vectors using static field information. */
+                /* Determine the east and north vectors using dynamic field information. */
 
-                vectorf_cross(&accelerationRD, &fieldD0, &fieldE);
+                vectorf_cross(&viewy0, &fieldD, &fieldE);
                 vectorf_normalise(&fieldE, &fieldE);
-                vectorf_cross(&fieldE, &accelerationRD, &fieldN);
+                vectorf_cross(&fieldE, &viewy0, &fieldN);
             }
 
             /* Subtract the constant background acceleration. */