Attempt to smooth out the velocity readings

If the velocity is slower than FAST then we look back up to 30 seconds and
calculate the velocity for the past 30 seconds instead.

For the first version I'm not doing the average of the changes but simply
the change from beginning to end.

The alternative would be to do another triangle smoothing or something
like that - but as we don't know how many samples we have in the 30 second
window, it's a little harder here.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

diff --git a/profile.c b/profile.c
index 270b203c4d365e7da7429104e575805f686c378e..9a9d98642934bc308e12b0f0a9be7b5cb6497d0e 100644 (file)
--- a/profile.c
+++ b/profile.c
@@ -10,6 +10,7 @@
 
 int selected_dive = 0;
 
+typedef enum { STABLE, SLOW, MODERATE, FAST, CRAZY } velocity_t;
 /* Plot info with smoothing, velocity indication
  * and one-, two- and three-minute minimums and maximums */
 struct plot_info {
@@ -24,7 +25,7 @@ struct plot_info {
                /* Depth info */
                int val;
                int smoothed;
-               enum { STABLE, SLOW, MODERATE, FAST, CRAZY } velocity;
+               velocity_t velocity;
                struct plot_data *min[3];
                struct plot_data *max[3];
                int avg[3];
@@ -547,6 +548,33 @@ static void analyze_plot_info_minmax(struct plot_data *entry, struct plot_data *
        analyze_plot_info_minmax_minute(entry, first, last, 2);
 }
 
+static velocity_t velocity(int speed)
+{
+       velocity_t v;
+
+       if (speed < -304) /* ascent faster than -60ft/min */
+               v = CRAZY;
+       else if (speed < -152) /* above -30ft/min */
+               v = FAST;
+       else if (speed < -76) /* -15ft/min */
+               v = MODERATE;
+       else if (speed < -25) /* -5ft/min */
+               v = SLOW;
+       else if (speed < 25) /* very hard to find data, but it appears that the recommendations
+                               for descent are usually about 2x ascent rate; still, we want 
+                               stable to mean stable */
+               v = STABLE;
+       else if (speed < 152) /* between 5 and 30ft/min is considered slow */
+               v = SLOW;
+       else if (speed < 304) /* up to 60ft/min is moderate */
+               v = MODERATE;
+       else if (speed < 507) /* up to 100ft/min is fast */
+               v = FAST;
+       else /* more than that is just crazy - you'll blow your ears out */
+               v = CRAZY;
+
+       return v;
+}
 static struct plot_info *analyze_plot_info(struct plot_info *pi)
 {
        int i;
@@ -583,28 +611,17 @@ static struct plot_info *analyze_plot_info(struct plot_info *pi)
                        entry->smoothed = (val+4) / 9;
                }
                /* vertical velocity in mm/sec */
+               /* Linus wants to smooth this - let's at least look at the samples that aren't FAST or CRAZY */
                if (entry[0].sec - entry[-1].sec) {
-                       val = (entry[0].val - entry[-1].val) / (entry[0].sec - entry[-1].sec);
-                       if (val < -304) /* ascent faster than -60ft/min */
-                               entry->velocity = CRAZY;
-                       else if (val < -152) /* above -30ft/min */
-                               entry->velocity = FAST;
-                       else if (val < -76) /* -15ft/min */
-                               entry->velocity = MODERATE;
-                       else if (val < -25) /* -5ft/min */
-                               entry->velocity = SLOW;
-                       else if (val < 25) /* very hard to find data, but it appears that the recommendations
-                                             for descent are usually about 2x ascent rate; still, we want 
-                                             stable to mean stable */
-                               entry->velocity = STABLE;
-                       else if (val < 152) /* between 5 and 30ft/min is considered slow */
-                               entry->velocity = SLOW;
-                       else if (val < 304) /* up to 60ft/min is moderate */
-                               entry->velocity = MODERATE;
-                       else if (val < 507) /* up to 100ft/min is fast */
-                               entry->velocity = FAST;
-                       else /* more than that is just crazy - you'll blow your ears out */
-                               entry->velocity = CRAZY;
+                       entry->velocity = velocity((entry[0].val - entry[-1].val) / (entry[0].sec - entry[-1].sec));
+                        /* if our samples are short and we aren't too FAST*/
+                       if (entry[0].sec - entry[-1].sec < 30 && entry->velocity < FAST) { 
+                               int past = -2;
+                               while (pi->entry <= entry-past && entry[0].sec - entry[past].sec < 30)
+                                       past--;
+                               entry->velocity = velocity((entry[0].val - entry[past].val) / 
+                                                       (entry[0].sec - entry[past].sec));
+                       }
                } else
                        entry->velocity = STABLE;
        }