+/* calculate OTU for a dive */
+static double calculate_otu(struct dive *dive)
+{
+ int i;
+ double otu = 0.0;
+
+ for (i = 1; i < dive->samples; i++) {
+ int t;
+ double po2;
+ struct sample *sample = dive->sample + i;
+ struct sample *psample = sample - 1;
+ t = sample->time.seconds - psample->time.seconds;
+ po2 = dive->cylinder[sample->cylinderindex].gasmix.o2.permille / 1000.0 *
+ (sample->depth.mm + 10000) / 10000.0;
+ if (po2 >= 0.5)
+ otu += pow(po2 - 0.5, 0.83) * t / 30.0;
+ }
+ return otu;
+}