NASA weight filter

The purpose of this filter is to eliminate weight changes caused by the beekeeper so the data only reflects weight changes made by the bees.

This weight filter works by calculating the change in weight (delta weight) between consecutive readings. The delta weight is divided by the time between the readings. If the weight change exceeds a threshold per unit time, it is assumed the bees could not change the weight of the hive that quickly and the weight change must be a manipulation change (a super, feeder, feed, etc. was added or removed) and it is not counted.

In the spring and summer this understates the weight of the hive. In the fall and winter, it can overstate the weight of the hive.

    if ( $last_weight ) {                                       # then have looped at least once and can calculate deltas
        $delta_weight = $weight - $last_weight;
        $delta_time = ($time - $last_time)/3600;
        $delta_rain =  $rain - $last_wx_rain;
        
        if ($delta_time) { $dwdt = $delta_weight/$delta_time; } # don't divide by zero (if two records have the same time)
        
                                                                # Begin NASA manipulation change filter
        if ( ($weight_filter eq "NASA") 
          && (abs $dwdt > $max_dwdt_lbs_per_hour)               # if the change in weight exceeds the threshold
          && ($start_zero_weight == 0)                          # and the data is not starting off with zeros
          && ($quality != 6) )                                  # and this record is not flagged as a swarm (Quality 6)
           {                                                    # then don't count the change as daily change,
           $manipulation_change +=  $delta_weight;              # count it as manipulation change
           }
        else
           {
           $daily_change += $delta_weight;                      # otherwise, count it as part of the daily change
           }
        }
        else {                                                  #first time through
             $daily_change = $weight;
             $first_graph_date = $row[0];
             $last_wx_rain = $row[10];
             $delta_rain = 0;
        }
        $last_weight = $weight;
        $weight = $daily_change; 
                                                                 # end NASA filter
        $last_temperature = $temperature;
        $last_time = $time;