Sibyx/phpGPX

<?php
/**
 * ElevationGainLossCalculator.php
 *
 * @author Jens Hassler
 * @since  07/2018
 */

namespace phpGPX\Helpers;

use phpGPX\Models\Point;
use phpGPX\phpGPX;

class ElevationGainLossCalculator
{
    /**
     * @param Point[]|array $points
     * @return array
     */
    public static function calculate(array $points)
    {
        $cumulativeElevationGain = 0;
        $cumulativeElevationLoss = 0;

        $pointCount = count($points);

        $lastConsideredElevation = 0;

        for ($p = 0; $p < $pointCount; $p++) {
            $curElevation = $points[$p]->elevation;

            // skip points with empty elevation
            if ($curElevation === null) {
                continue;
            }

            // skip points with 0 elevation if configuration allows
            if (phpGPX::$IGNORE_ELEVATION_0 && $curElevation == 0) {
                continue;
            }

            // skip the first point
            if ($p === 0) {
                $lastConsideredElevation = $curElevation;
                continue;
            }

            // calculate the delta from current point to last considered point
            $elevationDelta = $curElevation - $lastConsideredElevation;

            // if smoothing is applied we only consider points with a delta above the threshold (e.g. 2 meters)
            if (phpGPX::$APPLY_ELEVATION_SMOOTHING &&
                abs($elevationDelta) > phpGPX::$ELEVATION_SMOOTHING_THRESHOLD &&
                        (phpGPX::$ELEVATION_SMOOTHING_SPIKES_THRESHOLD === null || abs($elevationDelta) < phpGPX::$ELEVATION_SMOOTHING_SPIKES_THRESHOLD)) {
                $cumulativeElevationGain += ($elevationDelta > 0) ? $elevationDelta : 0;
                $cumulativeElevationLoss += ($elevationDelta < 0) ? abs($elevationDelta) : 0;

                $lastConsideredElevation = $curElevation;
            }

            // if smoothing is not applied we consider every point
            if (!phpGPX::$APPLY_ELEVATION_SMOOTHING) {
                $cumulativeElevationGain += ($elevationDelta > 0) ? $elevationDelta : 0;
                $cumulativeElevationLoss += ($elevationDelta < 0) ? abs($elevationDelta) : 0;

                $lastConsideredElevation = $curElevation;
            }
        }

        return [$cumulativeElevationGain, $cumulativeElevationLoss];
    }
}