Android Open Source - geoar-app Adaptive Low Pass Sensor Buffer

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License

The source code is released under:

Apache License

Java Source Code

/**
 * Copyright 2012 52North Initiative for Geospatial Open Source Software GmbH
 *//ww w.ja va2  s  .c  om
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.n52.geoar.tracking.location;


/**
 * 
 * Adaptive low pass filter for sensor data, adjusts alpha value based on
 * distance to previous values
 * 
 * @author Holger Hopmann
 * 
 */
public class AdaptiveLowPassSensorBuffer extends SensorBuffer {
  private float[] buffer;
  private float alphaLow;
  private float alphaHigh;
  private float thresholdLow;
  private float thresholdHigh;

  public AdaptiveLowPassSensorBuffer(int dataLength, float thresholdLow,
      float thresholdHigh, float alphaLow, float alphaHigh) {
    super(dataLength);
    this.alphaLow = alphaLow;
    this.alphaHigh = alphaHigh;
    this.thresholdLow = thresholdLow;
    this.thresholdHigh = thresholdHigh;
    buffer = new float[dataLength];
  }

  private boolean hasValues;

  public void put(float[] sensordata) {

    float dist = 0;
    for (int i = 0; i < dataLength; i++) {
      dist += Math.abs(buffer[i] - sensordata[i]);
    }
    dist /= (float) dataLength;

    float alpha;
    if (dist < thresholdLow) {
      alpha = alphaLow;
    } else if (dist > thresholdHigh) {
      alpha = alphaHigh;
    } else {
      float thresholdDiff = thresholdHigh - thresholdLow;
      float alphaDiff = alphaHigh - alphaLow;

      alpha = alphaLow + alphaDiff
          * ((thresholdHigh - dist) / thresholdDiff);
    }

    for (int i = 0; i < dataLength; i++) {
      buffer[i] = alpha * sensordata[i] + (1 - alpha) * buffer[i];
    }
    hasValues = true;
  }

  public float[] get() {
    return buffer;
  }

  public boolean hasValues() {
    return hasValues;
  }
}

Java Source Code List

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