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Fix #65 - Show C/N0 instead of SNR on Android 7.0 and up
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@barbeau
barbeau committed Oct 20, 2016
1 parent ed81932 commit 6759784
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Showing 4 changed files with 93 additions and 132 deletions.
130 changes: 60 additions & 70 deletions GPSTest/src/main/java/com/android/gpstest/GpsSkyFragment.java
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,6 @@
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.location.GnssMeasurement;
import android.location.GnssMeasurementsEvent;
import android.location.GnssStatus;
import android.location.GpsSatellite;
Expand All @@ -43,8 +42,6 @@
import android.view.ViewTreeObserver;
import android.view.WindowManager;

import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;

public class GpsSkyFragment extends Fragment implements GpsTestActivity.GpsTestListener {
Expand Down Expand Up @@ -176,17 +173,16 @@ private static class GpsSkyView extends View implements GpsTestActivity.GpsTestL

private final int mSnrColors[];

private final float mCn0Thresholds[];

private final int mCn0Colors[];

private boolean mUseSnr = false;

Context mContext;

WindowManager mWindowManager;

/**
* Key is combination of sat ID and constellation type (GpsTestUtil.createGnssSatelliteKey()),
* and value is the SNR for that satellite. Needed to match GnssMeasurement events up with
* GnssStatus events.
*/
HashMap<String, Double> mSnrsForSats;

private Paint mHorizonActiveFillPaint, mHorizonInactiveFillPaint, mHorizonStrokePaint,
mGridStrokePaint,
mSatelliteFillPaint, mSatelliteStrokePaint, mNorthPaint, mNorthFillPaint,
Expand All @@ -196,7 +192,7 @@ private static class GpsSkyView extends View implements GpsTestActivity.GpsTestL

private boolean mStarted;

private float mSnrs[], mElevs[], mAzims[];
private float mSnrCn0s[], mElevs[], mAzims[]; // Holds either SNR or C/N0 - see #65

private int mPrns[], mConstellationType[];

Expand Down Expand Up @@ -244,6 +240,9 @@ public GpsSkyView(Context context) {
mSnrThresholds = new float[]{0.0f, 10.0f, 20.0f, 30.0f};
mSnrColors = new int[]{Color.GRAY, Color.RED, Color.YELLOW, Color.GREEN};

mCn0Thresholds = new float[]{0.0f, 16.6f, 33.3f, 50.0f};
mCn0Colors = new int[]{Color.GRAY, Color.RED, Color.YELLOW, Color.GREEN};

mNorthPaint = new Paint();
mNorthPaint.setColor(Color.BLACK);
mNorthPaint.setStyle(Paint.Style.STROKE);
Expand Down Expand Up @@ -280,6 +279,8 @@ public void setStopped() {

@RequiresApi(api = Build.VERSION_CODES.N)
public void setGnssStatus(GnssStatus status) {
// Use C/N0 instead of SNR - see #65
mUseSnr = false;

if (mPrns == null) {
/**
Expand All @@ -289,7 +290,7 @@ public void setGnssStatus(GnssStatus status) {
*/
final int MAX_LENGTH = 255;
mPrns = new int[MAX_LENGTH];
mSnrs = new float[MAX_LENGTH];
mSnrCn0s = new float[MAX_LENGTH];
mElevs = new float[MAX_LENGTH];
mAzims = new float[MAX_LENGTH];
mConstellationType = new int[MAX_LENGTH];
Expand All @@ -298,7 +299,7 @@ public void setGnssStatus(GnssStatus status) {
int length = status.getSatelliteCount();
mSvCount = 0;
while (mSvCount < length) {
mSnrs[mSvCount] = 0.0f; // This is replaced later by GnssMeasurement.getSnrInDb()
mSnrCn0s[mSvCount] = status.getCn0DbHz(mSvCount);
mElevs[mSvCount] = status.getElevationDegrees(mSvCount);
mAzims[mSvCount] = status.getAzimuthDegrees(mSvCount);
mPrns[mSvCount] = status.getSvid(mSvCount);
Expand All @@ -312,51 +313,19 @@ public void setGnssStatus(GnssStatus status) {

@RequiresApi(api = Build.VERSION_CODES.N)
public void setGnssMeasurementEvent(GnssMeasurementsEvent event) {
if (mPrns == null) {
// We don't have any satellites to store PRNs for yet (no GnssStatus updates) - no op;
return;
}
if (mSnrs == null) {
mSnrs = new float[mPrns.length];
}
if (mSnrsForSats == null) {
mSnrsForSats = new HashMap<>(mPrns.length);
}
mSnrsForSats.clear();

Collection<GnssMeasurement> measurements = event.getMeasurements();

String key;

// Write all SNRs for svid/constellation types to HashMap for easy retrieval
for (GnssMeasurement m : measurements) {
if (m.hasSnrInDb()) {
key = GpsTestUtil.createGnssSatelliteKey(m.getSvid(), m.getConstellationType());
mSnrsForSats.put(key, m.getSnrInDb());
}
}

// Write correct SNR value for the given satellite/constellation to correct value in array
for (int i = 0; i < mPrns.length; i++) {
key = GpsTestUtil.createGnssSatelliteKey(mPrns[i], mConstellationType[i]);
Double snr = mSnrsForSats.get(key);
if (snr != null) {
mSnrs[i] = snr.floatValue();
} else {
mSnrs[i] = 0.0f;
}
}

postInvalidate();
// No-op
}

@Deprecated
public void setSats(GpsStatus status) {
// Use SNR instead of C/N0 - see #65
mUseSnr = true;

Iterator<GpsSatellite> satellites = status.getSatellites().iterator();

if (mSnrs == null) {
if (mSnrCn0s == null) {
int length = status.getMaxSatellites();
mSnrs = new float[length];
mSnrCn0s = new float[length];
mElevs = new float[length];
mAzims = new float[length];
mPrns = new int[length];
Expand All @@ -367,7 +336,7 @@ public void setSats(GpsStatus status) {
mSvCount = 0;
while (satellites.hasNext()) {
GpsSatellite satellite = satellites.next();
mSnrs[mSvCount] = satellite.getSnr();
mSnrCn0s[mSvCount] = satellite.getSnr();
mElevs[mSvCount] = satellite.getElevation();
mAzims[mSvCount] = satellite.getAzimuth();
mPrns[mSvCount] = satellite.getPrn();
Expand Down Expand Up @@ -447,7 +416,7 @@ private void drawNorthIndicator(Canvas c, int s) {
c.drawPath(path, mNorthFillPaint);
}

private void drawSatellite(Canvas c, int s, float elev, float azim, float snr, int prn,
private void drawSatellite(Canvas c, int s, float elev, float azim, float snrCn0, int prn,
int constellationType) {
double radius, angle;
float x, y;
Expand All @@ -456,7 +425,7 @@ private void drawSatellite(Canvas c, int s, float elev, float azim, float snr, i
final double PRN_Y_SCALE = 3.8;
Paint thisPaint;

thisPaint = getSatellitePaint(mSatelliteFillPaint, snr);
thisPaint = getSatellitePaint(mSatelliteFillPaint, snrCn0);

radius = elevationToRadius(s, elev);
azim -= mOrientation;
Expand Down Expand Up @@ -541,42 +510,63 @@ private void drawPentagon(Canvas c, float x, float y, Paint fillPaint) {
c.drawPath(path, mSatelliteStrokePaint);
}

private Paint getSatellitePaint(Paint base, float snr) {
int numSteps;
/**
* Gets the paint color for a satellite based on provided SNR or C/N0
*
* @param base the base paint color to be changed
* @param snrCn0 the SNR to use (if mUseSnr is true) or the C/N0 to use (if mUseSnr is
* false)
* to generate the satellite color based on signal quality
* @return the paint color for a satellite based on provided SNR or C/N0
*/
private Paint getSatellitePaint(Paint base, float snrCn0) {
Paint newPaint;

newPaint = new Paint(base);

numSteps = mSnrThresholds.length;
int numSteps;
final float thresholds[];
final int colors[];

if (mUseSnr) {
// Use SNR
numSteps = mSnrThresholds.length;
thresholds = mSnrThresholds;
colors = mSnrColors;
} else {
// Use C/N0
numSteps = mCn0Thresholds.length;
thresholds = mCn0Thresholds;
colors = mCn0Colors;
}

if (snr <= mSnrThresholds[0]) {
newPaint.setColor(mSnrColors[0]);
if (snrCn0 <= thresholds[0]) {
newPaint.setColor(colors[0]);
return newPaint;
}

if (snr >= mSnrThresholds[numSteps - 1]) {
newPaint.setColor(mSnrColors[numSteps - 1]);
if (snrCn0 >= thresholds[numSteps - 1]) {
newPaint.setColor(colors[numSteps - 1]);
return newPaint;
}

for (int i = 0; i < numSteps - 1; i++) {
float threshold = mSnrThresholds[i];
float nextThreshold = mSnrThresholds[i + 1];
if (snr >= threshold && snr <= nextThreshold) {
float threshold = thresholds[i];
float nextThreshold = thresholds[i + 1];
if (snrCn0 >= threshold && snrCn0 <= nextThreshold) {
int c1, r1, g1, b1, c2, r2, g2, b2, c3, r3, g3, b3;
float f;

c1 = mSnrColors[i];
c1 = colors[i];
r1 = Color.red(c1);
g1 = Color.green(c1);
b1 = Color.blue(c1);

c2 = mSnrColors[i + 1];
c2 = colors[i + 1];
r2 = Color.red(c2);
g2 = Color.green(c2);
b2 = Color.blue(c2);

f = (snr - threshold) / (nextThreshold - threshold);
f = (snrCn0 - threshold) / (nextThreshold - threshold);

r3 = (int) (r2 * f + r1 * (1.0f - f));
g3 = (int) (g2 * f + g1 * (1.0f - f));
Expand Down Expand Up @@ -609,8 +599,8 @@ protected void onDraw(Canvas canvas) {
int numSats = mSvCount;

for (int i = 0; i < numSats; i++) {
if (mSnrs[i] > 0.0f && (mElevs[i] != 0.0f || mAzims[i] != 0.0f)) {
drawSatellite(canvas, minScreenDimen, mElevs[i], mAzims[i], mSnrs[i],
if (mSnrCn0s[i] > 0.0f && (mElevs[i] != 0.0f || mAzims[i] != 0.0f)) {
drawSatellite(canvas, minScreenDimen, mElevs[i], mAzims[i], mSnrCn0s[i],
mPrns[i], mConstellationType[i]);
}
}
Expand Down
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