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Android Location Bias in autocomplete Rectangular Bounds

I want the autocomplete result to show only 1 km from the user location.
there is a way with RectangularBounds:
setLocationBias(RectangularBounds.newInstance(
new LatLng(-33.880490, 151.184363),
new LatLng(-33.858754, 151.229596)))
There are only 2 points here. How does it make a rectangular?
If the user Latlng is for example 32.0000000, 30.0000000 , How can I do a RectangularBounds of 1 km around him?

For the first question if you look at the docs
RectangularBounds newInstance (LatLng southwest, LatLng northeast)
Is rectangular because it represents two coordinates: southwest and northeast, that's usually refered as a Bounding Box (or shortened to bbox) and represents the area inside that two coordinates.
The second question is less simple and there is more than one way of doing it.
One approach is to find out a method to add a distance to a coordinate, this methods are always approximate. For this LatLng geographic coordinates you could use:
public static LatLng getCoordinate(double lat0, double lng0, long dy, long dx) {
double lat = lat0 + (180 / Math.PI) * (dy / 6378137);
double lng = lng0 + (180 / Math.PI) * (dx / 6378137) / Math.cos(lat0);
return new LatLng(lat, lng);
}
where lat0 and long0 are the original coordinates and dx and dy are a distance in meters (as the Earth radius is set in meters 6378137).
And now you can create an aproximate bounding box with the original point +- 1000 meters. Supposing the point you set as starting point is at latitude -33.869622 and longitude 151.206979 the bbox would be:
RectangularBounds.newInstance(
getCoordinate(-33.869622, 151.206979, -1000, -1000),
getCoordinate(-33.869622, 151.206979, 1000, 1000))
That is the bbox you could use for the api call.
In case you have an instance variable named currentlocation this will be:
RectangularBounds.newInstance(
getCoordinate(this.currentlocation.getLatitude(), this.currentlocation.getLongitude(), -1000, -1000),
getCoordinate(this.currentlocation.getLatitude(), this.currentlocation.getLongitude(), 1000, 1000))
If you still need to be more precise with the 1km distance and discard points that are inside that square (bbox) but out of circle of 1km radius you could filter the results by checking the distance to the original point before returning the result or displaying it.
As a curiosity
Another way I could think of is to change the coordinate's projection to another one to make the calculations easier, if you transform the coordinate to mercator adding 1000 to the x value would add 1 km and adding 1000 to the y would also add 1 km as it uses meters as unit, but then you should transform back to the original projection (working with LatLng) as it's the one that api is using so I don't think it's worth it, but it should work as well.

Android - Google Maps API Heatmap with fixed radius in meters

The Heatmap Overlay for the Android Google Maps API renders the radius in pixels, which means that by zooming in and out the radius gets bigger and smaller.
I need a heatmap with fixed radius (e.g. in meters instead of pixels) that does not rescale when zooming in and out.
Is there any possibility to do so?

In googlemap api, get scale data. In UI you have the legend which states the map scale. Something like this - (check in google maps bottom right I'm talking about 2000Ft thing below)
You know cm length of the phone screen, you know the pixels in complete width,so
cm(phoneScreen) --> cm/pixel ratio --> pixel radius to cm radius.
you can deduce using some maths I suppose.

As for my opinion you can use setRadius() method to change the radius of heatmaps location in response to changed zoom. Something like this:
int DEFAULT_ZOOM_LEVEL = 10;
int ZOOM_STEP_FOR_RADIUS = 2;
mProvider = new HeatmapTileProvider.Builder()
.data(mList)
.setRadius(DEFAULT_ZOOM_LEVEL)
.build();
mOverlay = mMap.addTileOverlay(new TileOverlayOptions().tileProvider(mProvider));
mMap.setOnCameraIdleListener(new GoogleMap.OnCameraIdleListener({
#Override
void onCameraIdle() {
float newZoom = mMap.getCameraPosition().zoom;
mProvider.setRadius(DEFAULT_ZOOM_LEVEL + newZoom * ZOOM_STEP_FOR_RADIUS)
mOverlay.clearTileCache();
}
});

Calculate height above map given zoom level in google maps

I am trying to calculate the height above map (ignoring topography) given a zoom level. I know the equation for scale at a specific zoom level is 591657550.5/2^(level-1) (https://gis.stackexchange.com/questions/7430/google-maps-zoom-level-ratio), but I am unsure on how to use this information (or whether or not this is the right information) to solve for height above map. Any help is appreciated.

I set my google map size to 5cm selected a zoom level, and then re-found that location with that zoom in google earth to get a eye altitude level (the D value in the angular size equation http://en.wikipedia.org/wiki/Forced_perspective). I was able to find the h value in the angular size equation by first setting my map length on screen to 5cm, and then using the scale equation of 591657550.5/2^(level-1) *5cm to calculate the h value in the angular size equation. Knowing these two variables I was able to calculate the constant angle for which google maps displayed images when maps was at a 5cm width (85.36222058). From these pieces of information I was able to construct this method which calculates eye altitude above map from zoom level with relative accuracy
public float getAltitude(float mapzoom){
//this equation is a transformation of the angular size equation solving for D. See: http://en.wikipedia.org/wiki/Forced_perspective
float googleearthaltitude;
float firstPartOfEq= (float)(.05 * ((591657550.5/(Math.pow(2,(mapzoom-1))))/2));//amount displayed is .05 meters and map scale =591657550.5/(Math.pow(2,(mapzoom-1))))
//this bit ^ essentially gets the h value in the angular size eq then divides it by 2
googleearthaltitude =(firstPartOfEq) * ((float) (Math.cos(Math.toRadians(85.362/2)))/(float) (Math.sin(Math.toRadians(85.362/2))));//85.362 is angle which google maps displays on a 5cm wide screen
return googleearthaltitude;
}
Sorry if my explanation is poorly explained. If you guys want to use this method feel free to. Sorry for any poorly worded sentences.

I have basically converted Javascript code to Java. I hope this works.
public int convertRangeToZoom(double range) {
//see: google.maps.v3.all.debug.js
int zoom = (int) Math.round(Math.log(35200000 / range) / Math.log(2));
if (zoom < 0) zoom = 0;
else if (zoom > 19) zoom = 19;
return zoom;
}
public int convertZoomToRange(double zoom){
//see: google.maps.v3.all.debug.js
int range = (int) 35200000/(Math.pow(2, zoom));
if (range < 300) range = 300;
return range;
}
https://groups.google.com/forum/#!msg/google-earth-browser-plugin/eSL9GlAkWBk/T4mdToJz_FgJ

Determine a reasonable zoom level for Google Maps given location accuracy

I am trying to center a Google Map to the user location while giving a reasonable zoom level taking into account the accuracy of that location. Could anybody describe how should I compute it? Which variables are involved, how do you achieve this?

What you are looking for is the formula that calculates the zoom level based on the accuracy of the location.
I managed to come up with this formula which (in my tests) worked pretty well.
This can be simplified (might not seem so) to this:
This scary looking thing is what you want.
EquatorLength is 40,075,004 meters. While the Meters/Pixel can be calculated by diving the diameter of the accuracy circle by the length of the device screen (in pixels).
Here's a sample program that I used to test this formula:
GoogleMap mMap;
#Override
protected void onStart() {
super.onStart();
mMap = ((MapFragment)getFragmentManager().findFragmentById(R.id.map)).getMap();
// Enable user's location layer
mMap.setMyLocationEnabled(true);
mMap.setOnMyLocationChangeListener(new GoogleMap.OnMyLocationChangeListener() {
#Override
public void onMyLocationChange(Location location) {
// Location lat-lng
LatLng loc = new LatLng(location.getLatitude(), location.getLongitude());
// Location accuracy diameter (in meters)
float accuracy = location.getAccuracy() * 2;
// Screen measurements
DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics);
// Use min(width, height) (to properly fit the screen
int screenSize = Math.min(metrics.widthPixels, metrics.heightPixels);
// Equators length
long equator = 40075004;
// The meters per pixel required to show the whole area the user might be located in
double requiredMpp = accuracy/screenSize;
// Calculate the zoom level
double zoomLevel = ((Math.log(equator / (256 * requiredMpp))) / Math.log(2)) + 1;
Log.e(TAG, String.format("Accuracy: %f. Screen Width: %d, Height: %d",
accuracy, metrics.widthPixels, metrics.heightPixels));
Log.e(TAG, String.format("Required M/Px: %f Zoom Level: %f Approx Zoom Level: %d",
requiredMpp, zoomLevel, calculateZoomLevel(screenSize, accuracy)));
// Center to user's position
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(loc, (float) zoomLevel));
// Prevent the camera centering on the user again
mMap.setOnMyLocationChangeListener(null);
}
});
}
private int calculateZoomLevel(int screenWidth, float accuracy) {
double equatorLength = 40075004; // in meters
double metersPerPixel = equatorLength / 256;
int zoomLevel = 1;
while ((metersPerPixel * (double) screenWidth) > accuracy) {
metersPerPixel /= 2;
zoomLevel++;
}
return zoomLevel;
}
Few things to note:
This answer is based on this and implements it to check the values generated
Accuracy is the radius of user's location and according to the docs it can be up to 68% correct.
Any corrections are very welcome.

If you're looking for something simple:
var zoom = Math.min(20, Math.max(1, Math.log2(591657550/accuracy)-2));
Tweak -2 to get the desired zoom.
Checkout this answer for a chart corresponding zoom with accuracy.

Thanks #Simas! I picked up your algo to make this extension to GMSMapView to calculate for the ideal zoomLevel given the accuracy of a CLLocation.
I had to make adjustments to consider devices with Retina displays since each pixel is not exactly the same as 1 point on the screen:
extension GMSMapView {
func getIdealZoomLevel(usingLocation location:CLLocation)->Float {
let retinaScale = Double(UIScreen.mainScreen().scale)
let equatorLength : Double = 40075004 // in meters
var metersPerPixel = equatorLength / 256
let accuracy = location.horizontalAccuracy
// I used height because I'm on landscape, but moving forward I'll have to get the Min of the width and height.
// I also took only 75% of the height to give it some margin
let screenWidth : Double = Double( self.frame.size.height) * 0.75
var display = metersPerPixel * (screenWidth / retinaScale)
var zoomLevel : Float = 0.0
while (display > accuracy) {
metersPerPixel /= 2
display = metersPerPixel * (screenWidth / retinaScale)
zoomLevel += 1
}
return zoomLevel
}
}
It's for a Swift project I'm working on and right now, I'm able to display a good proximity enclosing the radius within the given CLLocation.
Hope this helps.

Setting the zoom level of worldwind map

I am trying to setup a layer using worldwind java and i want to render icons on the map at their specific geo locations. I have that working but i want to be able to zoom to where all the icons are. Is there an easy way to do that? Im not really sure where to start.. Are there existing methods for zooming in on a group of points?

First you need to calculate the Sector containing all of your points. e.g.
Sector boundingSector = Sector.boundingSector(points);
//public static Sector boundingSector(Iterable<? extends LatLon> itrbl)
Now here's some code taken from ScankortDenmark example to calculate the zoom you need to fit the whole sector on screen:
// From ScankortDenmark example
public static double computeZoomForExtent(Sector sector)
{
Angle delta = sector.getDeltaLat();
if (sector.getDeltaLon().compareTo(delta) > 0)
delta = sector.getDeltaLon();
double arcLength = delta.radians * Earth.WGS84_EQUATORIAL_RADIUS;
double fieldOfView = Configuration.getDoubleValue(AVKey.FOV, 45.0);
return arcLength / (2 * Math.tan(fieldOfView / 2.0));
}

182Much's answer does work under under some conditions. However, a better solution must take into account that the Horizontal FOV (Field of View) is not always fixed at 45.0 degrees. It also needs to take into account the Vertical FOV. Even how the positions end of clustering has to be taken into account. Meaning, do the positions spread out more East to West or North and South. Is the users view of the globe (WorldWindow) actually skinnier then the height. All of these factors come into account when calculating the needed zoom level to view all positions. I created this static method to account for all of the listed positions above. As a side note, you can have slightly better precision if you calculate the actual mean radius of the Earth for where your positions tend to cluster instead of taken Earth.WGS84_EQUATORIAL_RADIUS. But this is almost negligible so I leave that part out here.
/**
* Calculates the altitude in meters needed to view all of the given points.
* This method is safe for any window sizing configurations. If the
* WorldWindor arg is null then a static max altitude value of 1,0667,999
* meters is returned. if the WorldWindow is good but the list of Positions
* is null or empty then the current zoom level of the WorldWindow is
* returned. If the list of positions cannot all be seen on the globe
* because some positions are on the other side of the globe then a static
* max altitude value of 1,0667,999 meters is returned.
*
* #param positions
* - a list of positions wanted to view
* #return the altitude in meters needed to view all of the given points.
*/
public static double getZoomAltitude(List<Position> positions, WorldWindow wwd) {
double zoom = 10667999;
if (wwd != null) {
// Gets the current zoom as a fail safe to return
BasicOrbitView orbitView = (BasicOrbitView) wwd.getView();
zoom = orbitView.getZoom();
// zoom is in meters and and is limited the max zoom out to 10,667,999 meters
int MAX_ZOOM = 10667999;
if (positions != null && !positions.isEmpty()) {
Sector sector = Sector.boundingSector(positions);
if (sector != null) {
// This calculation takes into account the window sizing configuration of the map in order to accurately
// display the list of positions.
double meanRadius = Earth.WGS84_EQUATORIAL_RADIUS;
// Next we must calculate the zoom levels for both delta latitude viewing and delta longitude viewing.
// generally, a group of positions that spread out more Longitudenal viewing (wider viewing width)
// holds a constant 45.0 degree field of view (FOV). The horizontal FOV can be changed so this input
// must handle dynamically as well. The latitudenal (positon group runs more East to West then North and South)
// position group have a dynamic FOV that changes depending on the users sizing of the map. These have
// to be handled any time the group of positions has a greater delta latitude than delta longitude.
// Also if the user has a skinny map this will effect the output calculation and must be handled.
// Here we take all the dynamic variables into account for both types of possibilities and choose
// the larger zoom level of them.
int deltaLon = new BigDecimal(sector.getDeltaLon().radians * meanRadius).intValue();
int deltaLat = new BigDecimal(sector.getDeltaLat().radians * meanRadius).intValue();
System.out.println("deltaLonAL Wider: " + deltaLon + "\tdeltaLatAL Taller: " + deltaLat);
double horizontalFOV = orbitView.getFieldOfView().getDegrees();
double verticalFOV = ViewUtil.computeVerticalFieldOfView(orbitView.getFieldOfView(),
orbitView.getViewport()).getDegrees();
double lonZoomLevel = new BigDecimal((deltaLon / 2.0) / (Math.tan(horizontalFOV / 2.0))).intValue();
double latZoomLevel = new BigDecimal((deltaLat / 2.0)
/ (Math.tan(Math.toRadians(verticalFOV) / 2.0))).intValue();
System.out
.println("LonZoomLevel Wider: " + lonZoomLevel + "\tLatZoomLevel Taller: " + latZoomLevel);
double zoomLevel = Math.max(lonZoomLevel, latZoomLevel);
System.out.println("zoomLevel meters: " + zoomLevel + "\tfeet: "
+ new BigDecimal(zoomLevel * 3.2808));
// zoom is the altitude measured in meters to view a given area calculated to fit the viewing
// window edge to edge. A buffer is needed around the area for visual appeal. The bufferedZoom
// is a calculated linear equation (y = 1.0338x + 96177 where R² = 1) It gives the same buffer
// boundary around a group of position depending on the calculated zoom altitude.
double bufferedZoom = 1.0338 * zoomLevel + 96177;
zoom = new BigDecimal(bufferedZoom).intValue();
if (zoom > MAX_ZOOM) {
zoom = MAX_ZOOM;
System.out.println("MAX_ZOOM applied");
}
}
} else {
System.out.println("getZoomAltitude method cannot calculate the zoom because the points passed in was null and the current zoom was returned.");
}
}
return zoom;
}