Develop Reference

Expo - increase location accuracy with Geofence

I could really use some help improving the accuracy of the Geofencing feature. If you look at the following screenshots you can see my location and the location of circle and marker which share the same latLng coordiantes and radius as my geofence.
Link to the image
If I run the following lines within the app.js file:
const taskName = "front_door";
const latLng = { latitude: -37.820711, longitude: 144.994264 };
const radius = 5;
Permissions.askAsync(Permissions.LOCATION);
Location.startGeofencingAsync(taskName, [
{
...latLng,
radius
}
]);
TaskManager.defineTask(taskName, task => {
if (task.data.eventType === Location.GeofencingEventType.Enter) {
console.log("entered");
}
console.log(task.data.region.state);
return;
});
Which is returning entered and 1 (explanation).
Given my current location being outside of the geofence I would expect entered to fire only once I had inside of the geofence and task.data.region.state to equal 2 (explanation).
If I change:
const latLng = { latitude: -37.820711, longitude: 144.994264 };
To:
const latLng = { latitude: -37, longitude: 144 };
The geofence is far enough away that entered is never output and the task.data.region.state equals 2.
This leads me to believe that the issue is related to the accuracy set of Location however, I cannot find a way to increase the accuracy when using the startGeofencingAsync method.
If I was not using geofencing I would do something like this:
Location.startLocationUpdatesAsync(taskName, {
accuracy: Location.Accuracy.Highest
});
But I can't see how to access the options object when using Location.startGeofencingAsync(taskName, regions)
If you know how to achieve this please do let me know as I am pulling my hair out over it! Thanks in advance :)

How can I convert Google Maps plus codes to Lng & Lat coordinates

I'm working on a project and I'm using some old google maps stuff. It requires longitude and latitude gps coordinates to get the location of a hospital for example.
I can't find a way to retrieve that info in this format 'lng,lat'
For example: (34.417514, 8.7518123)
The only thing the new google maps has is plus codes (used by https://plus.codes/) which they use as the location coordinates.
Can you guys help me find out a way to convert them to lng lat format or a way to retrieve the lng and lat from Google Maps website directly.
Or an alternative by saving my geolocation in a plus codes format in android studio (in a database of course) instead of using lat lng
https://www.up-00.com/i/00125/m4kadq6c7aeb.png

You can convert Plus Codes into lat/lng format via Plus codes API. If you have full (8-digits before "+" character, e.g. 8F6CCQCW+2F for your location) Plus Code, you can locally (without any internet request) use OpenLocationCode.decode() method this way:
...
OpenLocationCode olc = new OpenLocationCode("8F6CCQCW+2F");
Log.d(TAG, "Lat = " + olc.decode().getCenterLatitude() + " Lng = " + olc.decode().getCenterLongitude());
...
If you have short Plus Code (less than 8 digits before "+" character, e.g. CCQCW+2F Gafsa for your location, Gafsa is the area and it's used instead of using the full plus code) you can use HttpURLConnection with
`https://plus.codes/api?address=CCQCW%2B2F Gafsa&key=YOUR_GEOCODING_API_KEY`
(%2B is for the for + symbol)
(NB! you need Geocoding API Key for geocode Gafsa part, which is the area, you need an area with a short plus code)
and get location.lat and location.lng tags from its JSON response:
{
"plus_code": {
"global_code": "8F6CCQJG+",
"geometry": {
"bounds": {
"northeast": {
"lat": 34.432500000000005,
"lng": 8.777500000000003
},
"southwest": {
"lat": 34.43000000000001,
"lng": 8.775000000000006
}
},
"location": {
"lat": 34.431250000000006,
"lng": 8.776250000000005
}
},
"locality": {}
},
"status": "OK"
}
For "alternative" (saving my geolocation in a plus codes format) you can (fully local) use encode() method of OpenLocationCode class:
OpenLocationCode.encode(34.43125, 8.77625)

Python solution:
>>> import openlocationcode
>>> openlocationcode.decode('8F6CCQCW+2F')
[34.42, 8.796125, 34.420125, 8.79625, 34.4200625, 8.7961875, 10]

Python implementation
from openlocationcode import openlocationcode as olc
olc.decode("8F6CCQCW+2F")
Output:
[34.42, 8.796125, 34.420125, 8.79625, 34.4200625, 8.7961875, 10]

Mark in google maps a list of addresses - Android or PHP

I have a list of addresses and I want to mark this places all in google maps(nearly 1k), getting maybe its cordinates to save them.
Actually I am not programming an app, but I know both lenguages (Android and PHP) and I think it is possible to do this with both. Any idea ? Thank in advance!

Have you tried the google maps api?
https://developers.google.com/maps/documentation/geocoding/intro
https://developers.google.com/maps/documentation/geocoding/intro#ReverseGeocoding
This is what you are looking for I think.
EDIT: to mark stars on map
// In the following example, markers appear when the user clicks on the map.
// Each marker is labeled with a single alphabetical character.
var labels = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
var labelIndex = 0;
function initialize() {
var bangalore = { lat: 12.97, lng: 77.59 };
var map = new google.maps.Map(document.getElementById('map'), {
zoom: 12,
center: bangalore
});
// This event listener calls addMarker() when the map is clicked.
google.maps.event.addListener(map, 'click', function(event) {
addMarker(event.latLng, map);
});
// Add a marker at the center of the map.
addMarker(bangalore, map);
}
// Adds a marker to the map.
function addMarker(location, map) {
// Add the marker at the clicked location, and add the next-available label
// from the array of alphabetical characters.
var marker = new google.maps.Marker({
position: location,
label: labels[labelIndex++ % labels.length],
map: map
});
}

OSMdroid how to get screen coordinates?

I am doing app on android using osmdroid. How I can get coordinates(top, bottom, left,right) of map which is shown on screen?
Thanx.

It is not completely clear what you're asking, but I think you're asking for the lat/lon bounding box.
BoundingBoxE6 boundingBox = mMapView.getProjection().getBoundingBox();

"I do it in onCreate if it important" => Yes, it is.
In fact, you cannot access to a correct mapview bounding box in onCreate.
This is "because the MapView's width and height is zero because it hasn't had onLayout called yet"
This is a (quite annoying) osmdroid issue, not fixed in v4.2.
In addition, when called in onCreate, setCenter is also not working properly in v4.2.
See more explanation and workarounds here: https://github.com/osmdroid/osmdroid/issues/22

In react-native I use the onRegionChangeComplete event (onRegionChangeComplete={e => properties.regionChange(e)}). This event returns the region of the MapView. So: {"latitude": 4.50751184289841, "latitudeDelta": 0.09999884159289252, "longitude": -75.67515761717539, "longitudeDelta": 0.06322002503726765}
So, if you need to calculate a polygon with the screen area, you should do the following:
regionChange = (e) => {
areaLoadData = [
{
latitude: e.latitude + e.latitudeDelta,
longitude: e.longitude - e.longitudeDelta
},
{
latitude: e.latitude + e.latitudeDelta,
longitude: e.longitude + e.longitudeDelta
},
{
latitude: e.latitude - e.latitudeDelta,
longitude: e.longitude + e.longitudeDelta
},
{
latitude: e.latitude - e.latitudeDelta,
longitude: e.longitude - e.longitudeDelta
},
]
}

Map View errors when I used it for the second time in Android (Titanium)

I have records on the table list contains data that has latitude & longitude on the listing widow. When I click on each row, it passes to the detail window that display the mapview and its annotation of that record.
I zoom in & out, moved to different area and I clicked "back" button to go back to the record list.
Then, I selected on the different record to see the map on the detail window again, when I'm on the detail window suddenly I clicked on the map, there, it alerts me an error message which did not mention about the specific issues.
Here is my code:
self.listingAnnotation = Titanium.Map.createAnnotation({
pincolor: Titanium.Map.ANNOTATION_RED,
latitude: latitude,
longitude: longitude,
animate: true
});
self.region = {
latitude: latitude,
longitude: longitude
};
if(!self._mapview){
self._mapview = Titanium.Map.createView({
top: 130,
bottom: 0,
animate:true,
mapType: Titanium.Map.STANDARD_TYPE,
region: {latitude: latitude, longitude: longitude},
annotations: [self.listingAnnotation]
});
}
else{
self._mapview.removeAllAnnotations();
self._mapview.setLocation(self.region);
self._mapview.addAnnotation(self.listingAnnotation);
}
self._listingDetailWindow.add(self._mapview);