Get co-ordinates range while using leaflet - google-maps

My application is in Angular 5. I am calling an API and get different data along with latitude & longitude. When I fetch these data, I am rendering markers on map based on lats & longs got from API using Leaflet I have created Marker Cluster to display markers in better way. You can imagine that markers displayed properly and its working.
Now I want to implement filter when I do ZoomIn & ZoomOut
I.e. When I zoomIn / zoomOut in map, it will cover some area right? I want those co-ordinates of covered area. By that range of co-ordinates I will execute API and get filtered results for that area only.
Any help?
Thanks in Advance

Use the getBounds() method on your Leaflet map object to obtain a LatLngBounds which describes the visible area of your map. You can use its values to feed your API query.
var bounds = mymap.getBounds()
Documentation at http://leafletjs.com/reference-1.3.0.html#map-methods-for-getting-map-state

Related

How to get bounds of visible map with flutter google_maps plugin?

I'm trying to find out what is the bounding box of the visible part of google map in flutter's google maps plugin.
Is it possible to get it?
If not is it possible to calculate the bounding box based on zoom level and latitude, longitude of the map center?
That would be GoogleMapController.getVisibleRegion()
Be careful, GoogleMapController.getVisibleRegion() returns a LatLngBounds (a rectangle) and if your map has a tilt then it should not be a rectangle but a trapezoid!
The issue is in the plugin implementation where the returned result is computed only from latLngBounds field whereas it should be computed from farLeft, farRight, nearLeft, nearRight fields.
Reference: https://developers.google.com/maps/documentation/android-sdk/reference/com/google/android/libraries/maps/model/VisibleRegion
So GoogleMapController.getVisibleRegion() is not accurate and can't be used if there's a tilt.
For reference, an issue has been created: https://github.com/flutter/flutter/issues/74888

Getting coordinates of polygon areas defined in KML

I have displayed a google map using a KML file as source. The map has a number of polygon areas marked in it. Is there any way to get the center coordinates of each of the polygons without the click event ? I need to display an info window above each polygons when the map is displayed.
Thanks
google.maps.KmlLayer is uses tile based rendering, you can't (at least at present) access the coordinates of the polygons except on a click.
You could use:
FusionTablesLayer, import your KML into that, then query it using either a Fusion Tables API v1.0 or a google.visualization (GViz) query) for the coordinates to get their center.
example using FusionTablesLayer and GViz
A third party KML parser like geoxml3 or geoxml-v3 to render the polygons as native google.maps.Polygon objects, and get their center. This will have performance issues with complex KML.
example using geoxml3

algorith or formula to get a set of lat lon values based on viewport and zoomlevel

I need to display around 50,000 markers on the map. But i was able to plot only 10000 points. I thought of implementing this way correct me if i'm wrong...
Instead of fetching whole data at once just fetch points that are in the viewport and depending on the zoomlevel.
ex:google maps: at one zoomlevel only states are shows if we zoom in further cities are shown
I'm stuck with the zoomlevel.. how to relate zoomlevel and viewport.Is there any algorithm or formulae that helps in getting the lat long values or it needs to be hardcoded in the database like for particular lat-lon this is the zoomlevel range so while fetching range is checked.
i'm using openlayers bbox feature to get the bounds
Thanx in advance
google.maps.Map.getBounds() will return the lat/long bounds of the viewport.
50,000 markers is a lot compared to what Google Maps can handle; you would have to be way zoomed in to have few enough markers to be under the limits. You might do better by creating custom tiles with dots instead of markers. You can see an example at
http://maps.webfoot.com/demos/election2008/
Scroll down to the third overlay to see dots; select zip codes to see LOTS of dots.

google map zoom after directions

I am using google maps in order to give some directions from one point to another.
Although, I have set the zoom of the map to 15 the zoom changes after the response of the direction request in order probably to fit the directions into the map.
Does anyone nows how to keep the zoom constant at 15. and focus at the first point?
See the documentation for the DirectionsRenderer
preserveViewport: true
will prevent the DirectionsRenderer from changing the zoom.
To center the map on the first point use the map.setCenter function. You will need to parse the response from the directions service and create a google.maps.LatLng object for the first point.
This example shows one way to parse the response:
http://www.geocodezip.com/v3_directions_custom_iconsC.html
(you don't need everything, just the location of the point you want to center on)

Get or create a polygon based on LatLong

I am really new to google maps and need some help.
I am calling a 3rd party api that requires a polygon to return markers.
I am not sure how to do this. Basically I want to be able to pass in a LatLong and return a polygon based on the window size and zoom level.
Is this possible?
Thank you for your time.
Sounds like the app needs the bounds of the map viewport.
Look at the documentation for the getBounds method of the google.maps.Map class.