Develop Reference

Set zoom level of google map based on different lat and long

I have different sites drawn on google map(basically polygon/circle). A site can be anywhere in the world on google map. I have center lat and long of sites(polygon/circle) in an array and I want to set the zoom level of the map so that all the sites can be seen in one view.
For e.g. if there is only one site to display in map, zoom level should be more.
Please help me in this. I am looking for javascript code.

try this hint
var latlngBounds = new google.maps.LatLngBounds();
array of latlng object;
for(i=0;i<array.length;i++){
latlngBounds.extend(array[i]);
}
map.fitBounds(latlngBounds);

adding marker to map in NativeScript app

I'm building a NativeScript app using the nativescript-google-maps-sdk.
I have added an eventlistener for the coordinateTapped event and now that it is working I want to plot a marker on the map at the position at which I tap.
I cannot find an example of this online or in the sdk documentation.
I feel I am very close and just have a few minor corrections to make.
var mapsModule = require("nativescript-google-maps-sdk");
function onCoordinateTapped(args) {
console.log("coordinate tapped!");
var mapView = args.object;
var marker = new mapsModule.Marker();
marker.position = mapsModule.Position.positionFromLatLng(args.latitude,args.longitude);
mapView.addMarker(marker);
}
Note: I've labelled this question with the google-maps tag as there is no nativescript-google-maps tag.

Never it's too late to answer this kind of questions.
The problem was that the args object doesn't have a latitude nor a longitude attribute, so you are trying to add a marker with latitude and longitude as undefined.
Inside your function onCoordinateTapped(args) you can access to two different positions.
First, args.object.latitude and args.object.longitude.
var lat = args.object.latitude;
var lng = args.object.longitude;
Those attributes stand for the current position of the map (you know, the center of it).
Second, args.position.latitude and args.position.longitude.
var lat = args.position.latitude;
var lng = args.position.longitude;
In this case, those attributes represents the actual position of your tap on the map.
Also, this works on coordinateLongPress.

Hey #Danoram you code looks'n'feels right and although there is no XML file I guess you have used the coordinateEvent to pass the fallback function onCoordinateTapped like here
<maps:mapView coordinateTapped="onCoordinateTapped" />
Is that working out for you or are you experiencing some kind of error/unexpected behaviour? It is not entirely clear from your post where the issue is...

How to find center of google map polyline having more than two cordinates?

I am working on asp.net mvc 3 project we are using Google maps.I want to display marker at center of poly line.
I am using below code
var start = new google.maps.LatLng(
MyMapCordinates[0].lat(),
MyMapCordinates[0].lng()
);
var End = new google.maps.LatLng(
MyMapCordinates[MyMapCordinates.length - 1].lat(),
MyMapCordinates[MyMapCordinates.length - 1].lng()
);
debugger
var inBetween = google.maps.geometry.spherical.interpolate(start, End, 0.5);
var marker= new google.maps.Marker({
position: inBetween
});
It is working fine with polyline having two coordinates. But it fails for polyline with more than three co-ordinates. Please suggest

The interpolate method is designed only to work with two sets of coordinates. The computeLength() method looks like what you are looking for to calculate the distance of multiple points, and then just do some math to find the middle.
Does that help?

OpenLayers is showing 720 degree around the globe

My current OpenLayers looks like the following:
a wrong map http://i1179.photobucket.com/albums/x384/yoyomyo/Picture2.png
It has twice as many continents as there should be.
I was trying to set Bounds to my map, but the entire map just refuses to render:
var map = new OpenLayers.Map('map', {restrictedExtent: new OpenLayers.Bounds(-180, -90, 180, 90)});
var layer = new OpenLayers.Layer.OSM( "Simple OSM Map");
map.addLayers([layer]);
map.setCenter(
new OpenLayers.LonLat(-71.147, -42.472).transform( new OpenLayers.Projection("EPSG:4326"),map.getProjectionObject()),
12);
Does any Map guru know what I did wrong?

WrapDateLine
Try wrapDateLine:false

It sounds like you want to set maxExtent.
http://trac.osgeo.org/openlayers/wiki/SettingZoomLevels
Otherwise I have no clue. :)

It would be easier to answer with an example to work off of. I would zoom in 12 is pretty far out. And yes you can zoom in on OSM http://www.openstreetmap.org/
In that site, they use these values
var centre = new OpenLayers.LonLat(-0.1, 51.5);
var zoom = 5;
setMapCenter(centre, zoom); //It calls map.setCenter()

Okay I give up. I think this is just the way OpenStreetMap displays its map.
I have seen many demos and they are all like the one above.

how to redraw markers without redrawing the map? google maps

I currently have a implementation where some markers coming from JSON list is shown, on a particular area, Now I want to filter these marker depending upon some criteria, I have done the filtering part, and got the filtered list. Now to render this markers on the map again, The current implementation loads the js with a key again, also creates the GMap2 object and draws the list of marker on the newly created map, which is really annoying. I want map to be there and only markers to be added and removed from the map.
Any help is appreciated

You can use addOverlay and removeOverlay to add/remove markers from an already displayed map. See the examples here: http://code.google.com/apis/maps/documentation/overlays.html#Markers
var latlng = new GLatLng(lat, lng);
map.addOverlay(new GMarker(latlng));

You can make drawMap() and drawMarkers() as two separate functions. And after map has been created redefine drawMap to empty function like this:
drawMap = function(){}; After that only drawMarkers() will be executed.
Hope this is what you need. If not, provide some code.