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)
Related
I have a list of geojson polygons that i am showing on my map, i am trying to determine, based on the current bounds of the map, if any part of the polygon is on the map. Any ideas as far as functions in the api to determine this?
I have tried the bounds.contains() method but it looks like that needs a specific point rather than an area.
Eric, I think you can get a center point of each polygon and set marker to it. So you can use it to represent a polygon.
I am able to display a Google Maps map on a web site and load hundreds of markers for the current map area and display them. The problem is how to behave when the map is zoomed in/out or is moved, so the map area changes.
There is a part of the map that is the same than before, and so are the markers in it. But there is a part of the map that is new and new markers should be added.
Right now I am doing the simplest solution, clearing all markers, retrieving markers for the current map area and add them. This produces a flickery effect on the markers (obviously) due to clear and add immediately after.
What is a efficient way to deal with this situation?
Is there a way to check if a marker has already been added to the map?
You can use a marker cluster or a clustering algorithm to group marker that are close together when you zoom out and ungroup them when you zoom in. It can significantly reduce the database query time and the map drawing. A good solution is a kd-tree.
To check if a marker has been added to the map, call the getMap method of the marker and if it returns a map object, it has been added.
To check if a marker is in the visible area of the map, you can call the getBounds method on the map which returns a LatLngBounds. Then call the contains method of the returned LatLngBounds passing the coordinates of the marker.
Hope this helps
The closest example of what I'm trying to accomplish is a store locator. I have 6,000+ locations that need to be plotted onto a map of Canada.
My original plan was to use Google maps to place markers on each location, but it doesn't make sense to plot them all every time someone attempts to view the map, or various parts of the map.
How does one only put markers on the locations in view? Do I have to send the geo data of all 6000 locations to the client each time they load the map?
Is this doable with maps? (I'm sure it's got to be) Or is there a better service for this kind of thing?
Definitely do not draw all the locations at the same time if they are not all visible. Consider using MarkerManager (article here) or MarkerLight (code: http://gmaps-samples.googlecode.com/svn/trunk/manymarkers/, demo: http://gmaps-samples.googlecode.com/svn/trunk/manymarkers/randommarkers.html). If your initial map and data is such that all the markers would be visible initially, this is definitely the way to go.
You can also use the GEvent object (docs) to detect a "move" event, then check the current display coordinates, draw any that are in bounds. This is the best route if your initial map is too zoomed or small, and/or your marker set is too large to fit on the map's initial view. Your user will be moving the map around, so you can react to that movement and only draw the relevant markers. Take a look at http://econym.org.uk/gmap/gevent.htm for a list of other GEvent events (couldn't find an official list on the API), you might also want to watch "zoom" events.
The two methods can also be combined.
You can use getBounds() to determine the viewable portion of the map. I'd use this data to request from the server all locations within those bounds. Use the bounds_changed event to monitor changes to the viewport and request additional locations as necessary. You'll probably want to set either a minimum zoom level, or maximum number of results to avoid displaying too many locations than is reasonable. Eg, when the map is zoomed out to display all of Canada in a single view.
I have a store locator that displays stores as markers on the map and lists them in a sidebar. There are ~600 stores and they are all loaded at once on the page load via AJAX. So I have access to all them in an array at all times. Now, the functionality I want is that when the user moves/zooms around in the viewport, I get the bounds of the current area being displayed and filter the results in the sidebar (the array of locations, each location has a lat and long) based on whether or not they would be in that area being displayed. Then I would draw the markers of the relevant locations. Basically, whatever locations would be viewable in the viewport would also be listed in the sidebar, staying in sync.
Could someone point me in the right direction to implement this? Does this even sound like an efficient way of handling this functionality?
You need to write a handler for bounds_changed event (more documentation here)
google.maps.event.addListener(map, 'bounds_changed', function(){
// your logic here - map.getBounds() will give you the updated bounds
});
As for efficiency, loading everything at once is probably not the most scalable approach. What if you have 6000 stores next year or you add additional data for every store? A better approach is to pass the bounds back to the server using an AJAX call and only return stores that fall into the area.
You can attach moves/zooms event to the map and basically do a bound check to hide/show markers within the viewing bound. You can achieve this using LatLngBounds(sw?:LatLng, ne?:LatLng) and check the markers LatLng against the map's current bounds using getBounds();. Furthermore within LatLngBounds there's a method to check to see if the LatLtn is within Bounds contains(latLng:LatLng). So you would loop through your markers' LatLng and check against it.
Google Map API LatLngBounds
and
Google Map API Map
As far as the sidebar goes, if you have markers saved then you can just remove or hide the associated locations on the sidebar.
I am developing a Google Maps application and I've run into this problem. I need to remove all markers which are out of bounds from the map.
Is there any simple way of doing this, besides keeping an array and looking at the latlng of each marker?
I cannot use MarkerManager because I have way too many points. I don't want to use clearOverlays() because it would close any open marker.
Any help would be appreciated.
If you don't want to look at each marker individually then cluster them into some sets initially and calculate the bounds of the set.
You can then show or hide the sets depending on what is currently showing on the map (you can find the boundary of the map using GMap2.getBounds() ).
How many points are we talking about?
Update
A. About 65K.
I can see why you can't create 65K GMarkers when the page loads. That will take over 5 seconds.
I'd cluster them into groups of 200 ish and when the edge of the group gets within a 1/4 map width outside of the displayed edge then find, create markers and display the adjacent group. It it goes outside of 1/2 a map width of the outside edge then hide the group.
Other alternatives are to use a third party library such as
Cluster Marker - http://googlemapsapi.martinpearman.co.uk/articles.php?cat_id=1
Clusterer - http://www.acme.com/javascript/#Clusterer