Google maps API V3 - multiple markers on exact same spot

Question

Bit stuck on this one   I am retrieving a list of geo coords via JSON and popping them onto a google map   All is working well except in the instance when I have two or more markers on the exact same spot   The API only displays 1 marker - the top one   This is fair enough I suppose but would like to find a way to display them all somehow   I ve searched google and found a few solutions but they mostly seem to be for V2 of the API or just not that great   Ideally I d like a solution where you click some sort of group marker and that then shows the markers clustered around the spot they are all in   Anybody had this problem or similar and would care to share a solution

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The answers above are more elegant  but I found a quick and dirty way that actually works really really incredibly well  You can see it in action at www buildinglit com   All I did was add a random offset to the latitude and longditude to my genxml php page so it returns slightly different results each time with offset each time the map is created with markers  This sounds like a hack  but in reality you only need the markers to move a slight nudge in a random direction for them to be clickable on the map if they are overlapping  It actually works really well  I would say better than the spider method because who wants to deal with that complexity and have them spring everywhere  You just want to be able to select the marker  Nudging it randomly works perfect   Here is an example of the while statement iteration node creation in my php genxml php  while   row    mysql fetch assoc  result     offset   rand 0 1000  10000000   offset2   rand 0  1000  10000000   node    dom- gt createElement  marker     newnode    parnode- gt appendChild  node    newnode- gt setAttribute  name    row  name      newnode- gt setAttribute  address    row  address      newnode- gt setAttribute  lat    row  lat      offset    newnode- gt setAttribute  lng    row  lng      offset2    newnode- gt setAttribute  distance    row  distance      newnode- gt setAttribute  type    row  type      newnode- gt setAttribute  date    row  date      newnode- gt setAttribute  service    row  service      newnode- gt setAttribute  cost    row  cost      newnode- gt setAttribute  company    company     Notice under lat and long there is the  offset  from the 2 variables above  I had to divide random by 0 1000 by 10000000 in order to get a decimal that was randomly small enough to just barely move the markers around  Feel free to tinker with that variable to get one that is more precise for your needs

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Ignatius most excellent answer  updated to work with v2 0 7 of MarkerClustererPlus    Add a prototype click method in the MarkerClusterer class  like so - we will override this later in the map initialize   function      BEGIN MODIFICATION  around line 715  MarkerClusterer prototype onClick   function          return true         END MODIFICATION  In the ClusterIcon class  add the following code AFTER the click clusterclick trigger      EXISTING CODE  around line 143  google maps event trigger mc   click   cClusterIcon cluster    google maps event trigger mc   clusterclick   cClusterIcon cluster       deprecated name     BEGIN MODIFICATION var zoom   mc getMap   getZoom       Trying to pull this dynamically made the more zoomed in clusters not render    when then kind of made this useless  -NNC   BNB    var maxZoom   mc getMaxZoom    var maxZoom   15     if we have reached the maxZoom and there is more than 1 marker in this cluster    use our onClick method to popup a list of options if  zoom  gt   maxZoom  amp  amp  cClusterIcon cluster  markers  length  gt  1        return mc onClick cClusterIcon        END MODIFICATION  Then  in your initialize   function where you initialize the map and declare your MarkerClusterer object   markerCluster   new MarkerClusterer map  markers      onClick OVERRIDE markerCluster onClick   function clickedClusterIcon       return multiChoice clickedClusterIcon cluster         Where multiChoice   is YOUR  yet to be written  function to popup an InfoWindow with a list of options to select from  Note that the markerClusterer object is passed to your function  because you will need this to determine how many markers there are in that cluster  For example   function multiChoice clickedCluster      if  clickedCluster getMarkers   length  gt  1             var markers   clickedCluster getMarkers           do something creative      return false        return true

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Check out Marker Clusterer for V3 - this library clusters nearby points into a group marker  The map zooms in when the clusters are clicked  I d imagine when zoomed right in you d still have the same problem with markers on the same spot though

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Updated to work with MarkerClustererPlus     google maps event trigger mc   click   cClusterIcon cluster      google maps event trigger mc   clusterclick   cClusterIcon cluster       deprecated name       BEGIN MODIFICATION   var zoom   mc getMap   getZoom         Trying to pull this dynamically made the more zoomed in clusters not render      when then kind of made this useless  -NNC   BNB      var maxZoom   mc getMaxZoom      var maxZoom   15       if we have reached the maxZoom and there is more than 1 marker in this cluster      use our onClick method to popup a list of options   if  zoom  gt   maxZoom  amp  amp  cClusterIcon cluster  markers  length  gt  1        var markers   cClusterIcon cluster  markers       var a   360 0   markers length      for  var i 0  i  lt  markers length  i                  var pos   markers i  getPosition            var newLat   pos lat     - 00004   Math cos   a i    180   Math PI       x         var newLng   pos lng     - 00004   Math sin   a i    180   Math PI       Y         var finalLatLng   new google maps LatLng newLat newLng           markers i  setPosition finalLatLng           markers i  setMap cClusterIcon cluster  map              cClusterIcon hide        return            END MODIFICATION

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I like simple solutions so here s mine  Instead of modifying the lib  which would make it harder to mantain  you can simply watch the event like this  google maps event addListener mc   clusterclick   onClusterClick     then you can manage it on   function onClusterClick cluster       var ms   cluster getMarkers      i  ie  used bootstrap to show a panel with a list  which i find much more confortable and usable than spiderfying on  crowded  places   if you are using a clusterer chances are you will end up with collisions once you spiderfy   you can check the zoom there too   btw  i just found leaflet and it seems to work much better  the cluster AND spiderfy works very fluidly http   leaflet github io Leaflet markercluster example marker-clustering-realworld 10000 html and it s open-source

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Expanding on the answers given above  just ensure you set maxZoom option when initializing the map object

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For situations where there are multiple services in the same building you could offset the markers just a little   say by  001 degree   in a radius from the actual point  This should also produce a nice visual effect

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Adding to Matthew Fox s sneaky genius answer  I have added a small random offset to each lat and lng when setting the marker object   For example   new LatLng getLat   getMarkerOffset    getLng   getMarkerOffset      private static double getMarkerOffset          add tiny random offset to keep markers from dropping on top of themselves     double offset  Math random   4000      boolean isEven     int  offset  400000    2   0      if  isEven  return  offset      else        return -offset

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Expanding on Chaoley s answer  I implemented a function that  given a list of locations  objects with lng and lat properties  whose coordinates are exactly the same  moves them away from their original location a little bit  modifying objects in place   They then form a nice circle around the center point   I found that  for my latitude  52deg North   0 0003 degrees of circle radius work best  and that you have to make up for the difference between latitude and longitude degrees when converted to kilometres  You can find approximate conversions for your latitude here   var correctLocList   function  loclist        var lng radius   0 0003             degrees of longitude separation         lat to lng   111 23   71 7      lat to long proportion in Warsaw         angle   0 5                     starting angle  in radians         loclen   loclist length          step   2   Math PI   loclen          i          loc          lat radius   lng radius   lat to lng      for  i   0  i  lt  loclen    i            loc   loclist i           loc lng   loc lng    Math cos angle    lng radius           loc lat   loc lat    Math sin angle    lat radius           angle    step

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Offsetting the markers isn t a real solution if they re located in the same building  What you might want to do is modify the markerclusterer js like so    Add a prototype click method in the MarkerClusterer class  like so - we will override this later in the map initialize   function   MarkerClusterer prototype onClick   function          return true       In the ClusterIcon class  add the following code AFTER the clusterclick trigger      Trigger the clusterclick event  google maps event trigger markerClusterer   clusterclick   this cluster     var zoom   this map  getZoom    var maxZoom   markerClusterer getMaxZoom       if we have reached the maxZoom and there is more than 1 marker in this cluster    use our onClick method to popup a list of options if  zoom  gt   maxZoom  amp  amp  this cluster  markers  length  gt  1       return markerClusterer onClickZoom this      Then  in your initialize   function where you initialize the map and declare your MarkerClusterer object   markerCluster   new MarkerClusterer map  markers      onClickZoom OVERRIDE markerCluster onClickZoom   function     return multiChoice markerCluster       Where multiChoice   is YOUR  yet to be written  function to popup an InfoWindow with a list of options to select from  Note that the markerClusterer object is passed to your function  because you will need this to determine how many markers there are in that cluster  For example   function multiChoice mc         var cluster   mc clusters           if more than 1 point shares the same lat long         the size of the cluster array will be 1 AND         the number of markers in the cluster will be  gt  1         REMEMBER  maxZoom was already reached and we can t zoom in anymore      if  cluster length    1  amp  amp  cluster 0  markers  length  gt  1                   var markers   cluster 0  markers             for  var i 0  i  lt  markers length  i                                 you ll probably want to generate your list of options here                           return false               return true

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This is more of a stopgap  quick and dirty  solution similar to the one Matthew Fox suggests  this time using JavaScript   In JavaScript you can just offset the lat and long of all of your locations by adding a small random offset to both e g   myLocation i  Latitude     Math random     25000    I found that dividing by 25000 gives enough separation but doesn t move the marker significantly from the exact location e g  a specific address   This makes a reasonably good job of offsetting them from one another  but only after you ve zoomed in closely  When zoomed out  it still won t be clear that there are multiple options for the location

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Giving offset will make the markers faraway when the user zoom in to max  So i found a way to achieve that  this may not be a proper way but it worked very well      This code is in swift for loop markers     create marker let mapMarker   GMSMarker   mapMarker groundAnchor   CGPosition 0 5  0 5  mapMarker position     set the CLLocation   instead of setting marker icon set the iconView let image UIIMage   UIIMage init named  filename   let imageView UIImageView   UIImageView init frame rect 0 0    image width 2   markerIndex    image width   image height   imageView contentMode    Right imageView image   image mapMarker iconView   imageView mapMarker map   mapView     set the zIndex of the marker so that you will see the marker icon which you want to see on top  otherwise it will animate the markers like auto swapping  when the user tap the marker handle the zIndex to bring the marker on top using zIndex Swap

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Check this  https   github com plank MarkerClusterer  This is the MarkerCluster modified to have a infoWindow in a cluster marker  when you have several markers in the same position   You can see how it works here  http   culturedays ca en 2013-activities

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Take a look at OverlappingMarkerSpiderfier  There s a demo page  but they don t show markers which are exactly on the same spot  only some which are very close together     But a real life example with markers on the exact same spot can be seen on http   www ejw de ejw-vor-ort   scroll down for the map and click on a few markers to see the spider-effect    That seems to be the perfect solution for your problem

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Extending answers above  when you got joined strings  not added subtracted position  e g   37 12340-0 00069    convert your original lat longitude to floats  e g  using parseFloat    then add or subtract corrections

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How to get away with it    Swift       var clusterArray    String        var pinOffSet   Double   0     var pinLat   yourLat     var pinLong   yourLong     var location   pinLat   pinLong   A new marker is about to be created   check clusterArray and manipulate it s offset   if  clusterArray contains location            clusterArray append location        else            pinOffSet    1         let offWithIt   0 00025    reasonable offset with zoomLvl 14-16          switch pinOffSet           case 1   pinLong   pinLong   offWithIt   pinLat   pinLat   offWithIt         case 2   pinLong   pinLong   offWithIt   pinLat   pinLat - offWithIt         case 3   pinLong   pinLong - offWithIt   pinLat   pinLat - offWithIt         case 4   pinLong   pinLong - offWithIt   pinLat   pinLat   offWithIt         default   print 1                      result

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I used this alongside jQuery and it does the job   var map  var markers       var infoWindow   function initialize         var center   new google maps LatLng -29 6833300  152 9333300        var mapOptions             zoom  5          center  center          panControl  false          zoomControl  false          mapTypeControl  false          scaleControl  false          streetViewControl  false          overviewMapControl  false          mapTypeId  google maps MapTypeId ROADMAP               map   new google maps Map document getElementById  map-canvas    mapOptions          getJSON  jsonbackend php   function data            infoWindow   new google maps InfoWindow               each data  function key  val                if val  LATITUDE        amp  amp  val  LONGITUDE                                                         Set the coordonates of the new point                 var latLng   new google maps LatLng val  LATITUDE   val  LONGITUDE                        Check Markers array for duplicate position and offset a little                 if markers length    0                        for  i 0  i  lt  markers length  i                              var existingMarker   markers i                           var pos   existingMarker getPosition                            if  latLng equals pos                                 var a   360 0   markers length                              var newLat   pos lat     - 00004   Math cos   a i    180   Math PI      x                             var newLng   pos lng     - 00004   Math sin   a i    180   Math PI      Y                             var latLng   new google maps LatLng newLat newLng                                                                                         Initialize the new marker                 var marker   new google maps Marker  map  map  position  latLng  title  val  TITLE                          The HTML that is shown in the window of each item  when the icon it s clicked                  var html     lt div id  iwcontent  gt  lt h3 gt   val  TITLE     lt  h3 gt                      lt strong gt Address   lt  strong gt   val  ADDRESS        val  SUBURB        val  STATE        val  POSTCODE     lt br gt                      lt  div gt                        Binds the infoWindow to the point                 bindInfoWindow marker  map  infoWindow  html                       Add the marker to the array                 markers push marker                                         Make a cluster with the markers from the array         var markerCluster   new MarkerClusterer map  markers    zoomOnClick  true  maxZoom  15  gridSize  20                function markerOpen markerid        map setZoom 22       map panTo markers markerid  getPosition         google maps event trigger markers markerid   click        switchView  map       google maps event addDomListener window   load   initialize

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Adding to above answers but offering an alternative quick solution in php and wordpress  For this example I am storing the location field via ACF and looping through the posts to grab that data  I found that storing the lat   lng in an array and check the value of that array to see if the loop matches  we can then update the value within that array with the amount we want to shift our pips by    This is the value to shift the pips by  I found this worked best with markerClusterer  add to latlng   0 00003   while   query- gt have posts           query- gt the post         meta   get post meta get the ID     quot postcode quot   true     uses an acf field to store location      lat    meta  quot lat quot         lng    meta  quot lng quot         if in array  meta  quot lat quot    lat checker      check if this meta matches                    if matches then update the array to a new value  current value   shift value             This is using the lng value for a horizontal line of pips  use lat for vertical  or both for a diagonal         if isset  latlng storer  meta  quot lng quot                    latlng storer  meta  quot lng quot       latlng storer  meta  quot lng quot       add to latlng               lng    latlng storer  meta  quot lng quot               else                latlng storer  meta  quot lng quot       meta  quot lng quot                 lng    latlng storer  meta  quot lng quot                      else            lat checker      meta  quot lat quot      just for simple checking of data          latlng storer  meta  quot lat quot      floatval  meta  quot lat quot              latlng storer  meta  quot lng quot       floatval  meta  quot lng quot                 entry                quot lat quot    gt   lat           quot lng quot    gt   lng           Add all the other post data here and use this array for the pips             end query  Once I ve grabbed these locations I json encode the  entry variable and use that within my JS  let locations    lt   json encode  entry   gt    I know this is a rather specific situation but I hope this helps someone along the line

[javascript] Google maps API V3 - multiple markers on exact same spot

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