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Editorial Team
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Asked: 2026-06-04T23:14:26+00:00

I am currently building a Google Maps project that will dynamically load and unload

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I am currently building a Google Maps project that will dynamically load and unload various KMZ files based on user input. It works fine for roughly 8 layer loads/unloads, but then Google Maps breaks down with the 414 error. I’ve traced the problem down to the stored string the API is generating to refer to each KML layer.

Here’s the code that runs when a layer is clicked:

function showLayer(layername) {
  if (layers[layername].kml === undefined) {
    layers[layername].kml = loadKML(layers[layername].file, layers[layername].options);
  }
  layers[layername].kml.setMap(map);
  redrawRoutes(layers[layername].kml);
}

And the loadKML function:

function loadKML(file, options) {
  var path = kmlDir + file;
  options = options || { preserveViewport: true };
  layer = new google.maps.KmlLayer(path, options);
  return layer;
}

Basically my goal is to only load each KML file once, store it in an object, and just reference that on subsequent loads/unloads. The problem here is that inside the Javascript Object that new google.maps.KmlLayer generates, a big long string

"kml:cj5TNh3iqySpI_DAGiDgbSJESQ-dakZTiMY09US6imjvFNPMTIIYNAg|ks:;dc:cg;ts:44610546|kv:3|api:3"

and appends this to the request URI each time. This adds up rather quickly, and after 7-8 appends the URI is too long and any subsequent requests are ignored.

Is there a way around using this long request string, can I force it to use a custom string, or just clear the URI each time? I will only be dealing with ~6 total files, and I’d really like to be able to handle as many layer loads/unloads as possible.

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1 Answer

  1. Editorial Team

    You are trying to optimize what Google already has. Google cache’s KML files and their associated tiles so there is very little penalty for destroying and recreating layers. As long as the url to the KML layer stays constant, you should just destroy then recreate the layer.

    Regardless of the number of KML files currently on the map, Google renders them as a single tile overlay. Your users have to download new tile images everytime you add/remove KML layers via setMap.

    Your KML file will only be accessed once every few hours. Supposedly, Google attempts to honor the cache headers issued for the request to the KML file. However, it’s not specifically defined how long Google will cache your KML when strong cache headers are missing.

    Google also imposes minimum caching times so that even if you were to specify via strong cache headers that your KML file should expire after 1 minute, Google would still cache the file for it’s preset (and undisclosed) time. The standard workaround is to add extra querystring parameters to the KML url in order to generate a new/unique address that hasn’t been previously cached.

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