Difference between marker and POI

Hi all,

I am new to OSM and currently develloping an interactive map. The map itself is no problem so far.

I read what I found but it wasnt quite clear to me.

  1. When do I use Markers and what are POI then?

  2. When I add divs after the “basicMap” (from the examples), they disappear under the tiles. Why - and how can I prevent that?

  • ok, a z-index of 750 does the trick. 575 does not. ist there aan exact value?
  1. When I want to store POI or Markers inside a Database - how do I access them?

    var pois = new OpenLayers.Layer.Text( "My Points",
                    { location:"./textfile.txt",
                      projection: map.displayProjection

  1. I forgot number 4 :slight_smile:

I really really like that map and all its features! I just spent three hours editing my neighbourhood :slight_smile:

Best regards,


I remembered #4:

If I collect 2000 POIs and parse them into my layer - how can I load only those located within the viewable map? Does the api load and unload them automatically?

  1. Markers are just a representation for any location on the map, which can include points of interest (POI), depending on which points you are interested in displaying.

  2. The markers may be retrieved from a database with a PHP script for example: location:“mypois.php”, or location:“http://www.example.com/mypois.php” . The PHP script would retrieve from the database and create a type text/plain (or is it plain/text?) response.

  3. You may load all POIs at once, limited only by the browser’s ability to handle them all. The API will show and hide them as the display view changes.

Hey Mike

great! Thank you a lot. I try and contact wheelmap.org because they have quite an nice GUI for openlayers.

  1. does the plain/text need to contain tabs? Is there a way to switch to ann array or such?

The plain/text file format can be several types (CSV, XML / JSON, I think). I believe it must be formatted and cannot just be a PHP array, but there should be PHP resources to convert to a defined format.

So I dont need to tell openlayers what the separator character is, right? It takes tab, ; and xml or json and decides itself.

Oops, I see that it is tab-separated only : http://dev.openlayers.org/releases/OpenLayers-2.10/doc/apidocs/files/OpenLayers/Layer/Text-js.html

Well - I guess it has some reason or it need to be changed :slight_smile: