Author:

Diego Alberto Arias Prado

Some useful and aesthetic free map markers collections

Posted by Diego Alberto Arias Prado – Tuesday 2013-01-22

When creating a web map with OpenLayers, Leaflet, Google Maps or similar, a problem that sometimes arises is finding useful and aesthetic map markers, especially when it is required that the markers themselves have a meaning – for instance, points of interest – that is inmediate to users.

Under this requirement, usually the marker icons provided by default are not enough. In this post we will list some collections of free map markers icons.

Google Maps icons, and more.

A set of map marker icons intended to be used to represent points of interest can be found at http://www.lass.it/Web/viewer.aspx?id=4.

Google Maps map markers

OpenStreetMap map icons

The Open Street Map project has its own set of map icons, that can be found at http://wiki.openstreetmap.org/wiki/Osmarender/Symbols.

Open Street Map icons

The Open Street Map icons themselves can be found at the Subversion repository http://svn.openstreetmap.org/applications/share/map-icons/svg/, which is accessible via a web browser.

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OpenLayers cluster strategy active state depending of current map scale

Posted by Diego Alberto Arias Prado – Monday 2013-01-07

1. The arena.

Among the strategies that OpenLayers has, a very important one is the cluster strategy (class OpenLayers.Strategy.Cluster). As explained in a OpenGeo workshop about OpenLayers [1]:

Loosely speaking, the OpenLayers.Strategy classes tie together the layer and the protocol. Strategies deal with when to make requests for data (or when to send modifications). Strategies can also determine how to prepare features before they end up in a layer.

The cluster strategy will pack together near features in a single one (clustering) before they are sent to the vector layer and rendered. The clustering threshold can be set by pixels or by distance.

OpenLayers cluster strategy example

This strategy is very useful when we have to deal with the task of showing a layer with a large number of features and we want offer users a clear presentation. Typically, this problem will happen at low zoom levels or, equivalently, at high map scale values. In this situation, most of the features, if not all, will lie in the map extent corresponding to the viewport.

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Apple’s pinch-to-zoom patent, rejected in the USA

Posted by Diego Alberto Arias Prado – Thursday 2012-12-20

A new slap in the face of Apple, the company that some years ago introduced itself as “… shameless about stealing great ideas“. The US Patent Office has rejected its pinch-to-zoom technology patent claims:

Via MercuryNews.com:

The U.S. Patent and Trademark Office has taken a second look at Apple’s (AAPL) pinch-to-zoom technology and this time found it wanting.

In a letter sent to Apple’s lawyers on Wednesday, the office said it has completed a re-examination of the iPhone maker’s patent on its zooming technology and has rejected all of Apple’s claims. Citing older patents and published documents, the patent office found that Apple’s claimed innovations were “unpatentable.”

link: http://goo.gl/gzycT

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Beware of decimal pixel values in OpenLayers

Posted by Diego Alberto Arias Prado – Wednesday 2012-12-19

So you are programming an OpenLayers based map viewer and attempt to make a WMS GetFeatureInfo request, whose response will later be pretty-formatted and shown to the user. To accomplish it you create JavaScript code like the following: 

var parameters = {
    srs: map.getProjection(),
    bbox: map.getExtent().toBBOX(6),
    width: map.getSize().w,
    height: map.getSize().h,
    x: evt.xy.x,
    y: evt.xy.y,
    layers: 'municipalities',
    query_layers: 'municipalities'
};

OpenLayers.Request.issue({
    method: 'get',
    url: this.getFeatureInfoUrl,
    async: false,
    params: parameters,
    success: function(data) {
       var responseText = data.responseText;
       // ...
    }
});

where evt (lines 6 and 7) represents the mouse click event that triggered the GetFeatureInfo request.

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Apple Maps (and user irresponsability) can be deadly!

Posted by Diego Alberto Arias Prado – Thursday 2012-12-13

It happened near of Mildura, a regional city in the southeast of Australia with hot, semiarid climate. Police officers had to rescue several car drivers who got lost in the middle of nowhere without water, food or even cellphone reception while suffering temperaures as high as 46 Celsius (~115 Fahrenheit) degrees. All these car drivers had in common that they wanted to arrive to this city, they followed the indications given by the Apple Maps application and they got lost in the middle of nowhere.

Mildura on Apple Maps
In this picture, created by the Mildura police, the purple pin shows the actual location of the town and the red one the wrong given by Apple Maps.

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