Exporting MS Access databases to SQLite.

Posted by – Saturday 2015-07-25

Sometimes you are given a database in MS Access (MDB) format. If your operating system is MS Windows and you have a MS Access license, working with this database should not be a issue.

If your operating system is Linux, the odds of working smoothly with such database are not good. The usual recipe for opening a MS Accesss database – actually, a MDB file – in a Linux machine is using LibreOffice Base plus the appropriate database driver. While not a difficult task, finding the right database driver, installing it and, finally, configuring LibreOffice Base accordingly is usually a cumbersome, error prone and time consuming process.

MS Access to SQLite

The alternative explored in this post is exporting the database from MS Access to SQLite. Both database technologies have in common the feature of being serverless. The output of this export process is a SQLite database which, like a MS Access database, is stored in a single file.

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Some useful and aesthetic free map markers collections.

Posted by – 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 the marker icons usually provided by default might not be good enough. In this post we will list some collections of free map markers icons.

1. 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

2. 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 – 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 – 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 – 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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