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Technical Overview: GeoNames

Apr

5

2010

GeoNames is a series of web services to an extensive geographical database of over 8,000,000 names. The database is also available for “bulk” download. Both access methods are under the Creative Commons attribution license. The web services are available through free and commercial interfaces, and using a number of different format/protocols.

Polar Maps and Projections: Part 2, Implementation

Jan

18

2010

The first part of this article looked at different ways of producing polar maps and surveyed a number of different azimuthal projections that are often used for polar maps. In this second part, I produce a working implementation using UMN MapServer and OpenLayers.

Polar Maps and Projections: Part 1, Overview

Jan

11

2010

With the success of my earlier series on global equal area map projections (starting with this overview), I received a number of requests to produce a similar how-to article for polar maps. The first part of this article (published here) provides an overview of a number of different map projections commonly used for polar maps. ...

How to create an online map with a non-Mercator Projection: Part 2

Sep

23

2009

In the first part of this article we created a WMS server of basemaps using an unconventional map projection (the Mollweide projection). In this second part, we shall implement the client side of the project, creating a working application that will plot user data on the basemaps.

How to create an online map with a non-Mercator Projection: Part 1

Sep

21

2009

Previous articles in this series, discussed different coordinate systems and map projections available, and why different systems suit different applications (Part 1, 2). This was followed by a look at geostatistical and thematic maps where data areas and data densities are important (Part 1, 2, 3). Virtually all online map applications use the Mercator projection. ...

Choosing a Projection, Part 3: Pseudo-Cylindrical Projections

Sep

16

2009

After looking at the need for global equal area projections and a number of different possible projections, we shall now look at the pseudo-cylindrical options. There are a lot more of these, so we cover them in an article of their own. Pseudo-cylindrical projections are similar to cylindrical projections, but the central meridian is the ...

Choosing a Projection, Part 2: Pseudo-Conic, Azimuthal, and Cylindrical Projections

Sep

15

2009

In the first part of this article, I argued against the use of Mercator and Equirectangular projections for web maps showing global data distributions and areas. Instead, an equal area projection is more appropriate because it preserves relative areas and data densities. In the final two parts, I shall look at some possible equal area ...

Choosing a Map Projection: Part 1

Sep

14

2009

Previously in this series (1, 2), we discussed the different map projections and coordinate systems that can be used for map generation. We also looked at the reasons for the many different projections, and some of the reasons why we might wish to choose a different projection. In this article, I shall make the case ...

Map Projections and Coordinate Systems: Part 2

Sep

9

2009

In the second part of this article, I shall look at map datums and coordinate systems. In the first half, published on Monday, I looked at different projection systems. As we saw in the first part, the map projection converts the curved surface of the Earth into a flat map. The datum is the model ...

Map Projections and Coordinate Systems: Part 1

Sep

7

2009

This two part article is intended as an introduction to map projections and coordinate systems. The second part of the article will be published on Wednesday. They start a new series of articles which I shall be publishing over the next few weeks. I shall look at different projections and coordinate systems, the inadequacies of ...