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National Technical University of Athens
School of Civil Engineering
Department of Water Resources and Environmental Engineering

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Collection of technical software-development-related writings.

Introduction to geographical co-ordinate systems
In this concise introduction, I explain essential things you need to know when working with geographical co-ordinate systems. I explain why many geographical co-ordinate systems are being used and how to use the free Proj software to convert between them, and I make recommendations on how to store co-ordinates in your database. I assume you already know what latitude and longitude means and what cartesian (x-y) co-ordinates are, and that you have some understanding of the geometrical term "projection", notably what we mean by "project a 3d shape to a plane". The last section is intended for programmers.