web-mercator-projection

Web Mercator Projection

A Go project to explore the Math to calculate and present data in a map using the Web Mercator Projection.

To get more information about this topic, please look at the following references:

• https://en.wikipedia.org/wiki/Web_Mercator_projection
• https://www.maptiler.com/google-maps-coordinates-tile-bounds-projection/#3/15.00/50.00
• https://wiki.openstreetmap.org/wiki/Slippy_map_tilenames

How does this project work?

In the main example project, there is a file main.go that contains the following actions available:

• Convert a LonLat into a Point coordinates and vice versa.

• A function to add a Red-Marker into a map image. (The coordinates must be setted manually in the code)

  The resultant image will be stored in a folder named data.

This is how the main.go will print out the information:

LonLat: {-74.92010258781309 11.045882360336755}
Point: {298.8939304168872 480.38414652354516 2}
Tile: {1 1 2}
LonLat from Point: {-74.9201025878131 11.045882360336744}

Structs definitions

• LonLat: A location in the map using angles in degrees.
• Point: A pixel in the map for a specific zoom or scale.
• Tile: Represent at which (tile/block) a Point or LonLat is.

If you are curious about how the maps where built using the data in OpenStreetMap please take a look at this Gist https://gist.github.com/jorelosorio/7042bd27e4b2bb03865215d6a5607266

Tools

• GoLang 1.17
• Docker
• ImageMagick 6.9.11-60
• Visual Studio Code Optional!

  It requires a Remote - Containers extension. for more information please refers to: https://code.visualstudio.com/docs/remote/containers#_getting-started

Development

This project contains a Dockerfile file with all required dependencies to run it using Visual Studio Code + Remote - Containers extension. However, if you want to make it run locally in your development machine, please follow the instructions below.

Install Go

Install it from https://go.dev/dl/

Install ImageMagick

Install it using the following instructions https://imagemagick.org/script/download.php

Build the executable

go build ./examples/main.go

The binary file depends on the assets folder to build the map, make sure to have it on the same directory.

Licences and assets

• OpenStreetMap data is licenced under the Open Data Commons Open Database Licence (ODbL). https://opendatacommons.org/licenses/odbl/1-0/

• Red marker icon https://www.iconfinder.com/icons/299087/marker_map_icon Creative Commons (Attribution 3.0 Unported) http://creativecommons.org/licenses/by/3.0/