Category: Navigation

All about maps, compasses, and finding your way

Mercator projections, a comparison


While writing the previous post on Rijksdriehoeksmeting and OziExplorer, we came upon two map projections: Oblique Stereographic and Transverse Mercator. In this post we will have a look at the Mercator and Transverse Mercator projections and try to compare. Both projections are quite frequently used. So let’s have a look at them.

Mercator projections are cylindrical projections. The earth, represented by a spheroid or ellipsoid, is projected on a cylindrical surface. In contrast to a sphere, a cylinder can be flattened out as a 2D surface, the map.

Spherical Mercator Projection

The page is supported by a Java code project MapDatumConvert on Github in which I have programmed the projections and Map Datum conversions between Rijksdriehoeksmeting and WGS84.

OziExplorer and Rijksdriehoeksmeting


OziExplorer is my favorite tool for working with topographical maps. Even in this era of mobile apps with all kind of online maps, I am a bit old fashioned by having my own collection of maps and OziExplorer is a great way to use them.

I am a Dutchy and here in the Netherlands the ‘authorities’ that are responsible for Dutch topographic maps use the Rijksdriehoeksmeting (RD) Map Datum.

Primary reference points of the Rijksdriehoeksmeting Stelsel

In this blog we look at the Dutch maps and describe how to get them properly working in OziExplorer.

Serving your own PDOK maps

I am fascinated by navigation and maps. When I visit a new location one of the first things I do is getting a topographical map of the region. Sometimes I use historical maps, like the Werbata map (dating from 1911, see also Wikipedia) for my trips to Curacao. Since 2007 I log my activities (like running, hiking, cycling, swimming, surveying) using GPS (TomTom watch) and I like to plot these on a map online. Since surroundings change, I like not only to have the most current maps, but also historical maps. As a Dutchy a found the Kabouterbond maps worthwhile. Since 2012 the PDOK Basisregistratie Topografie (BRT) maps which can be downloaded for free in raster or vector format. PDOK is a cooperation between het Kadaster and the Dutch government.

So I end up with a collection of digital maps which I like to use with OziExplorer (for route planning e.g.) and online on my own websites. This post describes the way I proceeded to serve my maps for online usage.

PDOK based vector map from my server, described in this post

OziExplorer maps from GeoTIFF


I still find Oziexplorer an excellent and versatile program for navigation, despite of the many, many apps relying on on-line maps.

This page describes how to create Oziexplorer maps from GeoTIFF, including map merge. As an example we take the Basis Registratie Topografie (BRT) Top25raster 1:25.000 maps of the Netherlands that can be downloaded from PDOK and we will create an ozfx4 map covering the entire Netherlands.

The GeoTIFF format is an image tif format that contains geo information.