The Dutch coordinate system. What is RDNAP?


All countries have there own measurement system or even systems. In the Netherlands they use a system that’s called RD (Rijks Driehoek). it’s a network that consists of approximately 5600 RD points.
The location of RD get’s indicated from a church tower, a stone or a ground anchor.

X and Y coordinates

Every RD has an known X and Y coordinate. The X and Y coordinate give you the distance to 2 axes perpendicular to each other. There is one that goes from west till east (the Y axes), the other one goes from south till north (the X axes).
The Lieve Vrouwentoren that’s placed in Amersfoort, stands at a central point in the world of RD


If you want to compare heights within the Netherlands you have to use one zero point, that is were NAP steps in to the field. measuring height (altitude) can be crucial! It protects the Netherlands from floods for example. They use NAP to measure the height of there dykes and sand dunes. If they are not high enough they have to take action, otherwise the water could cause a flood.


To convert the coordinates of RD and NAP you have to use a transformation.
The RD and the NAP coordinate systems have been used for a very long time and there not going away anytime soon. This is because our whole cartography is measured with these systems. The same goes for other countries who have their own coordinate systems.

But most times a location is based on the data of GPS. While you are driving a car and you need simple navigation, it doesn’t matter that much if you are a little bit off. But when you are surveying you need to be accurate, and you want you location(s) to represent the coordinates of the country you’re in.

So in order to get all the measurements in the coordinate system of the country you are measuring in. the GPS or GNSS data needs to be transformed. Within the Netherlands it needs to be transformed to RD-NAP. There is only one way to transform the GPS coordinates to the RD-NAP coordinates, to do that you need RDNAPTRANS

RDNAPTRANS gets renewed on a regular base, that is because The continent of Europe is exactly moving. Because it moves with a few centimeters, coordinates also change. Currently RDNAPTRANS 2008 can be used until October 1st 2021. The newest instalment is called RDNAPTRANS 2018. It’s not yet clear when the newest transformation will take place, but until then you can use the 2018 version.

Finally, always make sure that you check the software you’ll be using. You need to check if the coordinate system you are surveying in is also available in the software you are using. The best way you can do this is by sending an email or calling the company you are going to purchase the software from.