When I go to OpenFietsMap.nl, it looks like the RD-coordinates are a bit off. I compared them to the maps from PDOK.nl. This website distributes topographic maps of the Netherlands for free.
Example:
I looked at the coordinates at waypoint 71 in Alkmaar (permalink to the map). When I hover my mouse above the waypoint, in the bottom of my screen it says RD (111423.42935,518026.83679). My interpretation is that this means X 111 423 Y 518 027 when rounded off.
When I get out my map (source: PDOK.nl, it’s the 1 : 25 000 map of the area), the coordinates I measure are X 111 444 Y 518 145. So that’s about 120 metres away from what I see on OpenFietsKaart.nl.
Back on OpenFietsKaart.nl, next to the RD-coordinates, it says Lon: 4.74365 Lat: 52.64908. This looks like the universal coordinate system, only with latitude and longitude in reversed order. When I put these coordinates into the converter at gpscoordinaten.nl I get 111447, 518143 as RD-coordinates. These confirm the coordinates I measured on the PDOK map.
120 metres is a relatively small error so you don’t immediately see that something is going wrong. That’s a problem, because when communicating coordinates you end up at a different place than intended without knowing that there is an error.
To me it looks like there is something going wrong with the coordinate conversion at OpenFietsKaart.nl. Where can I report this issue? The wiki directed me to this forum, so that’s why I’m posting here.