The benchmark game in the Netherlands
by Prof. Y. Lupardi

made by Piet Vogelaar
.

Basics

In the Netherlands we have about 5500 measured points in the official list of the Kadaster. There are different groeps:

  1. Churches (Roman Katholic or Dutch Reformed mostly) that were used in the old days for triangulation. The top of the tower you can see from afar and they are reasonable stable compared to the accuracy of the instruments in those good old days. In this group you also have modern tall and stable buildings. Watertowers are a favourite for being strong, sturdy and well supported. And also for having a long lifestan compared to modern urban and industrial towers (chimneys).
  2. The special markers from the RD KernNet Network, being part of a European-wide geodetic network. These bald bronze nails (head diameter 25 mm with a 1 mm position hole) are set into concrete and their position is given in millimeters. Also the height (NAP) is known within a few millimeter. They all have a good view all around for use of GPS systems and are easily accessible by car.
  3. Next are the normal markers, mostly fixed on big concrete infrastructures like bridges or other big man-made structures (monuments). These also have a long filespan and are fixed to the deep underground. These are criteria from having chosen them. Sometimes you have a good line of sight to nearby towers or - more likely for new markers - a good GPS signal reception.
  4. De NAP (Normaal Amsterdams Peil) markers have no exact position. Mostly they are placed in walls of buidings of long standing and are mostly a long way from open water.
  5. Markers used for airial photography. Mostly placed on roads (bicycle paths are a favourite) they are like eyes looking to the sky. Theu have a round white centre surrounded by a black ring of paint. Mostly, but not always, there is a small metal pin in the centre. If you see one, you see the other one in most cases. With these known points clearly visible on the resulting pictures, these can be calibrated in stereoscopic view for use in the construction of maps.
  6. All other markers that are or were in use by a private firm for some project. They are mostly simple nails, the big ones with the text 'Meet-Punt' or 'Mess-Punkt' on it; the small ones come only with a crossmarking.
    meetbouten
    Here is a picture I made of new ones of the format 25 mm head and 50 mm pin and text 'MEET PUNT' on it together with my GPS12. They are sturdy rost-free steel nails but you cannot hammer them into concrete. So be not surprised when you find a disproportionate number of them in tarred (asphalt) bicyclepaths.

The game

To get an idea of what we in the Netherlands are doing, you can take a good look at what happens at this site. Since november 2004 there is a hunt going on: find a marker, make photographs, log your visit and tell stories. The pictures are organised in a photoalbum. See here: MEETPUNTEN FOTO ALBUM. More info about our benchmarks and downloadable lists with positions can be found her: RD Meetpunten jacht (Engels: Benchmark hunting) .

back