Hunebedden (Dutch dolmens) in proportion
About orientation patterns with hunebedden (in European context)
The instruments used
NB. On the page Measurement of ground plans phase numbers are provided with the measurements.
This number matches the phases below.
Measurement phase I: Measuring with a normal compass
This website started off with the observation, that a few hunebedden stand orientated towards each other.
This first observation and later on also some in the Ardèche were done sec with a comass.
They aren’t of any value for further investigation, but still worth mentionening since they determined the course of this study.
From these observation it became clear, (1) that the orientation of hunebedden and dolmens was constructed and
(2) that there seemed to be no relation to the latitude.
Therefore from the beginning the orientation lines in a hunebed were treated as a composition of angles
This approach also reduced the divergence between those lines.
Measurement phase II: Measuring with a hairline-anglemeter
In order to be able to posit ideas about orientation petterns, a more exact instrument was needed.
A handmade ’hairline-anglemeter’ with two hairlines at 20 cm of each other and a compass attached,
appeared to be a good solution. With a test arrangement it had an accuracy of 0.5° when measuring to and from.
The instrument was placed levelly, after which it should be calibrated via a combination of azimuth and initial angle.
Subsequently the mutual angles between the lines, which linked the outstanding points in a hunebed, were measured.
This method has lead to the observation, that hunebedden contain markings most of the time.
But the levelling and calibration took quite a lot of time.
Measuring phase III: Measuring with a handheld sounding compass and a tape line
After some time it became desirable to compare patterns with ground plans.
Using the hairline-anglemeter this got bogged down in a very time consuming activity. A new instrument was needed: the Recta DP10.
This is a sounding compass with an exactness of one third of a degree when measuring to and from.
The reading mechanism levels itself automatically. Reading is done through a prism via a hairline, which must be pointed at the object.
The first ground plans were produced by means of the sounding compass and a tape line.
Measuring phase IV: Measuring with a laser distancemeter and a digital anglemeter
New technics allow even more accurate measurements.
At this moment a combination of two digital meters is used:
a digital anglemeter (fault ±0.1°) and a laser distancemeter (fault ±0.5mm).
The distancemeter is equiped with a intern inclinationmeter and calculates the horizontal distance automatically.
The measurements are stored via a program on a pda, which creates a ground plan of it right away.
Mistakes directly catch the eye and can be corrected on the spot.
By remeasuring the same measurement points, this method showed to have a erronous placing of maxiamal one centimeter under normal conditions
and of ample one centimeter with bad terrain conditions.
Beforehand the program asks for the going magnetical deviation and it adapts the measurements automatically to this.
Level differences are displayed in darker and brighter lines.
Operating procedure: Using a laser waterlevel (fault ±0.4 mm/m) all measurement points get a sticker.
The sounding compass (fault ±0.3°) is used to initialize the computer program via a reference angle and the accompanying azimuth.
Next the measurement points are stored in the program as a combination of distance and angle.
This results in a horizontal crosscut of the monument at 10 till 30 cm above the ground.