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Measurement plan at western passage of Knowth

Measuring the azimuth

• It would be great to have already a good survey of the site (inside and outside), at the proper scale
• Can we have a pre-visit Knowth (on Friday 15/9/00 and Thrusday 21/9/00) to get a better impression and discuss/measure certain matters (like the trees/buildings in front the passages). Look for locations that can be used to measure the direction of the passages (by GPS and compass).
• The main thing to determine is the azimuth of the western passage. At this moment (using the literature), the azimuth of Knowth west could be between 262° and 264° and the apparent altitude between 0°  and 1°.


Here one sees the measurements to be done with a laser from within the passage (at the bent in the passage). The following points are important:
1. A: the max. northern azimuth of the passage
2. B: the max. southern azimuth of the passage
3. O: Combining A and B gives O (the average azimuth of the passage and could be in the direction of Fennor)  (to be marked by GPS)
4. AA: the northern shadow the gnomon makes in the passage
5. BB: the southern shadow the gnomon makes in the passage
6. X: middle of the passage entrance (to be marked by GPS)
7. Beside these measurements also the altitude direction of the western passage will be determine (as well as the horizon level).
To do these measurement, three people will be welcome: one to hold the laser in the passage, one just outside the passage to convey messages with the third person, who has to mark the points as far as possible away from the passage.
This will take some two hours (incl. preparations). For this one needs access to the western passage.

If the direction O-X is through the trees, we have a problem (perhaps solvable, we will see)...

When we have these points, one person will travel by car (incl. a GSM) towards Fennor (or any other place needed).
Another person looks through the telescope over the middle of the passage entrance (X) and point O towards 'Fennor' (or any other place). By means of GSM we hope to find each other somewhere in space;-). If the car is along the line X - O, then this will be marked with the GPS.
For this we don't need to be in the passage (perhaps only being above the passage). This will take another 2 hours.

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