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APPENDIX II
APPENDIX II
RADIOMETRIC LEVELLING
This must be done in the laboratory by mounting the instrument on a stand
that can be rotated around an axis that is accurately vertical and passes
through the centre of the receiving surface. The instrument then is illuminated
by a lamp so that radiation falls at an elevation of approximately 15° to the
horizontal; the lamp should be fed by a constant voltage supply.
The output from the radiation instrument is measured at various azimuths and
the level of the instrument adjusted independently of that of the rotating stand
until the least possible variation is obtained as the instrument is rotated
around the vertical axis. Once this has been done, the spirit level is marked so
that the correct level can be found back outdoors.
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