54
waarde valt binnen de waarnemingsnauwkeurigheid bij het af-
standmeten. Ook de B-, C- en D-kristallen vertoonden onbeteke
nende afwijkingen.
Litteratuur
CARTOGRAFIE
D. DE GROOT,
Een raamkaart is een kaart, begrensd door rechte lijnen, zoals
bijv. een stafkaart; de kadastrale kaart is een eilandenkaart.
Er zijn verschillende motieven om de raamkaart bij het kadaster
in te voeren, zoals eenvormige administratie, betere publiciteit,
logische aansluiting; de toepassing van moderne methoden van
samenstelling (fotogrammetrie) en reproduktie wordt eenvoudiger;
een beter aansluiting wordt verkregen met stadskaarten. Een nadeel
is de onvermijdelijke versnijding van percelen.
1. J. Kelsey, Empire Survey Review, 15, nr. 112 (1959), 58-65.
2. T. L. Wadley, Empire Survey Review, 14, nr. 106 (1958), 152.
3. A. L. Allan, Commonwealth Survey Officers' Conference 1959, paper
no. 28, p. 2.
4. J. Kelsey, Commonwealth Survey Officers' Conference 1959, paper
no. 26, p. 28.
Some remarks on the. use of the TellurometerAfter a brief description
of the basic equipment, a number of properties of the transmitted micro
wave-beam is described with reference to the orientation of the instruments,
the visibility between observers, reflections causing ground swing and
meteorological effects on velocity. Zero errors as well as instrumental and
velocity inaccuracies are dealt with. In order to find out the zero error,
test measurements were made on the international calibration base (Loener-
mark). The error was estimated at 2 or 3 cm. Sometimes considerable
swing (up to 11 mfis) occurred at distances of 288 m and 576 m with in
struments at tripod height. The ground surface was covered with heather
and young fir-trees of about 3 ft high. At a distance of 35 m the measuring
line ran parallel to a series of concrete pillars; a small hill causing them to be
in its electrical shade during the measurements. The swing could not be
explained by an excess length path. No improvement was stated when
experimenting with a 5 ft high vertical metal screen erected at an oblique
angle halfway between both instruments in order to eliminate any ground
effects. In the recently reclaimed Yssel-lake polder covered with reed and
other marsh vegetation third-order traverses with side-lengths of a few
kilometers proved to be extremely useful, with closing errors of about
4- 15 to 50 cm over a total length of approximately 25 km. In the
Surveying Department of the Ministry of Public Works the present author
had a considerable practical experience with the tellurometer in providing
third and lower order fotogrammetric control. The mean side-lengths of
traverses were above 500 m, and an average adjustment had to be made of
less than 1 cm per 100 meters. After a nine months' use of the telluro
meter a crystal-calibration was made in which the A crystal proved to be
only 4 c/sec off. Also the B, C and D crystals gave insignificant deviations.
hoofd van het bureau voor Buitengewoon Landmeetkundig werk te Utrecht:
De raamkaart bij het kadaster
