Map-drawing directly on aluminium-paper-foils with re
production by photolito or drawing on plastic sheets with
gum-bichromate-printing on lithoplates (« direct-printing »)
13. Map-editing and reproduction
Survey Board however, they are testing the standards used, as part of
the drawing up of a new surveying ordinance. To reach this precision a
suitable negative scale must be chosen. Further the point error as a func-
tion of the negative scale, must be known. Precisiontests with the air-
camera Zeiss RMK 20, 30 x 30 and signalled points showed an average
difference between map-coordinates and geodetically determined coor-
dinates, Dk = 3,5 x N cm where the negative scale = 1:1000 N, and
the same value for the heights.
By fitting the stereomodel on the pass-points the divergence may
not exceed + 0,3 mm on the map and 0,3 m in the height.
The geodetic net-work usually consists of traverses. For urban maps
the maximum angle-closing-error allowed 0°,02\/ ^» where n is the
number of angles measured, and the maximum pointclosing-error
allowed for the endpoint of the traverse — 0,00035 L + 0,06 meters,
where L is the length in meters of all sides together of the traverse. For
Legal Change and Re-allotment maps the corresponding error-limits
are 0,04y » and 0,00070 L + 0,12 meters.
Signalling of -passpoints and certain boundary marks is usually
made with boards of wood fibre. The dimensions of these are decided for
different cameras and negative scales from nomograms.
Photointerpretation on the field is made for built-up-acreas and in-
fields. For wooded ground and outlaying land investigations are made,
to replace photointerpretation on the field partly or alltogether by pho-
tointerpretation in the office.
Stereoplotting is made in a Wild A 5 and an A 6. The maps are con-
sequently all drawn.
2. Other topographic maps for various purposes.
a) Maps for projects of public works.
I. The Order division of the Geographical Survey Office has compiled
maps for projecting of dams and of damages in connection with this.
Scales of the maps: 1:10 000, 1:4000, 1:2000 with the negative scales
1:20 000, 1:10 000 and 1:5000 respectively. Contour-intervals 5, 2 and
1 meter. Surveying camera: Zeiss RMK 20,30 30. Plotting instruments:
Stereoplanigraph, Wild A 5 and A 6.
The geodetic net-work consisted of a sparse triangulation or of in-
dependent chained stretches. A photogrammetric triangulation, «mo-
deltriangulation » is made in precisionstereoplotters and coordinates are
determined for a number of signalled net-points.
Fieldwork: Before taking the airphotographs passpoints, basepoints,
photogrammetrical fix points, certain boundary marks and parts of the
damming line were signalled. After taking the photographs at least 5
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