graphic Map 1:25000. Thus, this method of projecting saves the special preparation of rectified
aerial photographs simultaneously converted to 1:25 000 scale.
nside-
ilable, When the planimetric accuracy of the map 1:25 000 shall be maintained, this simple method |
is very limited by the differences of elevation in the terrain. The same restrictions also apply to if s
simple rectifications which are placed below a plastic foil of the map to be revised. il
With dynamic terrain, instead of such sim- |
rn ple rectifications, orthophotos are used to an increa-
sing extent for the revision of the Topographical 1 Photo flight at 1:30000 scale
———À Map 1:25000 [4] (fig. 2). The aerial photographs
are taken especially for this purpose, at 1:30 000
| scale and with 60 % longitudinal overlap. The or- 2 Simple enlargement to 1:10000 of the
eal thophotos are prepared at 1:10 000 scale. The ex- corresponding aerial photographs
penses for the preparation of the 8 orthophotos
io for one sheet of the Topographical Map 1:25 000 :
ing amount to about 3,500. -- to 4,500. -- DM. Field 3 Field checking onthe enlarged aerial photographs
to- reconnaissance is made before the revision ma- Bd corp with thé map 1. 25000 to oc I
nuscript is prepared. It is performed on simple
enlargements 1:10 000 ofthe original aerial photo-
— graphs and is essentially limited to changes in
road classification and to such topographic featu-
res, which are not unequivocally identifiable on
the aerial photograph. After field reconnaissance |
500 which takes on the averezs 5 days only for about Reduction to 1:25000 of the four plastic sheets IE
125 km2, the corrections are directly taken over 5 1:10 000-and combination. into one map sheet JI
4 Drawing in blue of new parts at 1: 10000 scale I
in sheet quarters on astralon |
c as final drawing in accordance with the enlarged
— key to symbol. An enlarged diazo print 1:10 000
(quadrangle) is superposed onthe orthophoto on 9 Photographic combination of the new drawings
he light table. When transferring the modifications 6 and lettering on the plastic revision sheet 1:25 000,
Aap on the diazo print, it is advantageous to use rub- after having photographically eliminated the out-
bing or pressing down plastic foils, i. e. that it is dated elements Fig. 2
me not necessary to draw many new symbols but that
these can be transferred to the corresponding Revision of the Topographic Map 1: 25 000
places on the map to be revised by simple rubbing According to Orthophotos
or pressing down of sample plastic foils.
- The preparation of orthophotos is considerably expensive. If orthophotos shall be prepared
ision for the only purpose of revising the Topographical Map 1:25 000, this procedure is only economic,
field as to my opinion, when extensive corrections are necessary. But in case such orthophotos are pre-
e pared for other purposes, they will constitute a very suitable means and are highly welcomed for
| Fig. | the revision.
ins of the 6.3. Revision Predominantly Based on Stereo Plotting Ï
ipt In order to maintain the planimetric accuracy of the map 1:25 000, the aerial photographs
should berestituted stereoscopically already in a hilly terrain, in case one cannot or does not want
to prepare orthophotos. For such a restitution of aerial photographs there are various instruments
available. For the revision of the Topographical Map 1:25 000 only those instruments have proved
maps suitable for our purposes, which guarantee a certain accuracy and admit the "photo-on-map tech-
photo- nique", i.e. an internal restitution and a direct comparison between stereo model and the map to
son be revised.
With the Double Projector DP 1 of Messrs. Zeiss, Oberkochen, the model is produced as
an anaglyph and can be projected directly upon the map. For wide-angle photographs this instrument
is. has a range of magnification of 2.5, 2.0 and 1. 6 times. By means of this instrument very good
e re- results have been obtained. From aerial photographs at 1:25 000 scale the model is projected upon
nt aerial enlargements 1:10 000 of the Topographical Map 1:25 000. Fainted diazo prints of the map image on
phs at dimensionally stable white cardboard have proved to be suitable as support. Blue copies have not
)0 photo- been suitable for plotting, as the anaglyph is sufficiently identifiable. By the preparatory work done
Topo- with the DP 1, the subsequent field work could essentially be reduced. The mixed image produced
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