4.5. Accuracy
The accuracy of the situation on the large-scale
topographic map meets the following requirements:
(i) The error in the location of the situation elements in
respect to the near geodetic points should not exceed
+ 0.4 mm.
(i) The distances between clearly depicted objects and
borders of the terrain (buildings, railways, roads and
structures, iron and concrete columns, etc.) located at
a distance of up to 150 m, measured from the map
and on the terrain should not differ by more than 0.6
mm;
(ii) For the other situation details these differences
should not exceed + 1 mm.
The accuracy of the contours meets the following
requirements:
(i) In open (unforested) regions the differencesbetween
the altitudes measured on the terrainand those,
obtained by interpolation between thecontours, should
not exceed:
for the scale of 1:10 000 +(1+4tg« ),
for the scale of 1:5000 + (0.8 - 3.5 tg. ),
for the scale of 1:2000 + (0.5 +2tgX ),
where À is the terrain slope angle near the check point.
(ii) For forest regions of an area up to 1 sq. km
irrespective of the height of the trees, and for forest
regions of trees height of up to 4 m irrespective of the
area, the accuracy of the relief depicted on the map is
as in the previous item (i);
(iii ) In forest regions with trees height of more than 4 m
the required accuracy is lower.
5. REVISION OF THE LARGE-SCALE
TOPOGRAPHIC MAP
Only map at scale of 1:10 000 and 1:5000 in coordinate
system, sheet division and nomenclature as in 4.2 above
are revised. For this purpose mainly photogrammetric
methods (analogue stereoplotting and orthophotoscopy)
and in rare cases survey methods (electronic
tacheometry) are used.
Survey methods for map revision are applied in the cases
when the changes in the map content are relatively small,
when the map content is scarce in situation details or
when it is impossible to take the aerial photographs. The
photogrammetric methods for revision of the topographic
map are applied when the changes in the situation are
more than 2096 and the situation content is very rich.
The revision of the large-scale topographic map is done
every 4-5 years for the intensive regions of the country
and every 8-10 years for the other regions (Instruction,
1985).
440
6. PHOTOGRAMMETRY
6.1. The Beginning
Bulgaria was probably the first country on the Balkan
Peninsula to begin to apply photogrammetry. Terrestrial
photographs were taken during 1907-1908 and were
plotted in the Vienna Cartographic Institute by Eduard
von Orel by means of a Stereoautograph designed by
him. During the Balkan War (1912) and the World War |
(1914-1918) aerial and terrestrial photographs were
taken for military reconnaissance and road construction,
More considerable attempt to apply terrestrial
photogrammetry for compilation of a topographic map at
scale of 1:25 000 was done in 1928. For the same
purpose in 1930 began the implementation of single-
frame aerial photogrammetry and in 1940 - of aerial
stereophotogrammetry. For large-scale mapping single-
image photogrammetry was applied after the end of
World War || and stereophotogrammetry - since 1954
(Katzarsky, 1988; Katzarsky and Kolewa, 1996).
6.2. Current Practice
The aerial photogrammetry for civil production purposes
in Bulgaria is concentrated in the following state
enterprises:
Geoplanproject Co., Sofía,
Geodesia Co., Plovdiv
National Centre of Cadastre Ltd., Sofia,
Research in Geodesy and Photogrammetry Ltd.,
Sofia,
Patproject Ltd., Sofia,
e Transproject Ltd., Sofia.
Geoplanproject and Geodesia implement analogue
stereoplotting of aerial photographs for compilation and
revision rural and urban topographic maps at scales of
1:10 000 up to 1:500. The National Centre of Cadastre
makes orthophotomaps at scales of 1:10 000 up to
1:2000. Research in Geodesy and Photogrammetry Ltd.
accomplishes mainly specific photogrammetric works.
Patproject and Transproject make maps at scales of
1:2000, 1:1000 and larger, as well as digital models for
the purposes of designing and reconstruction of
motorways, railways and structures, as well as for
inventory of the road and railway networks (Katzarsky
and Koleva, 1996).
6.3. The Photogrammetry in Compilation and
Revision of the Large-Scale Topographic Map
For compilation and revision of the topographic maps at
scales of 1:10 000, 1:5000 and 1:2000 aerial
photographs are taken mainly by wide angle metric aerial
photocameras (focal length 15 cm and picture size 23x23
cm) Zeiss - RMKA 15/23 and MRB 15/2323, as well as
Wild RC10 and RC 30 carried by the aeroplanes AN-30
(Russia) and L-410 (Czech). Depending on the map
scale and the physico-geographycal features of the
terrain, aerial photos are taken at scale of 1:20 000 up to
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
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