triangulation results due to more homogeneous disposition of 
control points, etc. Further on, a regular quality control of CAS 
photos, aerial triangulation and digital orthophoto maps started 
in 1999/2000. 
A database of basic photogrammetric products has been 
established as well, on the basis of the conceptual model 
proposed in the revised CAS project. Orientation parameters of 
photos computed in aerial triangulation are entered in the 
database, together with some other data (references to aerial 
survey project). Images (scanned photos) are stored separately 
asa file-database. 
5.2 Quality evaluation of scanned photos 
The increasing use of digital photogrammetry leads to a 
constantly growing demand for scanned aerial photos. Whereas, 
until recently, digitised aerial photos were primarily used for 
orthophoto production, the field of digital applications is now 
rapidly and continuously expanding. In addition to digital 
stereoplotting, the emphasis is placed today on digital 
aerotriangulation and matching techniques for DEM generation, 
to mention only two examples. These latter applications in 
particular, make extremely critical demands on the quality of 
the digital source material, which can only be guaranteed by a 
high-precision photogrammetric scanner. These scanners are 
specially designed to meet the requirements of precision 
photogrammetry, where in particular the geometric 
requirements are very high. Other scanners could be used under 
special conditions (e.g. proper calibration method), but this 
should be only in case that no precise photogrammetric scanner 
is available. 
Two precise photogrammetric scanners are available in 
Slovenia for scanning photos from aerial survey. 
Photogrammetric scanners enables the scanning of original 
photos without any need to cut the film and without any 
intermediate photographic processes for the generation of 
original digital images, fully automatic digitization of the 
images and a high geometric and radiometric accuracy. 
It is very important that a scanner is maintained in accordance 
with manufacturer instruction. Geometric accuracy is assured 
with calibration procedure, which is usually automated. A glass 
calibration plate with engraved crosses is used, and a report is 
produced at the end of the procedure. The residuals after 
adjustment ranges about few microns. 
Control of aerial photos of Slovenian cyclic aerial survey 
consists of two steps: 
e visual control of all photographic material (negative 
originals on film rolls), 
e test scanning on a sample. 
The original negative films must be handled very carefully. The 
visual control must is done under laboratory conditions (clean 
room, using gloves, normal temperatures and humidity of the 
air, etc.). The complete film is checked for eventual physical 
damages of the film (scratches). The densitometric values are 
measured as well. 
140 
     
REPORT ON CONTROL. OF SCANNED PHOTO | 034-01 | 664 | 4524 
Project: ^ tirska Bistrica 
Photo scale: 1.17 500 
Photogrammetric block: — 57 
FILM: 
Nu: 034-01. Manufacturer: AGFA Type! AVIPHOT = DIN/ASA: PAN 80 POS... COLOR / 
CAMERA LENS FLIGHT. 
Type: RC-30 Type: 15/4 UAG-S CAS 01 22.07.2001 08:46:59 
Ser. No. No data Ser. No: 13351 sup — 864 phnin: 4524 
Focus 153,593 mm 
IMAGE QUALITY u SCANNING 
se meddle Cup Scanner ZEISS - SCAl 
Scralch A Ser No. 148544 
Hol spot: * m File 4524 . PYR 
Clouds v Resolution 14 gm 1814 dai 
Unsharge: Y c 
Producer Gl 
Operater 
  
  
  
  
  
  
  
  
  
Figure 2. Example of a report on control of scanned photos 
Scanning is done only on sample photos (every 30" photo, 
including the first and the last photo in the roll). A report on 
quality control is produced. A certificate is given in the report, 
with the main data and final evaluation results. Detailed report 
on geometric, radiometric and visual control is given as well. 
As an example, an extraction of a report of test scanning is 
presented in the Figure 2. 
5.3 Quality evaluation of orthophoto map 
Digital orthophoto map (DOP5) in scale 1 : 5000 is nowadays a 
standard product of geodetic service. At the end of 2002, the 
entire territory of Slovenia was covered with this map, with the 
oldest orthophoto map sheets dating from 1997. It is produced 
from aerial photos of Cyclic Aerial Survey. For the purpose of 
production of DOPS, photos are scanned with photogrammetric 
scanners with the resolution 14 um or 15 um (depends on the 
type of scanner) and the final resolution of the map is 0.5 m on 
the terrain. It is available in TIF files and also hardcopies are 
produced on a film. In addition to resampled image, the 
geographical names from the Register of Geographical Names 
are positioned in the map. In the last three years, the produced 
digital orthophoto map sheets have been controlled with full 
inspection (i.e. every map sheet) with visual inspection and 
formal control procedures. 
5.4 Quality control of digital elevation model 
In Slovenia, digital elevation model with a grid cell of 25 m 
(shortly DEM 25) is produced with matching methods as a by- 
  
  
  
  
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