The digital orthophotos are used as a raster 
backdrop for the vector data to be updated. The 
updating of the database is performed by 
interactively extracting the new planimetric 
features from the image in a monoscopic mode 
using heads-up digitizing. The digitizing from the 
screen can be done on cheaper 
workstations in a distributed, 
process are illustrated in Figure 1. 
3. SYSTEM REQUIREMENTS 
To meet the production 
methodology for revising “old” 
systems used must offer 
diapositives of aerial photographs, production of 
digital orthophotos and mosaics from existing DEM 
Data input 
  
NTDB 
requirements of this 
vector data, the 
certain functionality, 
such as: generation of digital images by scanning 
non-stereo 
networked 
processing environment. The steps of the revision 
4. IMPLEMENTATION 
A pilot project was carried out in order to 
prototype the implementation of the proposed 
methodology «nd its integration with the available 
in-house systems. This project involved the 
production of mosaicked orthophotos covering the 
Jasper 1:50 000 NTS map. The area covered by 
the JASPER, Alberta/British Columbia map is 
32X26sq.km. 
4.1 Orthoimage generation 
The task of generating the digital 
orthophotomosaics involved the scanning of 25 
aerial photos flown at a scale of 1:60 000. The 
photographs were digitized at resolution of 
1000dpi (1.5m at ground) and quantized at 256 
gray levels (8-bit images) using the Helava/Leica 
Data revision process 
  
  
1:50000 data 
  
  
  
Generation of orthophotomosaics 
   
   
Loading of data 7 E 
  
  
  
ss 
  
  
  
  
Photography 
  
  
—J» Scanning of the photographs 
  
  
  
  
  
  
"^ | Determination of exterior 
Control points orientation elements (EOE) 
  
  
  
  
  
  
  
... | DEM (and contour lines) 
: generation 
  
  
Y 
  
     
| using the EOE, DEM and resampling | 
| Digital orthophoto generation | 
= | | | - collection of revised data aided by field 
  
Georeferencing of v Qu. 
===] orthophotomosaic quads | 
Revision of "old" vector data . 
| - integration of raster and vector data 
| - time-stamping of "new" data 
| | - image enhancement and interpretation 
| | - change detection 
  
verification 
————Ó 
  
Editing of contour lines 
  
  
  
  
Generation of the orthophotomosaic - 
  
  
  
  
  
  
  
  
  
a : Quality control 
  
  
  
  
  
  
Updating of NTDB, cartographic 
representation and NTS map production 
Figure 1: Database and map revision process 
or by generating the DEM from the newly digitized 
photographs using stereo-image matching 
techniques, image processing functions, 
integration of vector and raster data capabilities, 
digital mapping functions, topology creation and 
cartographic editing. These capabilities are found 
in the  softcopy (digital) photogrammetric 
workstations and in vector-raster GIS systems. 
96 
DSW100 scanning workstation. 
The Helava/Leica DPW770 digital photogrammetric 
workstation was used for the DEM and orthoimage 
generation. The exterior orientation parameters 
were determined using the available control points 
from the Aerial Survey Database (ASDB). The 
control points were transferred and cross pugged 
to current photography from previous 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996 
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