present time CCM is in a transition period from 
combined analogue and digital production 
scenarios for the production and maintenance of 
the NTS maps to a fully digital solution. With 
the increase in the supply of new digital data 
and the growing client demand for digital 
products, the implementation of digital map 
revision technology has been accelerated. This 
paper describes the pilot project that was carried 
out to investigated the potential of using 
1:50 000 digital data and LANDSAT TM 
imagery, and digitized aerial photography to 
derive/revise the data required to produce the 
1:250 000 and 1:50 000 NTS maps, 
respectively. 
2.0 SYSTEM REQUIREMENTS AND 
SELECTION 
Map revision operations from aerial 
photographs and satellite images require several 
steps: interpretation, change detection, 
collection of new data, and integration of old 
and new data in the database. One of the 
effective methods for extraction of new data is 
by the superimposition of the existing digital 
map data over recent aerial photographs/satellite 
images and update the database by collecting the 
new information. The superimposition and the 
data collection can be performed in several ways 
(e.g., Welch, 1989; Derenyi and Shih, 1991; 
Bouloukos et al. 1992). Image processing 
functions are also required for the enhancement 
of the raster images to facilitate the interpretation 
and change detection. The revision of the 
1:250 000 maps was based on a twofolded 
approach. First, recent larger scale maps such 
asthe 1:50 000 digital maps are generalized to 
derive the smaller scale maps. Second, satellite 
imagery such as the Landsat TM is used as 
backdrop to the 1:250 000 digital data and the 
detected changes are screen-digitized thus 
updating directly the data set. The approach 
tested for updating the 1:50 000 maps is digital 
mono-orthocompilation, that is the on-screen 
digitization of planimetric details from 
registered digital orthophotographs /mosaics. 
The digital orthophotographs are displayed as 
backdrop to the 1:50 000 digital data and the 
newly digitized data updates the vector data set. 
These requirements are met by having a vector- 
based topographic mapping and GIS system 
integrated with raster data handling capability. 
The integration should extend to the operational 
and functional levels. The system used is 
CARIS (Computer Aided Resource Information 
System), a comprehensive GIS system 
produced by Universal Systems Ltd. of 
Fredericton, New Brunswick, Canada. CARIS 
was originally a vector-based GIS system, 
which has recently extended its capabilities to 
fully integrate raster type data (Derenyi, 1991; 
Halim et al., 1992). For topographic digital 
mapping and GIS applications CARIS software 
functionality includes: 2 and 3-D data capture, 
interactive editing, generalization and 
cartographic editing, topological creation, 
interactive data analysis, off-line data analysis, 
digital terrain modeling, semi-automated map 
input and application support. 
The raster image requirements are addressed in 
the areas of image display and image analysis. 
To display an image the following commands 
are available (USL, 1992): set up the colour 
map, enable the drawing of raster image, select 
the layers to be display, draw the selected 
layers, disable drawing of raster images and 
display pixel value. Image interpretation is 
supported interactively by contrast enhancement 
using either histogram equalization or user 
specified histogram, piecewise linear stretch, 
neighbourhood averaging, and bi-directional 
gradient. Also, available are: image registration 
and rectification including resampling, ortho- 
image generation and image classification 
modules. 
The system configuration for the pilot project 
consists of CARIS UNIX version 4.2.4 
running on Sun SPARCstations 2 and 10. 
3.0 REVISION OF 1:250 000 NTS MAPS 
The objectives of this part of the project were to 
update an area of a 1:250 000 digital data set, 
first by generalizing the 1:50 000 data set, and 
secondly by revising the data set using the 
Landsat TM image. The area of the 1:250 000 
sheet, 31I Trois-Riviéres, corresponding to the 
1:50 000 map 3113 of Sorel, was chosen as the 
pilot site for the investigation. This area also 
has 1:50 000 stereo compiled data coverage. 
Sheet 31I is currently being manually revised in 
the Map Revision Section using hard copy 
1:50 000 maps and Landsat TM imagery 
(Turner and Stafford, 1987). This sheet was 
chosen because of the availability of a current 
1:50 000 digital file and that the results of the 
pilot project could be compared with the 
manually revised product. The materials 
required for the pilot project revision were the 
1:250 000 digital file, 1:50 000 digital data, 
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