sence of 
terrain 
1 points, 
contour 
trend of 
aking of 
1s later 
nd the 
yrdinates 
n values 
'ocedure 
e object 
points is 
que was 
id-white 
dericton 
taken at 
e angle 
spreads 
River, is 
ea level. 
' incline 
the city 
canning 
 ScanJet 
'ast and 
er were 
lize the 
images. 
vailable 
tion was 
) or 118 
] size of 
ground. 
| to 256 
exterior 
rom l:1 
al is 1.0 
vation is 
lifferent 
Photo 1. 
] streets, 
a sports 
ich were 
then computed using the correlation and the 
space intersection software, and compared 
with the coordinates measured on the 1:1 200 
scale maps [Chen, 1993]. 
3.2 Test Results and Discussion 
The results of the test are summarized in 
Table 1. 
The RMSEs are the root mean square errors 
of the planimetric coordinates obtained by 
the pseudo-stereo mapping technique with 
respect to those measured in the 1:1200 scale 
maps. The notation "26 « 1.5 m", etc. means 
the percentage of the check points with 
differences. smaller than:.1.5. m, etc... The 
photographs for this test were taken from a 
block flown for 1:10 000 scale mapping. 
Therefore the assessment of the results are 
based on the degree of compliance with the 
map accuracy standards applicable at that 
scale. 
The accuracy specification for the "Urban 
and Resource Digital Map Base" in the "Land 
and Water Information Standards Manual" 
states [NBGIC, 1991]: 
Ninety percent (90%) of all “well defined 
features” must fall within the positional 
accuracy ...[2.5m]. Well-defined features are 
those whose positional accuracy is not 
adversely affected by vegetative cover. 
Accuracy of the digital data (point, line, 
area) can be defined as the difference 
between the position of the associated data in 
the digital file and the real position of the 
represented features on the earth. 
Although this requirement is rather strict, 
87% of the well defined feature points 
satisfied it. This is only 3% below the 90% 
tolerance. For graphical map production, the 
generally accepted tolerance in North 
America is 0.5 mm at publication scale, at the 
9096 confidence level. This corresponds to 
5.0 m for the 1:10 000 scale. All points were 
Within this tolerance. 
The following points should be considered to 
put the results in proper perspective: 
l. The pixel size of the digitization was 3.0 
m on the ground, which is larger than the 
2.5m tolerance set by the map accuracy 
standards. 
2. The stage plate of the scanner used was 
8.5 x 14 inches, which is narrower than 
141 
the size of the photographs. Thus, two of 
the primary corner fiducial marks and one 
of the secondary marks along the edges of 
the photographs were missed. This 
introduced an uncertainty in the interior 
orientation. 
3. The particular scanner employed is only 
suitable for digitizing opaque 
photographic prints. The poor 
dimensional stability of paper is of course 
a source of significant distortion. 
4. Because of storage limitations in the 
computer, only the overlapping areas of 
the photographs were kept on the files 
and used for selecting GCPs. Therefore, 
the geometry of the bundle of rays in the 
space resection were not the most 
favorable. 
5: The'6l:15:200 scale maps: used for 
comparison was accepted as error free. 
Under the above circumstances the test 
results can be considered satisfactory and 
accepted as a proof of the feasibility of the 
pseudo-stereo mapping technique developed. 
Further tests are of course needed to fully 
validate and improve this technique. 
4. CONCLUSIONS 
The pseudo-stereo mapping technique is 
applicable when no orthoimages or DEMs 
are available, or when the DEM is out of date 
and the relief displacement is too significant 
to be ignored. This technique has been 
successfully implemented in a GIS as proven 
by the outcome of an experiment. The ability 
to perform soft copy mapping in a GIS has 
the advantage that both the image and the 
map reside and are manipulated in the same 
workstation. 
It is true that the results of the test do not 
entirely satisfy the map accuracy standards 
set for the digital base map production. 
Firstly, the experiment was conducted under 
less than ideal conditions for precision 
mapping, as explained earlier. Secondly, the 
objective of this development was to provide 
tools for thematic mapping, performed by 
non-photogrammetrists, when accuracy 
requirements are not as stringent as in basic 
mapping. Thirdly, simplicity and low-cost 
were also objectives. This explains the