t, à 
iven 
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WS. 
ed a 
for 
ving 
dan 
Dn of 
cale 
518 
ing, 
the 
rvey 
here 
nous 
have 
d to 
date 
the 
to 
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the 
of 
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ates 
n'as 
e is 
ting 
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onal 
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duce 
Cost 
ting 
soin 
'elop 
face 
The 
lenus 
ate 
operator interaction during the 
updating process, and the revised 
updating methodology simplifies the 
paperwork and file handling routines 
associated with recording the change 
information. These changes have 
resulted in a saving of 50% in 
operator time enabling faster 
throughput of updated information and 
increased cost effectiveness. 
Production of Software which can not 
only produce, but also accept, change 
only data 
OSNI is now in a position to supply 
change only information from the 
large scale database to NIGIS 
partners and it is recognised that 
this: willc-provide: à’ more::-cost 
effective method for updating 
customer databases rather than 
resupplying complete tiles. While 
none of the NIGIS partners has to 
date indicated that they are in a 
position to handle change only 
information, it is believed that now 
that change only data is available 
from OSNI, GIS vendors supporting 
such clients within Northern Ireland 
will be required to consider 
developing procedures to utilise that 
data. 
Data Compatibility 
Data compatibility is fundamental to 
successful GIS implementation and 
user acceptance of such systems. OSNI 
1s acutely aware of this as NIGIS 
continues to develop and to further 
progress the issue a special NIGIS 
Standards Sub-committee was created 
to make recommendations. Issues 
examined were the adoption of 
appropriate data transfer standards 
for map based information, Street 
Gazetteer, Land/Property Gazetteer 
and address based data. 
This sub-committee has since 
published its findings and 
recommended that National Transfer 
Format (NTF) Version 2.0, Level 3 as 
defined in British Standard BS7567, 
should be the NIGIS interchange 
format. Adoption of BS7567 by all 
35 
NIGIS partner organisations will 
greatly facilitate data exchange 
between them and assuming this 
standard is further accepted by the 
Northern Ireland GIS community 
generally, will aid software vendors 
in the development of systems to 
handle both new and updated digital 
topographic data. 
PROGRESS SUMMARY 
Ins: the co main this D progress” “has 
resulted from in-house development 
based on existing software and 
refinements to existing flowlines. 
Ibo/rhas ->not7 ‘addressed to any 
significant extent improving the 
data collection part of the updating 
operation. While many advances have 
been made in respect of ground 
collection of revisions by pen 
computers, as far as user friendly, 
cost-effective large scales updating 
procedures are concerned it is felt 
that the future must still rely 
heavily on aerial photography. 
THE IMPORTANCE OF PHOTOGRAMMETRY TO 
COST EFFECTIVE UPDATING 
Traditionally large-scale 
topo-graphic data has tended to be 
revised using a mix of 
photo-grammetric and ground survey 
methods. The latter is inherently 
expensive irrespective of whether 
revisions are captured digitally, or 
manually with subsequent digitising. 
Aerial photography offers much 
greater potential and used within 
digital photogrammetric systems 
provides an increasingly effective 
means of carrying out the revision 
process using the principle of 
superimposition. The benefits of 
superimposition where the existing 
database is overlaid on the 
photographic image are considerable 
and particularly relevant to 
efficient database revision. 
Superimposition is also possible 
through enhanced analytical systems 
but it is a costly upgrade, and 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996