religious landmarks, to name just a few. These were
collected over the years, starting in the late 1930s. Thus, the
position and validity of many of these features are
questionable.
These features are then digitized off existing maps to enable
the production of the new map-series. Yet, one should not
“contaminate” the digital data base with features of non-
homogeneous origin. Such problems were foreseen and taken
care of when developing the remapping protocols and the
GIS data base model. Each of the features in the GIS
library also carries a SOURCE-CODE. This SOURCE-
CODE is a special pointer to the SOURCE-CODE look-up
table. This table contains the characteristics of the mapping,
including: method, date, planimetric and altimetric accuracy,
the mapping company code, etc. Thus, all the features that
were mapped off on 1:40,000-scale photographs taken at the
same date by the same photogrammetric company, will have
the same SOURCE-CODE. In the same manner, all features
that were digitized off an old existing topographic map, are
given the same source-code. This enables fast production of
new maps, and also the launching of a revision process of
validating the existence of these features by field surveyors.
Field Completion
As mentioned previously, field crews are sent to the newly
remapped areas in order to validate the existence of the
features that cannot be detected on the air photographs. This
aims also to resurvey those objects that are found, in order to
map them within the planimetric accuracy restriction of the
new National GIS Data Base.
During 1994, and most of 1995, some experiments were
performed over several areas of 400 sq.km. each. This is the
area covered by the traditional 1:50,000-scale map-series
quads. At first, field crews would set out, using new work
maps that were generated directly from the GIS Data Base,
using an inkjet or electrostatic plotters. The surveyors used
traditional methods of surveying, and were limited to
terrestrial transportation. Due to the restricted manpower
and other resources of the Survey, it took between 2-3 months
to cover an area of one quad. It was obvious that this was not
a solution for the field-completion surveying. At the end of
1995, the Survey launched an experiment using mobile GPS
surveying, complemented by transporting the field crews by
helicopter. This experiment showed a saving of 90% in
terms of time, and between 65-7596 in terms of cost. Not
only was it possible to remap, accurately, existing objects that
were “neglected” over the years, but it was also possible to
validate their existence. Thus, many of the features depicted
in old topographic maps were omitted as it was found they no
longer existed. In addition, many new objects were found
and added to the National GIS Data Base. This was made
possible by flying the surveyors and scouts over the area, thus
giving a better view, and enabling them to detect new objects.
Using a helicopter added to their mobility, and thus reduced
the time needed to move from one object to another.
Non-Spatial Data Completion
Non-spatial information becomes more and more in demand
as users begin to regard the spatial data as a base layer for
georeferencing the more “important” thematic (non-spatial)
646
data. This is a new domain for a mapping agency that is in
charge of acquiring, updating and distribution of spatial
information. Gathering non-spatial information focuses
mainly on urban areas. In such areas, the municipalities are
regarded as the best information source, and also as a
potential client for revised and updated town plans and maps.
Thus, the consumer has the motivation also to provide the
information, as by producing such non-spatial knowledge, he
is reimbursed by georeferencing these data.
Georeferencing is carried out by an interactive process. All
public and other activities are given a special code. This is
defined as a Secondary-code. There is no limitation on the
types and variety of these codes, and each of the features in
the Data Base may carry several Secondary-codes. Also, the
digital transfer standard, IEF'91 [Peled et al, 1991] is
open, and enables to attach as many as desired of these
Secondary-codes to the main Type-code (feature). A user-
friendly module was devised for this georefering. The
Secondary-codes are organized in logical groups, and are easy
to access, so the operator need not memorize them. This
“logic” was tested, and as some of the activities were defined
by several people in different groups, they appear in those
groups, e.g., the Muslim courts appear in the "judicial,"
“religious,” and “government” groups. By this concept, the
“logical-connectivity” of the operator will enable him to
access the same Secondary-code, no matter what initial
logical-group was chosen. Once a new activity is introduced,
it is processed by the GIS-Completion manager, given a
Secondary-code, added to a logical-group, and added to the
menu and the distribution standard.
This concept also enables the Survey to distribute information
acquired and coded by other authorities. These codes are
either given a prefix digit to identify the coding authority, or
are recoded by a pre-defined Transformation Look-up Table.
Such is the case with the forestry authority. All the flora
codes given by this authority are kept, intact as secondary-
codes. The Survey itself has Type-codes only for trees,
bushes, forests, etc. The actual type of the trees are coded
according to the Secondary-codes given by the forestry
authority.
MAP REVISION
Map revision is envisaged as a by-product of the data base
revision and updating. Here again, there is utilization of the
SOURCE-CODE. All data extracted from the GIS data base
are kept in a special library which is referred to as the
“Cartographic GIS.” These files are the exact copy of the
original data base, and should not be confused with the
“cartographic” copy (backup) of the final digital file used to
generate the map. These files are the result of tedious work
of cartographic treatment, hierarchy manipulation, and other
procedures aiming for a better quality visual product, namely
the map, that depict, but not necessarily copy, the spatial and
non-spatial data stored in the National GIS data base.
The simple solution is to revise the map by running the map
production process from starting point, using the updated
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
