Or
he
st
ne
or
ed
EFFECTIVE WAYS TO REVISE DIGITAL MAPS AND GIS DATABASES IN URBAN AREAS
Gerhard Sehnalek
Sr. Project Manager
Analytical Surveys, Inc., Colorado Springs, USA
Commission IV, Working Group 4
KEY WORDS: Revision, Urban, DEM/DTM, GIS, Method
ABSTRACT
The objective of this paper is to provide a methodology developed by Analytical Surveys, Inc. (ASI) for revisions of large-
scale maps in urban areas. While the GIS sector is booming the demand for map data upgrading and map revision
increases. There is a huge demand for better and more actual map information. Standard map revision techniques are not
able to fulfill these demands because of the conditions of the existing (old) digital map data. A brief description of problems
encountered with existing (old) digital map data that may have been translated from the original compilation files to a
particular Computer Aided Design (CAD) or Geographic Information System (GIS) environment. During this process data
may have been lost, distorted or wrong classified. Prior to the actual revision process the user's files are translated back to
photogrammetric files and enhanced to allow to view the old map superimposed upon the new photography with a minimal
displacement. In order to comply with the requirements to view the data within a stereoscopic or photogrammetric model it
is necessary to add elevation values to the old 2-D maps. The development of digital elevation models (DEM) from existing
data is reviewed.
1 Introduction
For the past 15 years municipalities and local
government agencies all over the world contracted digital
mapping services to produce large-scale maps. In the
past five years the increasing demand for reliable and
comprehensive digital data for various purposes
governed the need for the integration of diverse
geographic information, managed by a Geographic
Information System (GIS). The objective of this paper is
to provide a methodology for revision of large-scale
maps in urban areas and especially addresses the
problems encountered with existing (old) digital map data
which may have been already translated from the original
photogrammetric files to a particular Computer Aided
Design (CAD) or GIS software environment.
Analytical Surveys, Inc., (ASI) has developed a method
in which prior to the actual revision process, the user's
files are translated back to the photogrammetric files and
enhanced to allow to view the old map superimposed
upon the new photography with minimal displacement.
Because of the requirement to be able to view the data in
an analytical stereoplotter it is necessary to add elevation
values to the old 2-D data. The discussed approach and
the associated updating procedures are based on
several projects successfully completed by Analytical
Surveys, Inc.
759
2 Background
Within the last five years several cities and counties
throughout the United States have contracted Analytical
Surveys, Inc. (ASI), a digital mapping company located in
Colorado Springs, CO, to undertake multiple tasks
projects: revision of the digital source data, translation
into the format of the new target system and
development of a GIS database from these new
structured digital files.
With the shift from the analogue to the “digital Era” in the
last two decades users and providers of digital maps
data have successfully used the tremendous
enhancements of computers and software. Analysis of
digital maps produced in the 1980’s showed that data
collection was limited to the basic functions of CAD
systems. The large-scale maps generated over urban
areas at scales of 1:1,200 and 1:2,400 (1”=100’ and
12200) were typically referred as “CAD maps” and had
been used primarily for plotting, planning and other basic
engineering tasks. In the last five years this was
complemented with the introduction of advanced CAD
software and even more sophisticated Geographic
Information Systems (GIS). Even so users have become
more knowledgeable in the use of new software and
hardware the content and the quality of the existing
digital maps has not improved in the same pace.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
