The following projects have been published since then.
This sub-web contains Mahes Visvalingam's contributions to the work of the
British Cartographic Society and the International Cartographic
Associations' Commission on Theoretical Cartography. The papers
are philosophical and deal with definitions, map-induced semiosis,
cartosemiotics, etc. The pages contain links to other sites.
- Contents Page (Last revised Mar 2003)
(Last revised Jan 2003)
- Scope of Digital Cartography
(Uploaded June 2003)
- Cartosemiotics (Last revised April
- Visualisation, ViSC and Scientific Insight
(Uploaded June 2003)
Census Analysis and the Role of Maps in Social
- Data Rich - Information Poor
Lecture by Mahes Visvalingam on Friday
October 20, 2000 at IAP2K,
the annual symposium of the UK Institution of Analysts & Programmers, which was
held in association with the British Computer Society at Trinity House, London. The talk focused on the problems involved in defining
statistical indicators of local conditions.
- Phil Wade's Fortran code for The Douglas-Peucker Algorithm in
CISRG DP 4.
- Evaluation of the Douglas-Peucker Algorithm by Visvalingam and Whyatt
(1990) CISRG DP 6.
- Cartographic Algorithms: problems of
implementation and evaluation and the impact of digitising errors in
CISRG DP 8
- Visvalingam's algorithm for line generalisation
CISRG DP 10
- Other Comparisons of Visvalingam's
algorithm with Douglas-Peucker and Bendsimplify algorithms
- Visvalingam and Williamson (1995) in Cartography and GIS -
- Visvalingam and Herbert (1999) in Cartography and GIS - original
pre-published CISRG DP 16 being scanned.
- Line Generalisation Algorithms and
- Deconstructing Fractals
- Exercises undertaken by members of the Design Group of the British
Visvalingam (1999) in Cartographic J
- also paper by Visvalingam and Brown (1999)
- implications for cartographic education in
CISRG DP 17
- The need to segment line features into semantic areal entities for map
generalisation - presented by Visvalingam at ICA 1999;
page includes links to:
- a rather rambling draft paper seeking to explain my position and approach
- powerpoint slides used at ICA
- illustrations were based on Herbert's MSc project on line segmentation.
This paper linked my interests in generalisation with our research in spatial
Spatial Data Modelling
(Under construction - last revised September 2005)
This sub-web was created in response to
a number of recent email enquiries on CISRG research, dating from 1985 to
1994, on spatial data models for GIS. We undertook a series of
investigations in collaboration with the Ordnance Survey into map data
models and algorithms for validating link-and-node structured vectors and for
automatic extraction of implied areal topographic objects. The recently
launched Ordnance Survey (OS) MasterMapTM uses unique Topographic Identifiers
(TOID) and National Grid references for management and cross-linking of
disparate geo-referenced databases based on primitive regions as suggested by the CISRG
in the mid 1980s.
Relevant CISRG references are:
Areal Units and the
Linking of Data : some conceptual issues
by Mahes Visvalingam, Chapter 2 in Worrall L
(ed) Spatial Analysis and Spatial Policy Using Geographic Information Systems
(Belhaven Press, London), 1991, 12 - 37. This chapter, posted here with
permission from the editor, is a review of the issues involved in the design
of basic spatial units (BSUs).
CISRG Discussion Paper 1
entitled From Line Geometry to Area
Topology provides a detailed account of our research on spatial
data modelling and algorithms for casting data. These results were
published in The Computer Journal. Readers may wish to note the critique
of our approach by Laurini and Thompson (1992).
CISRG Discussion Paper 11
entitled Area Topology for Road Extraction and Topographic Data Validation
demonstrates an application of the Spatial Data Model described in CISRG DP 1
for extracting and validating incompletely defined topographic
objects from link-and-node structured map data and thereby detecting
topological errors in the source data and deficiencies in the map model
CISRG Discussion Paper 12
entitled Global dimensions for
the recognition of prototypical urban roads in large scale vector
topographic maps noted that three global dimensions, including two novel
ones proposed by the CISRG, are useful for recognising prototypical roads
from the geometric information alone in link-and-node structured map data.
Roads extracted through use of semantic codes (see CISRG DP11) can then be
checked against the results of recognition to provide yet another means for
validating topographic data.
Promotion of Independent Research
(last revised March 2003 )
The research undertaken by Mahes
Visvalingam has been independent and largely unfunded. As such, she is
keen to encourage the efforts of other independent researchers
through this sub-web (last updated on
Page maintained by: Mahes Visvalingam
Last updated on April 2006
Cartographic Information Systems Research Group, University of