anbul 2004
EVALUATION OF THE POTENTIAL OF SPOT 5 HRG, HIGH RESOLUTION
SATELLITE IMAGERIES FOR 1:25000 SCALE MAPS REVISION
F. Sadeghi Naeeni Fard ^ *, A. Abootelebi “ , A. Eslami Rad ^
^^ Photogrammetry Dept. of National Cartographic Center of Iran, Meraj Ave., Azadi Sq., Tehran, lran.
(Sadeghi, Abootalebi, Eslami)@ncc.neda.net.ir
KEY WORDS: Updating, Remote Sensing, SPOT 5 HRG, Orthorectify, Feature Extraction, Information Content
ABSTRACT:
Nowadays, due to improvements in satellite technology, remote sensing data is used for mapping at different scales. In Iran, there is a
necessity to utilize satellite imagery as a complementary data source to aerial photographs. One of the main reasons for this, aside
from the usual advantages of this technology, is the ability to map and revise border areas having aerial access limitations due to
security reasons. This is especially true for Iran's 1:25000 scale base maps. In this paper the revision process of 1:25000 scale
topographic maps will be discussed and explained.
Generally, the satellite images can be applied either in the change detection phase or in applying the changes to the maps. In this
research, SPOT 5 HRG images have been used for revision of 1:25000 scale base maps. Successful exploitation of the accuracy
potential of SPOT 5 HRG depends on well defined and distributed GCPs and using of precise orthorectification process. Therefore
Toutin's spot model has been used to orthorectify SPOT 5 HRG image. Based on obtained results, SPOT 5 HRG images, while
having required planimetric accuracy at scale of 1:25000 (about 7.5m), provides the required information contents for such maps.
1. INTRODUCTION
Conventional mapping techniques in lran are still pegged on the use
of black and white aerial photographs and extensive fieldwork
exercises. This method is slow and cumbersome and is also very
costly to the extent that continuous national mapping remains far
beyond the realms of affordability for the countries. No wonder, most
national maps in Iran are very old and out dated and thus unsuitable
for planning and navigation purposes. Therefore there is an urgent
need to produce new maps or update existing ones.
At National Cartographic Center of Iran (NCC), production of
1:25000 scale topographic maps have been started since 1991 and
each map has 7.5'x 7.5' dimensions. Each block contains 96 sheets
and dimension of each block is 1.5° in longitude and 1° in latitude
(figure 1).
As mentioned, these maps are produced by photogrammetric method
using aerial photographs taken at 1:40000 scale.
One of the big problems that NCC is now facing is the changes on the
features during these years. As a result nearly all these maps have to
be revised and up dated as soon as possible.
Figure 1. Index of 1:25000 topographic maps of Iran.
In general, main source of changes that make map revision and
topographic databases updating a necessity consist of:
* Changes in data characteristics: when standard of data
characteristics is changed, every production must be
revised;
= Topographic changes: every change in topography must be
considered in databases;
« Changes in description and structural information of
features: such as changes in name, type and structures e.g.
features merging or feature dividing;
= Errors and mistakes during map production or revision
stage.
Because of the above mentioned factors, maps and topographic
databases must be updated when at due time.
2. BACKGROUND
The theoretical aspects of map revision include: planning for revision
(when), places to be revised (where) and method of revision (how).
There are three main alternative ways for planning revision or epoch
of revision. These are:
=" Cyclic revision, which would aim at the revision of the
whole series over a fixed period of years;
= Selective revision, which would try to achieve revision of
individual sheets by an order of priority that is governed by
rate of changes or urgency of demand and not by fixed
periods.
= Continuous revision, which relies on a continuous inflow of
information, field survey and etc to maintain sheets in an
up-to-date condition.
Continuous revision is ideal planning revision to achieve accurate and
precise information. Cadastral maps and large scale ones are
universally continuous revised. In this case, constant and certain
resources such as municipalities are used to collect information. This
is time consuming and costly method. Generally, for updating small
and medium scale coverage maps, cyclic revision is used.
