International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B6. Istanbul 2004
measurement of ground control points (GCPs), and processing
softwares will follow accordingly.
Before decribing some practical production of a such kind of
maps (from par. 3 on), basic guidelines are shown, collecting
them in 5 main aspects.
2.1
P
Sustainable cost
It would seem an evidence that, speaking about of a
cartography for the developing countries, the economic problem
may represents a real bottle-neck. Results of a research project
leaded by EuroSDR (Holland er al, 2002) have shown a
comparison between costs of upgrading topographic maps at
1:10,000 scale by means of three different data sources (we
limit our interest only to products among those analysed, being
the others of scarce interest for practical use):
aerial photos;
IKONOS Geo Ortho-Kit;
IKONOS Carterra Geo-Product ortho-rectified by PCI
software.
WwW 2 —
Considering all tasks needed to upgrade maps, such as flight
planning, imagery, aerial triangulation, GCP measurement,
DEM, ortho-rectification and data capture/feature extraction,
the process based on airborne data is the cheapest. The methods
based on IKONOS data (panchromatic images at 1 m ground
resolution are assumed) have results in a 56% of larger costs by
using data-set (2), and only 6% larger in case (3). Authors
noticed that costs of case (1) derived from a particularly
favourable condition, because refers to an important mapping
agency were aerial photography, GCPs, DEM and digital
photogrammetric workstations are already available. The use of
HRSI would be even more actractive in developing countries,
where these resources are not so plentiful, resulting in the only
sustainable approach to provide mapping.
2.2 Fast production process
As stated in its definition, one of the fundamental peculiarity of
FMAPP is the fast acquisition process, due to the need to
provide maps for large regions as well. In order to do this, the
production workflow is the following:
1. satellite data acquisition (recovering of archives data or
commission of a new capture);
GCPs measurement;
orientation and orthorectification (possibly the DEM
generation, if not already provided);
4. data capture and feature extraction.
Uu N
Concerning timely of this process, the critical stage is the data
acquisition. Archives collecting already available images are
directly accessible on-line via WEB by:
=» Space Imaging (www.spaceimaging.com), which delivers
IKONOS data;
=» DigitalGlobe
QuickBird data
= Spotlmage (www.sirius.spotimage.com), which delivers
SPOT-5 data.
(www.digitalglobe.com), which delivers
Currently, no archive is available for Eros-Al data, being
necessary to ask vendors (www.imagesatintl.com) about which
images have been already collected over the interested area.
However, in case images covering large areas are needed as in
case of regional mapping projects, recent archives data will be
very difficult to be found, and images must be ordered. The
time nedeed to schedule the data capture over the required area
may be even of a few months, and images with a too wide cloud
coverage may easily happen. Nevertheless, the problem of
waiting for the data acquisition exist also in case of using aerial
photos.
All the other tasks need a smaller time to be completed,
depending on the mapping organization and not merely on the
image vendor. Furthermore, barring GCP measurement, other
stages are only data processing operations, involving no
logisthic and organizing problems.
2.3 Reduce need of infrastructures
The principal idea of FMAPP is the use on HRSI, avoiding the
need of aerial photography and of all infrastructures connetted
to this. The only HW and SW requirements are listed in the
following:
e workstation for different stages of data processing;
oe GPS receivers for GCP measurement (either one
master and more rover stations);
e GPS data processing SW;
e. SW for image registration/orthorectification;
e mapping SW for data capturecapture/feature
extraction;
e GIS SW for management of the resulting spatial
database and for the generation of digital and
hardcopy maps.
2.4 Map contents
The basic geometric map data of FMAPP are digital
orthophotos at mid-scale. It seems that for a not yet mapped
region, a coverage of orthophotos at 1:10,000 scale may be a
very important results for land planning and management. The
availability of ortho-rectified data would allow to reduce the
number of vector information to capture, with the obvious
decrease of time and costs. We retain that, however, some
vector layers should be derived, according to the particular
needs of the country developing the mapping project.
Moreover, information about geographic names should be
externally provided. Modern GPS technology have provided the
users with a large variety of GIS datalogger palm receiver,
which are able to acquire geocoded information directly on the
field, by filling in a pre-defined DB. GPS signal recorded by
these receivers may be processed in a differential mode,
resulting in even sub-meters accuracies (depending on the
distance from the master station). Thanks to a GPS receiver of
such a kind, information that cannot be colletted from the
imagery can be supplied and integrated in the spatial DB.
Collected vector layers and ortho-images have been thought as
the initial data constituting a spatial DB, which will be then
integrated by adding up further information. Each object in the
database is linked to an attribute table, specifying some
important characteristics of it. The attribute table is made up by
a set of attributes which are common to all possible features.
Then specialized attributes are introduced for particular kinds of
features; e.g., in case of roads, attributes describing the class of
the road, which kinds of vehicle can run on it and the like
should be introduced.
