Geography Reference
In-Depth Information
conventional methodologies. In such case the topographic features can be obtained for the
most extensive areas of our country, meeting a demand of great part of the studies and
activities related to topographic representation.
The interest in investigation on altimetry spawned by orbital products arises from the fact
that planimetry has already been studied, both in meeting thematic and reference
cartography. Besides the need of studies related to altimetry, this category has been raising
growing uses and interest. For some examples of the use of altimetry in studies related to
thematic cartography, see [3-7]. To exemplify applications related to reference cartography,
see [8-12].
In the case of Brazil, cartography still presents serious problems related to the updating of
the existent bases and availability of appropriate scales for the most different studies in [13],
especially in scales with greater detail of systematic mapping, as for instance, 1:100,000 and
1:50,000 which are very useful in environmental and urban studies.
3. Accuracy of the planimetric and altimetric representations:
Case studies
A proposal to minimize the problems presented - rejection of indiscriminate utilization - is the
creation of a culture for assessment of the quality and validation of the generated products.
This way, maybe, we come closer to know what is real. There is a norm called Cartographic
Accuracy Standard (PEC, in Portuguese - [14]) to classify cartographic products. However its
application has always been limited. PEC was created in the 1980's, when cartography was still
in the analog phase. With the change to digital cartography, new approaches are required
regarding assessment of planimetric, and especially altimetric accuracy. In [15] it is possible to
see a discussion on the use of PEC in present days, calling attention for the need of changes
and inclusion of statistical tests, not foreseen in the present norm.
PEC makes reference to the assessment of final products through the use of control points
for checking how much the points located on a map deviate from their homologous located
on the ground. For each quality class - which can also be understood as accuracy - a
standard value is specified to be reached by at least 90% of the points, as well as a limit
value for the Mean Square Error - understood as synonymous of standard deviation. Said
simply, this norm applies both for planimetric as altimetric assessments.
Notwithstanding all our concerns regarding the quantity and quality of information that can
be extracted from remote sensing products, the volume of products originated from new
sensors grows every day and the demand for investigation regarding accuracy of its
geometry, considering what is established in the PEC, is still very large. As suggested above,
probably this is explained by some factors such as insufficient knowledge of such need or
the lack of norms or standards for other types of assessments that may be used as reference.
ESPAÇO Remote Sensing and Environmental Studies Laboratory of the Department of
Geography of the Federal University of Rio de Janeiro (UFRJ) has a research line aimed at
assessment regarding the geometry of several products originated from remote sensing since
