Geography Reference
In-Depth Information
7. Issues (still) remaining: Some limitations persisting and potentialities
observed
Besides being somewhat limited, the evaluations using PEC made sense for analog
mapping, whose construction processes were more vulnerable to graphic issues, such as the
tracing of the elements properly. Considering altimetry, it becomes even less valid for the
digital data, because reference is made to the contour lines interval, without mentioning
specific scales. In several applications, nowadays, it is possible to have a DTM or DEM and,
based on them, automatically extract the contour lines, in case required. But what matters is
that the primary product tends to be the digital model and not the contour lines, which are
dispensable for most of the applications, except in the case when it is desired to print the
base with the altimetry represented in a way to allow quantitative estimates. According to
this reasoning, it is necessary to assess the accuracy of the DTM or DEM, because they
normally are inputs from derived products, although the official Brazilian norm does not
make any reference to this type of product. Obviously one should maintain the assessment
of the contour lines in the cases where they represent the altimetry.
Even considering the PEC as reference, it can only be applied for assessment of the
geometry of reference cartography products. There is no official norm for
assessment/evaluation of thematic cartography products in Brazil. Therefore, thematic
mappings present accuracies - both in terms of geometry as contents - which are either not
assessed or which remain to be decided by the specifications of their producers. The
importance of the establishment of norms is emphasized once more, or, at least the
establishment of national standards that facilitate data interchange with levels of accuracy
that can be known and compared. Brazil is presently making an endeavor to divulge its
National Spatial Data Infrastructure (INDE), expanding the utilization of geospatial data in
an appropriate manner. Such an endeavor also focuses on the adoption and dissemination
for the use/generation of metadata. In this context, the knowledge of the accuracy of the
products, whether referential or thematic, is mandatory.
It is clear that both for the reference cartography as for the thematic cartography the
assessment should not be restricted to the accuracy of the geometry, but should consider
also the reliability of what is being represented - i.e., its actual contents. In this context,
some items to be considered are: what is represented, the amount of elements presented, the
taxonomic level reached, the level of detail, etc. Obviously, for reference cartography some
elements may have greater relevance while in the thematic cartography others may deserve
more attention. It is necessary to disseminate among the users and producers of
cartographic data the importance to know the quality, both of the geometry as the contents,
the detailing of the mapping, always assessed considering the scale adopted. Despite
seeming obvious, it is quite common to find the distribution of products presented as
compatible with a certain scale, but in the assessment made, one finds that the concern was
merely with the accuracy for geolocation, i.e., with the geometry. Among the non-specialist
users the problem is even greater, because they rely more easily on the information
provided and end up acquiring products which do not correspond to their needs and, when
