Geography Reference
In-Depth Information
trying to extract an amount of information proportional to the desired scale, they perceive
that it is impossible. In some of these cases the user may reach the conclusion that the
maximum scale that can be reached for the product in terms of geometry can be very
different from the maximum scale reached in terms of information contents available in that
product. However, in other cases it is also possible that the user does not even perceive such
difference and will end up making inappropriate use of that data.
The authors have no intention to criticize the performance of assessments regarding only
accuracy. Actually, what we have been doing mostly, in a systematic way, is this type of
assessment. The interest lies in calling attention for the need to complement the assessments
with considerations regarding accuracy of the represented contents. As the existence of a
critical mass regarding the need for assessments for accuracy of geometry is already
perceived, it is desired to create a demand for investigations regarding the contents of what
is represented.
As an example of such duality in the assessment of accuracy for the case of orbital images,
we can mention the ALOS/PRISM in [16] planialtimetric data assessment report and in [19]
on planimetric assessment of AVNIR2 images. Both texts present the maximum scales in
terms of planialtimetric and planimetric accuracy, respectively, mentioning that the
products may not allow the extraction of elements in the same scale. In order to know this
last information it would be necessary to carry out an assessment of the images
interpretability.
It is also important, to minimize the intensity of a statement - which is sometimes
mentioned - that for thematic cartography, geometry may be neglected, while for reference
cartography geometry is all that matters. Due to this, many thematic maps present serious
geometry problems, which makes them incompatible for the foreseen scale, likewise as in
reference cartography one may find maps - often adjacent to each other - that present
different information densities, or even, a lack of standardization of what is being
represented.
It is necessary to think about the problem, to suggest solutions and create a form of
assessment that is really viable for the use by several producers of cartographic data -
whether referential or thematic, whether originated from official mapping agencies or
private companies, research groups, etc. who handle these types of data. What matters is to
invest in the proposition of standards for assessment of such data. These standards should
be appropriate for the new techniques for data acquisition and handling, considering the
digital context and dealing with accuracy in terms of geometry and contents.
When we consider the use of remote sensing data - whether originated from aerial or orbital
levels - a set of cares is necessary, starting with the appropriate sensor choice, the time of the
year for data acquisition, but treatment of the data and extraction of the desired information.
People often say that the only optimal solution is the one obtained through
photogrammetric survey. And for many applications it really is the best. But a survey
carried out in the scale and dates desired is not always available. And for other applications
