Studying the degree of granite alteration using open spatial data platforms. Case studies: Guarda urban area and Estrela Geopark

Abstract

The continuous reorganization of the territory, whether due to the
appearance of new buildings or to the alteration and reformulation
of the existing space, requires updated cartographic information.
This update is intended to represent the present situation, and the
various updates allow us to obtain a territorial history of recognized
importance.
In geotechnical cartography, the urban reorganization that includes
excavations, foundations, trenching, wells and boreholes, etc., allows
the collection of information that constitutes a large collection of
data. This territorial reorganization is more urgent in urban areas,
however, in rural and natural areas of great geological emphasis,
the existence of rocky outcrops and the possibility of identifying
and analyzing these rocky outcrops is also of great importance for
geotechnical cartography.
The present study analyzes the use of spatial data infrastructures
from the free Street View - Google Maps platform, which, duly incorporated
in open-source free software (QGIS), allows the elaboration
of geotechnical cartography in urban and rural areas.
The case studies presented here refer to the urban area of the city
of Guarda and to the rural zone defined as Estrela Geopark (Estrela
Mountain), in which granite areas are identified through modules
with connection to Google Street View and where the degree of
granite alteration is analyzed. The validation of the degree of alteration
of the granite is later verified through in-situ observations to
validate the assigned classification. Through this methodology and
in an expeditious way, it is possible to create geotechnical cartography
and the respective database with relevant and complementary
information to the existing geological cartography.