249
5 DSM is a digital elevation model in raster format. Each cell of the model, called pixel,
holds a height number. Therefore, DSM represents the spatial distribution of the dimensions of an area or surface.
point cloud created with the Dense Image Matching (DIM) method has a
much lower cost, making it more accessible to Public Administrations.
To assess the solar incidence impacting the slopes of buildings and horizontal urban surfaces, we trace a methodology composed of three steps.
Step One
In order to transform the point cloud generated by the stereoscopic technique,
the first step is to transform it into a DSM
5 (Digital Surface Model), which is
a raster file whose pixels contain the average dimensions of the points of
the cloud.
The very high density of the cloud has allowed us to create a DSM with a
0.5 m
2 per pixel resolution. The conversion can take place with the aid of various software tools; for the prototype we used LAStolls. This application has a
very simple command line interface, developed by Martin Isenburg for
LiDAR data, but which could be used for this specific operation on photogrammetric data in the LAS format.
The command for the operation is the following:
las2dem -i name_file_input.las -o name_file_output.tif -step 0.5
By using this command on Command Prompt, the software automatically
transforms the point cloud into the desired DSM.
Step Two
The second step consists in producing information pertaining to solar incidence and the inclination angles of roof slopes. This operation was performed
with the Open Source Software System for Automated Geoscientific Analyses
(SAGA GIS). SAGA GIS has many algorithms, one of which can calculate
the inclination angles of surfaces (by Olaya 2004), and another the potential
solar incidence of surfaces (by Conrad 2010).
The information layer pertaining to the inclination angles of roof slopes
will be crucial in the classification of roofs, as for the study in question it is
important to distinguish flat roofs from sloping roofs. The inclination angles
of roofs are also essential in selecting and suggesting an installation type.
(continued)
8 Mitigation of and Adaptation to UHI Phenomena: The Padua Case Study
5 DSM is a digital elevation model in raster format. Each cell of the model, called pixel,
holds a height number. Therefore, DSM represents the spatial distribution of the dimensions of an area or surface.
point cloud created with the Dense Image Matching (DIM) method has a
much lower cost, making it more accessible to Public Administrations.
To assess the solar incidence impacting the slopes of buildings and horizontal urban surfaces, we trace a methodology composed of three steps.
Step One
In order to transform the point cloud generated by the stereoscopic technique,
the first step is to transform it into a DSM
5 (Digital Surface Model), which is
a raster file whose pixels contain the average dimensions of the points of
the cloud.
The very high density of the cloud has allowed us to create a DSM with a
0.5 m
2 per pixel resolution. The conversion can take place with the aid of various software tools; for the prototype we used LAStolls. This application has a
very simple command line interface, developed by Martin Isenburg for
LiDAR data, but which could be used for this specific operation on photogrammetric data in the LAS format.
The command for the operation is the following:
las2dem -i name_file_input.las -o name_file_output.tif -step 0.5
By using this command on Command Prompt, the software automatically
transforms the point cloud into the desired DSM.
Step Two
The second step consists in producing information pertaining to solar incidence and the inclination angles of roof slopes. This operation was performed
with the Open Source Software System for Automated Geoscientific Analyses
(SAGA GIS). SAGA GIS has many algorithms, one of which can calculate
the inclination angles of surfaces (by Olaya 2004), and another the potential
solar incidence of surfaces (by Conrad 2010).
The information layer pertaining to the inclination angles of roof slopes
will be crucial in the classification of roofs, as for the study in question it is
important to distinguish flat roofs from sloping roofs. The inclination angles
of roofs are also essential in selecting and suggesting an installation type.
(continued)
8 Mitigation of and Adaptation to UHI Phenomena: The Padua Case Study