The Department has
been producing orthophotographs for 10 years. Moreover, the Department has
developed sound expertise in playing a key role during special projects
for managing risks related to landslides and flooding. This expertise
in orthophotograph production and aerotriangulation, which is made
available to public-sector agencies and departments of the gouvernement du Québec, covers the following:
- Defining the product appropriate to the customer's needs (scale,
digitalization, digital elevation model, georeferencing, and digital
- Planning work;
- Writing technical specifications;
- Awarding and supervising contracts;
- Quality control.
In 1992, the Department began orthophotograph production
in order to improve quality control for the Base de données
topographiques du Québec at the 1:20,000 scale.
This was carried out using photographs at the 1:40,000 scale,
digitized at high resolution. They were corrected and rectified
with respect to the earth in order to eliminate in accuracy due
to tilt displacement due to camera angle and image displacement
due to relief. The parameters for calibrating the airborne camera,
aerotriangulation coordinates, and digital elevation model are used
to carry out orthorectification.
Nearly 4,000 orthophotos at the 1:40,000 scale
(of 1 metre resolution), covering all the habited portion
of Québec, are available.
Areas of Application
Halfway between a map and aerial photography, an
orthophoto offers the detail and richness of an aerial photograph
combined with the accuracy of a map. Since orthophotos are georeferenced,
they can include geographic information or bring out topography,
territory boundaries, and themes related to various sectors of activity.
Orthophotography can be used in a number
of fields, including:
- The environment;
- Civil engineering;
- Urban planning.
The homogeneity and quality
of work are provided for through the application of rigorous
standards. Projects managed by Department are carried out by
specialized Québec firms, many of which have already worked abroad,
in particular in Africa, Central America, and South America.
The Department has significant expertise
in producing digital orthophotos. This recognized know-how can be
shared with any government concerned with optimally developing its