The LIDAR instrument used for SLC Project Phase 1 was a Faro Focus 3D from
Bishop’s University, capable of capturing a maximum of 960,000 points per second. LIDAR
instruments work by emitting a laser at ~900 nanometers and recording the return time of the
signal, in order to determine the distance between the instrument and the corresponding
surface. A multitude of these data points are combined to create a high-resolution,
three-dimensional image of the instruments surroundings and in this case, the regions the SLC.
LIDAR imaging may be used in GIS to create detailed maps in forestry and various other
divisions of geospatial studies, and multiple scans may be taken in order to monitor physical
changes over time. The purpose of using LIDAR imaging in the SLC Project was for the
construction of a three-dimensional, digital representation of the SLC regions that are not open
to the public at this time. Reconstruction of this model requires the integration of multiple overlapping LIDAR
scans using GIS computer software, and the integration of separate scans into one image may
be done by connecting common reference points between multiple images to properly reference
important features. Targets were constructed for this purpose using styrofoam balls and printed
grids, which were anchored in SLC walls with a magnetic connection between each target and a
nail which was embedded in the cavern wall. Scan quality settings on the LIDAR instrument
were manipulated to increase efficiency in practice sessions at Bishop’s University before the
first excursion, and during the initial imaging at the SLC.
The first expedition of the SLC Project took place on January 29th and included all members of the ESG 362 class, lead by Professor Bruno Courtemanche. The main objectives of the first excursion were to take LIDAR scans of the public and private sections of the SLC, test the hypothesis of Professor Courtemanche regarding the presence of fluorescent organisms on SLC walls, and view sections of the SLC using a thermal imaging tool. Our group worked with the ultimate intention of creating a complete three-dimensional reconstruction of the accessible SLC areas, which was to be published digitally. Instruments and lights were powered using a combustion generator situated outside of the SLC, with extension cables running to the furthest accessible regions of the SLC. Approximately five members of the group at a time conducted analyses in the SLC’s lowest section, while additional group members worked on tasks in the public section of the SLC and elsewhere on the park premises.
Black Light Analysis:
A black light was used to illuminate parts of the SLC walls at a narrow wavelength, in
order to reveal fluorescent organisms or substances. Ultraviolet light is classified as that which
emits radiation between 400 and 10 nanometers, between visible light and X-rays on the
electromagnetic spectrum. Conventional black lights such as the one used in Phase 1 of the
SLC Project emit long-wave UV (ultraviolet) radiation that has a wavelength from ~400
nanometers to slightly less than this (just beyond the visible spectrum of light). Fluorescent
organisms and substances are capable of re-emitting ultraviolet radiation at different wavelength in the visible spectrum, and as result become bright and clearly visible under unpolluted ‘black light’.
The black light analysis performed during the first trip confirms the presence of
fluorescent organisms in the SLC, and despite not being a central goal in the SLC Project,
constitutes further research. The stability of the SLC remains questionable, and the extent of the
recently discovered section of the SLC remains largely unknown. The extent of the SLC
currently appears vast, but the full extent of the caverns and their correspondence with surface
features is uncertain at this time. Seasonal variability of the cavern’s water table and its
implications for the ongoing study of the SLC is also an area of limited understanding. Early
results of the LIDAR scan reconstruction using GIS software show promise in creating a
detailed digital model of the SLC.