Indigenous Burial Site Surveys
Recent events in Canada have brought the use of Ground Penetrating Radar (GPR) for the purpose of locating potential unmarked burial sites of indigenous people particularly at former residential schools to the forefront of public attention.
Terraprobe has been conducting subsurface GPR surveys since 2001 including many ancient burial site projects. This type of project is challenging and requires the right equipment and experienced personnel to design the survey and interpret the collected data correctly.
Terraprobe staff would be pleased to consult with you about your project to ensure that you understand GPR capabilities and the details surrounding a search for unmarked burial sites.
Subsurface investigation using the Stream-C Array in southern BC.
Possible ancient burial site survey done with no visual indicators. The only evidence was oral history. The site was in northern BC.
Survey near Hwy 1 in Fraser Canyon to locate possible burial sites from 1800's using a single antenna system.
Sample GPR data from city cemetery using Stream -C array.
Sample Single line GPR Data of marked and unmarked graves. This is unprocessed data.
Marked and Unmarked indigenous site report example.
Indigenous Burial Site Investigations
- Ground penetrating radar survey is one method used in archaeological geophysics. GPR can be used to detect and map subsurface archaeological artifacts, features, and patterning. The concept of radar is familiar to most people. With ground penetrating radar, the radar signal – an electromagnetic pulse – is directed into the ground. Subsurface objects and stratigraphy (layering) will cause reflections that are picked up by a receiver. Data may be plotted as profiles, as planview maps isolating specific depths, or as three-dimensional models. GPR can be a powerful tool in favorable conditions (uniform sandy soils are ideal). Like other geophysical methods used in archaeology (and unlike excavation) it can locate artifacts and map features without any risk of damaging them. Among methods used in archaeological geophysics, it is unique both in its ability to detect some small objects at relatively great depths, and in its ability to distinguish the depth of anomaly sources. The principal disadvantage of GPR is that it is severely limited by less-than-ideal environmental conditions. Fine-grained sediments (clays and silts) are often problematic because their high electrical conductivity causes loss of signal strength; rocky or heterogeneous sediments scatter the GPR signal, weakening the useful signal while increasing extraneous noise.
The Equipment We Use
Terraprobe uses some of the most advanced radar systems available for this type of work.
To complete a successful survey of an area where the location of burial sites are unknown, data collection needs to be done in a grid pattern and the data processed offsite using software designed for this purpose. The experience of the technician is very important as the software requires input from the technician which is interpretive in nature.
The equipment we employ is divided into two categories: Single or Dual antenna systems, and Multi-Antenna Array systems.
When using a single antenna system, data must be collected in a grid pattern. Grids are set-up on the ground being surveyed and the system is moved over the ground on lines typically spaced 25cm apart.
When using a multi-antennas array system, the data is collected on 1.5 meter spacing in a single direction but the effective data spacing is 5cm. This method essentially provides 100% coverage of the scanned area.
Multi antenna array systems allow for greater detail in data collection with much shorter data collection times.
Our systems are also GPS capable which allows us to conduct data collection without manually setting up grid patterns to follow and facilitates identification of detected sites with GPS coordinates.
Stream C Multi -Antenna array system. Thirty four (34) antennas oriented in 2 polarizations.
IDS 4Lite dual antenna system with 200 MHz and 600 MHz antennas.
The Process We Use
Terraprobe uses the correct radar system and methodology for each survey we conduct - including the Stream-C multi-antenna array system from IDS - the most advanced Ground Penetrating Radar system for sub-surface surveys available today.
Burial Site Locate Methodology
Standard Single or Dual Antenna GPR Systems.
• When using a single or dual antenna radar system the site survey is conducted using a grid method for data collection. Generally the grid spacing is set at 25cm in order to capture small targets.
• The collected data is then processed using software designed to collate the data and aid the technician in interpreting the results. The software requires input from a GPR specialist experienced in understanding GPR data analysis for this application.
The single antenna systems are also useful in areas with rougher terrain.
Multi-Antenna Array System
• The Stream- C radar system has a massive array of 34 antennas in two polarizations: This allows for data to be collected in a single direction with effective 5cm line spacing and avoid the time taken for grid setup and two direction radar scans.
• The collected data is processed and a report showing potential burial locations is produced.
• The system can be used manually or towed with a small vehicle, increasing the acquisiton speed (up to 6 km/h).
• The Stream-C allows for fast data collection over large areas reducing field time by at least 50% over single or dual system grid methodology.
The GPR data is processed and interpreted to determine the location of anomalies that are likely to be burial locations. This information is then overlaid on a drawing of the the property in question. Terraprobe can also conduct an aerial site survey to produce a photogrammetric map on which the GPR data is overlaid.