Details: Aeroquest Airborne conducted a helicopter-borne magnetic survey on Block 1; and Geo Data Solutions GDS Inc. conducted helicopter-borne magnetic surveys on Blocks 2 and 3 of the QUEST-Northwest project area for Geoscience BC (GBC).
Block 1: between the communities of Dease Lake and Iskut, BC in the summer and fall of 2011. This airborne magnetic survey was flown by Aeroquest Airborne with a line spacing of 250 m, and the total survey coverage is 27,012 line-km.
Block 2: near the community of Telegraph Creek, BC in the summer and fall of 2011. This airborne magnetic survey was flown by Geo Data Solutions with a line spacing of 250 m, and the total survey coverage is 11,345 line-km.
Block 3: located near the community of Iskut, BC in July and August of 2012. This high-definition heliborne survey was flown by Geo Data Solutions with a line spacing of 250 m, and the total survey coverage is 5746 line-km. The report also includes 200 line-km of airborne magnetic data purchased from New Chris Minerals Ltd. This dataset was collected in late 2011 and early 2012 at a 100 m line-spacing, and lies in the centre of the Block 3 area.
These surveys are all part of Geoscience BC’s QUEST (QUesnellia Exploration STrategy Project).
Survey Background for Block 1 - between Dease Lake and Iskut (GBCR 2012-02): The aeromagnetic survey was carried out by Aeroquest Airborne using an A-star 350B2 helicopter with a stinger mounted cesium vapor magnetometer. The magnetometer was a Geometrics G823 A, with a sample rate of 10Hz and sensitivity of 0.01 nT.
The survey operations were carried out from August 13th 2011 to October 28th, 2011. The total survey coverage
is 27,012.22 km. Sensor height was a smooth drape of 80 metres but was periodically higher or lower due to the rugged terrain and the capacity of the aircraft. The scan rate of the helicopter stinger data acquisition was 0.10 seconds. It was controlled by a computer assisted, real-time corrected Global Positioning System, which provided vertical, as well as horizontal guidance. Using a video overlay board the GPS time is recorded continuously and is displayed on the margin of each image. This procedure ensures accurate correlation of digital data with respect to visible features on the ground. Navigation is carried out using a GPS receiver, an AGNAV GUIA system for navigation control, and AeraDAS data acquisition system which records the GPS coordinates. The x-y-z position of the aircraft, as reported by the GPS, is recorded at 0.2 second intervals. The system has a published accuracy of less than 3 metres. A recent static ground test of the Mid-Tech WAAS GPS yielded a standard deviation in x and y of less than 0.6 metres and for z less than 1.5 metres over a two-hour period.
The geophysical maps accompanying this report are based on positioning in the NAD83 datum. The survey geodetic GPS positions have been projected using the Universal Transverse Mercator projection in Zone 09 North. Test lines were flown to check the real time magnetic compensation in four cardinal directions corresponding to the survey line direction. The compensation test was carried out near Dease Lake and flown approximately 10,000 ft AGL to ensure the sensor was completely removed from ground effect.
The total field aeromagnetic data are corrected for the diurnal variation, by subtracting the base station magnetic data (low pass filtered to remove spikes due to cultural interference). Then the line data was corrected for any remaining small levelling errors. The geophysical data are interpolated onto a regular grid using bi-directional interpolation technique. The gridded data was micro-levelled to remove small amplitude, in between flight line, levelling errors. The resulting grid is suitable for generating contour maps of excellent quality.
The report includes a set of 1:50,000 scale hardcopy maps. The survey area is covered by one map plate and two geophysical data products are delivered as listed below:
TMI – Coloured Total Magnetic Intensity (TMI) with contours.
1VG – Calculated First Vertical Derivative of TMI colour grid with contours.
The coordinate/projection system for the maps is NAD83 – UTM Zone 09N. For reference, the latitude and longitude in WGS84 are noted on the maps.
The geophysical profile data is archived digitally in Geosoft GDB binary database format. Levelled Grid products used to generate the geophysical map images.
View QUEST Northwest Block 1 Project Area Map
Survey Background for Block 2 - near Telegraph Creek (GBCR 2012-03):
The aeromagnetic survey was carried out by Geo Data Solutions GDS Inc. (GDS) using an A-star 350B2 helicopter with a stinger mounted cesium vapor magnetometer near Telegraph Creek, B.C. The magnetometer was a Geometrics Cesium split-beam magnetic sensor, with a sample rate of 10Hz and sensitivity of 0.01 nT and resolution better than 0.025 nT per measurement.
The survey operations were carried out in the summer and fall of 2011. Nominal traverse and control line spacing were 250 m and 2 500 m respectively and the aircraft nominal terrain clearance was 80 m. The survey was flown on a pre-determined flight surface in order to minimize differences in magnetic values at the intersections of control and traverse lines. These differences were computer-analysed to obtain a mutually levelled set of flight-line magnetic data.
View QUEST Northwest Block 2 Project Area Map
Survey Background for Block 3 - near Iskut (GBCR 2013-03):
The aeromagnetic survey was carried out by Geo Data Solutions GDS Inc. (GDS) using an A-star 350B2 helicopter with a stinger mounted cesium vapor magnetometer near Iskut, B.C. The magnetometer was a Geometrics Cesium split-beam magnetic sensor, with a sample rate of 10Hz and sensitivity of 0.01 nT and resolution better than 0.025 nT per measurement.
The survey operations were carried out from July 27th to August 6th, 2012. 18 production flights were needed to
cover the requested areas. The Infill traverse were flown over the previously New Chris Minerals Ltd survey flown by SkyTEM and Aeroquest in 2011 and 2012 in order to complete these surveys. The Infill Traverses were levelled and a new grid (using Gridbool, from Geosoft) was created with the New Chris Minerals Ltd. data in December 2012 and January 2013. Sensor height was a smooth drape of 80 metres but was periodically higher or lower due to the rugged terrain and the capacity of the aircraft. Navigation is carried out using a GPS receiver, model Novatel DL-V3 Dual-freq L1/L2. Post-flight differential correction of the raw GPS data was done using the Natural Resources Canada online GPS processing service CRSR-PPP (Canadian Spatial Reference System - Precise Point Positioning).
GDS produced three copies of a CD-ROM containing digital archives and maps (PDF and Geotiff formats). Digital archives contain the Geosoft database of all survey data. The database is referenced to the standard UTM co-ordinates for the area.
A Block 3 grid (cell: 62.5m) and an infill grid (cell: 25m) named “New Chris” were produced. Base maps with information from published topographic maps was produced at a scale of 1:50 000 show flight paths and UTM coordinates. Three paper copies of shaded residual total magnetic field and shaded magnetic first vertical derivative are available. All final map products were also delivered in PDF and Geotiff formats at resolution suitable to accurately reproduce plotted products.
Free viewing software are Geosoft Oasis Montaj Viewing Software and Adobe Acrobat Reader.
View QUEST Northwest Block 3 Project Area Map