Blog 2020

Open-Pit Mine Engineering-grade Mapping:
Satellite Mapping vs Drone Mapping

Keywords: Open-Pit Mines; Drone Mapping; Satellite Mapping | October 2020--------------------------------------------------------------------------------------------------------------------

Both Satellite and Drone Optical Imagery are recurrently used to produce 3D models and OrthoPhoto Maps of open-pit mines.

Recurrent mapping allows site managers to track tailings and overburden volumes and location, as well as mine pit geometry.

Satellite Mapping has been mostly based on the photogrammetric processing of very-high-resolution, stereo optical imagery.

Drone Mapping has also been mostly based on optical imagery (but with structure-from-motion algorithms). While a few satellite images may cover an entire mine site, 100s or 1000s of Drone photos may be needed to cover a large mine.

Advantages of Satellite Mapping over Drone Mapping include:

  • A small number of images covers entire mine sites.

  • No field work is necessary other than for establishing ground control.

  • Only a relatively small number of ground control points is necessary.

Disadvantages of Satellite Mapping over Drone Mapping include:

  • Satellite imaging is not possible in overcast conditions.

  • 3D model resolution may not be sufficient to map and measure certain features.

  • Satellite tasking may not always be possible for the desired dates.

Drone Mapping is more versatile and produces more detailed 3D models than Satellite Mapping. Additionally, a number of Drone platforms have engineering-grade Differential Positioning, reducing or eliminating the need for other ground control.

Lightweight LiDAR platforms are revolutionizing Drone-base topographic mapping, but arenโ€™t necessarily advantageous for bare-ground areas such as Open-Pit Mines: slower flight speeds; typically require lower flight elevations and thus longer mission time; costly.

In remote areas, where access to Drone services is difficult, Satellite Mapping may be the best option for Open-Pit Repeat Mapping. But where Drone Services are available, these are likely more cost-effective and will lead to more detailed deliverables than satellite data. Liability of ground work can be reduced by shifting flights to weekends and holidays.

At XYINTEL we provide both Satellite-based and Drone-based mapping of Open-Pit Mines throughout the year.

Drones: Applications in Forestry

Keywords: Forestry; Drones; UAV; Cutblock; Drone Mapping; British Columbia | October 2020------------------------------------------------------------------------------------------------------------------------

Unmanned Aerial Vehicles, or Drones, have become inexpensive tools for not only high quality aerial video and photography, but also spectral and topographic mapping.

Drones have become ubiquitous tools in the Natural Resources Industry.

Applications in forest harvesting can be grouped into pre-harvest applications and post-harvest applications.

Figure 1. Upper panels: Pre-harvest forest Stands; Lower panels: Post-harvest.

Orthophotos (aerial imagery) from reconaissance flights reveal details that are not possible to discern from the ground. Additionally, Drones quickly cover areas that would take days more to cover on foot.

The best forest stands can be identified from Drone aerial orthophotos. This optimizes the process of selecting locations for new cutblocks which to apply for.

During cutblock layout (where to cut, where to preserve), those same orthophotos can help pre-determining areas to partial out, such as due to wildlife reasons or forest stand composition.

Additionally, we have had ground crews (e.g., bunchers) mentioning that real-time georeferenced access to a detailed top-down view of the trees is of great help as they progress through the cutblock.

Legally-binding site plans are necessary and determine where harvest is to take place, but often do not include recent and detailed aerial imagery. But there is no reason to not include that kind of information, if available, into a site plan or a relativity lean logging plan.

Post harvest aerial photo-mosaics address one important component of licensees obligations: report to the government what was done relative to what had been planned. Post-harvest aerial photomosaics can be used for a detailed mapping of the post-harvest cutblock area.

Drones are also increasingly used for stock imaging and volume estimation purposes in lumber mills in general, pellet plants, biomass plants, etc.

Many companies are developing new applications. It is likely that Drones will be systematically used in the near future for silvicultural activities such as tree planting, at least in certain environments.

Forect Cutblock Drone Mapping

Keywords: Forestry; Post-harvest; Mapping ; UAV; Drone; British Columbia | Sept 2020--------------------------------------------------------------------------------------------------------------

Figure 1. Left panel: Digital Surface model derived from Drone Overlapping Photos. Right panel: Orthophoto.

At a time when softwood lumber prices have reached all- time highs, high resolution Drone mapping of cutblocks

1) prior to logging,
2) and as the disturbance progresses

can help ground crews manage and optimize resource allocation.

Figure 1. Left panel: Drone Orthophoto. Right panel: Estimation of vegetation height from Drone Photogrammetric Point Cloud.

Additionally, point clouds from the photogrammetric processing of Drone Overlapping Photos can be used to derive coarse maps of vegetation height. In conjunction with the Orthophoto, that information is useful for determining field work locations for layout and reconnaissance cruising, prior to heading to the field.

British Columbia:
COVID-19 outlier among Canada's most populous provinces

Keywords: COVID-19; confirmed cases per capita; Canada ; British Columbia | July 2020----------------------------------------------------------------------------------------------------------------

Figure 1. Total number of per-capita (per 1000 people) COVID-19 infections across Canada. Provinces and Territories are listed by increasing population.

Among the four most populous provinces in Canada, British Columbia stands out for a relatively low number of COVID-19 confirmed-cases per capita (per 1000 people in the plot).

For example, British Columbia has 40% less population, but 9x less COVID-19 confirmed-cases per capita, than Quebec.

While more populous regions or countries can generally be expected to have more people infected by COVID-19, there are many complicating factors.

Geographically, it is important to also consider:

- spatial autocorrelation: the closer a region is to another region with a high number of infections, the more likely it is to have a higher number of infections;

- connectivity and flow of humans: areas that receive more visitors or serve as transportation hubs for multiple regions are more likely to import active cases;

- population density, due to the reliance of the spread of the virus on the proximity between humans (community transmission).

Understanding the spatial disparities between countries and regions will require looking at:

- strictly spatial determinants

- health-system response and capacity

- population general health

- preventive measure adoption

- movement of people during the pandemic

- specific events that may have acted as catalysts, fundamentally affecting the evolution of the spread

๐˜พ๐™ค๐™–๐™จ๐™ฉ๐™–๐™ก ๐™‚๐™–๐™จ๐™‡๐™ž๐™ฃ๐™ : ๐™‹๐™ง๐™ค๐™œ๐™ง๐™š๐™จ๐™จ ๐™—๐™š๐™ฉ๐™ฌ๐™š๐™š๐™ฃ ๐˜ฝ๐™ช๐™ง๐™ฃ๐™จ ๐™‡๐™–๐™ ๐™š ๐™–๐™ฃ๐™™ ๐™ƒ๐™ค๐™ช๐™จ๐™ฉ๐™ค๐™ฃ, ๐˜ฝ๐˜พ

Keywords: satellite mapping; Coastal GasLink pipeline ; natural resources; engineering project tracking--------------------------------------------------------------------------------------------------------------------------------

Figure 1. Coastal GasLink Natural Gas pipeline license and actual route between the longitudes of Burns Lake and Houston: status on May 2020. Background: Sentinel-2; ALOS DEM

The Coastal GasLink pipeline will transport Natural Gas westwards, from the Dawson Creek area to Kitimat, where it will be liquefied for exporting.

Until about 20 km west of Tchesinkut Lake, the developed pipeline route closely followed the area of the respective Crown License active on May 2020.

Twenty kilometres west of Tchesinkut Lake, the pipeline turned south from the planned route.

That deviation from the planned route is likely related to the dispute with the Office of the Wet'suwet'en Hereditary Chiefs.

By May 2020, the western end of the developed pipeline route was located to the north of Parrot Lakes. This is approximately at the longitude of Houston, BC.

Recurrent mapping based on satellite imagery with high temporal resolution provides the opportunity to closely follow the progress of large engineering projects on public lands.

๐™‹๐™ค๐™จ๐™ฉ-๐™ƒ๐™–๐™ง๐™ซ๐™š๐™จ๐™ฉ ๐˜พ๐™ช๐™ฉ๐™—๐™ก๐™ค๐™˜๐™  ๐™๐™ค๐™ง๐™š๐™จ๐™ฉ ๐˜พ๐™ค๐™ซ๐™š๐™ง ๐™ˆ๐™–๐™ฅ๐™ฅ๐™ž๐™ฃ๐™œ ๐™›๐™ง๐™ค๐™ข ๐™Ž๐™–๐™ฉ๐™š๐™ก๐™ก๐™ž๐™ฉ๐™š ๐™„๐™ข๐™–๐™œ๐™š๐™ง๐™ฎ

Keywords: satellite mapping; forestry mapping; British Columbia; Forest Cover RESULTS submissions; natural resources------------------------------------------------------------------------------------------------------------------------------------------------------

Figure 1. Forest cover mapping based on a satellite image of a cutblock in the Nechako-Bulkley region of British Columbia, Canada

There is a large number of Earth imaging satellites with high to very-high resolution cameras.

The cell-size of their images generally ranges between 30 cm and 1 m . This is sufficient to map the smallest features in a cutblock.

Combining all the different satellites, an area is often imaged multiple times per year. This is specially important for post-harvest forest cover mapping.

Across resellers, the pricing of archive imagery is generally around USD 14-20 per square km. There is a minimum order: 25 sq. km.

Satellite imagery is cost-effective relative to Drone mapping. The latter requires field work. This is time consuming:

  • It takes time to get to the cutblocks; and,

  • if flown at legal altitudes, Drones may need more than one day to cover large blocks.

Additionally, once in the office, the Drone photos need to be processed into a seamless mosaic. This may need ancillary information for satisfactory positional accuracy.

XYINTEL is an approved reseller for same satellites and has also specialized in post-harvest mapping and RESULTS reporting.

2018 ๐™๐™ž๐™ง๐™š๐™จ ๐™Ž๐™ค๐™ช๐™ฉ๐™ ๐™ค๐™› ๐˜ฝ๐™ช๐™ง๐™ฃ๐™จ ๐™‡๐™–๐™ ๐™š: ๐™จ๐™–๐™ฉ๐™š๐™ก๐™ก๐™ž๐™ฉ๐™š ๐™ž๐™ข๐™–๐™œ๐™š ๐™จ๐™๐™ค๐™ฌ๐™จ ๐™– ๐™›๐™ž๐™ง๐™š ๐™จ๐™ฉ๐™–๐™ง๐™ฉ๐™ž๐™ฃ๐™œ ๐™ก๐™ค๐™˜๐™–๐™ฉ๐™ž๐™ค๐™ฃ

Keywords: satellite mapping; forestry mapping; post-fire mapping; 2018 fires; British Columbia; northern BC---------------------------------------------------------------------------------------------------------------------------------------

Figure 1. Sentinel-2 image from July 31, 2018

The year 2018 was marked by large fires in interior British Columbia.

Those fires affected some 60,000 ha of land south of Burns Lake, between the Nechako Reservoir and Franรงois Lake.

Figure 1 is a Sentinel-2 image from July 31, where a likely fire initiation point is visible.

In that true-color image, a white smoke column is seen just to the north of Cheslatta Lake. The fire is thought to have been triggered by lightning.

Figure 2. Sentinel-2 image from September 29, 2019

Figure 2 is an image from the Summer of 2019. It shows dramatic changes in land cover relative to pre-fire conditions.

The colors are not directly comparable between the two satellite images; but the boundary between burnt and intact areas is obvious in places, particularly south of Cheslatta Lake.

Another interesting aspect is that even harvested cutblocks that look sterile in the pre-fire image, look burnt in the post-fire image. Indeed, post-fire replanting is often necessary.

British Columbia's FRPA section 108 contemplates funding for post-fire replanting when establishing a free growing stand requires significant extra expense.

XYINTEL has mapped cutblocks and made many RESULTS Forest Cover submissions to meet s.108 requirements on behalf of clients.

๐™ˆ๐™ž๐™˜๐™ง๐™ค-๐™จ๐™–๐™ฉ๐™š๐™ก๐™ก๐™ž๐™ฉ๐™š ๐™˜๐™ค๐™ฃ๐™จ๐™ฉ๐™š๐™ก๐™ก๐™–๐™ฉ๐™ž๐™ค๐™ฃ๐™จ: ๐™ช๐™จ๐™š ๐™ž๐™ฃ ๐™๐™ค๐™ง๐™š๐™จ๐™ฉ๐™ง๐™ฎ

Keywords: micro-satellite mapping; forestry mapping; cutblock mapping; British Columbia; central British Columbia-------------------------------------------------------------------------------------------------------------------------------------------------

Figure 1. False-color view of cutblock in Central British Columbia [PlanetScope, PlanetLabs image].

Micro or miniaturized satellites are smaller than one cubic foot and weigh around 1kg.

Very large constellations of micro satellites have the capacity to image the entire Earth very frequently (daily).

The PlanetScope Dove micro-satellite constellation, for example, provides optical imagery between 3 m and 4 m in ground sampling distance (distance between image pixels/cells).

That resolution is smaller than that of the most recent SPOT satellites (1.5 m panchromatic band) but is significantly better than the imagery from Sentinel-2 (10 m panchromatic band).

The imagery from micro-satellite constellations generally costs a few U.S. dollars per sq. km. That is significantly cheaper than the data from higher resolution satellites such as SPOT and WorldView. Very-high-resolution satellite imagery typically costs USD10-17 per sq. km for base products. Additionally, the temporal resolution of very high resolution satellites such as WorldView-3 may translate into only a few images per year for a certain area.

Is micro-satellite imagery useful for post-harvest cutblock forest cover mapping?

Figure-1 displays portion of a cutblock just to the north of Cheslatta Lake, in Central B.C., Canada. The pink tones generally reflect bare-ground and areas logged a year or so ago; the dark greens indicate mature forest; and the bright greens are associated with short vegetation. Grayish to brownish tones were logged recently.

Positive traits for post-logging cutblock forest cover mapping:

1) on-block roads are generally sharply differentiated;

2) positional accuracy of orthorectified imagery is acceptable.

Limitations for post-logging cutblock forest cover mapping:

1) while large vegetation patches are generally visible, the boundary of smaller occurrences is difficult to discern;

3) while the newly harvest area can generally be identified in grey-to-brown tones, a detailed definition is complicated by a mixing with fuzzy patches of other land covers.

Therefore, it appears that this type of medium-high resolution imagery is not able to support a detailed forest cover mapping.

What about other uses in forestry?

Among other potential uses, the combined medium-high resolution, daily revisitation time of this type of imagery may be useful for:

1) providing rapid information for natural hazard response, management , and monitoring, particularly in remote regions;

2) supporting compliance tracking for tenured operations in Public/Crown forest management area;

3) potentially, identify other illegal activies in Public/Crown forest.