## 4 Results
### Shoreline Extraction  
Figure 9a presents the main Mackenzie River channel as well as tributary areas derived from the satellite imagery, overlaid on the Spotlight RADARSAT-2 image for reference. The dark areas adjacent to the main channel, which flood periodically, represent drying areas. To identify changes in the river's position since the last update of chart 6428 in 2011, a vector of the river was overlaid on a georeferenced version of the chart (Figure 9b). By comparing the current position of the river to the position illustrated on the chart, areas of change could easily be identified, providing a reference of where changes to the chart should be made. Changes in the path of the river relative to chart 6428 are visible in Figure 9b. This figure illustrates that the position of almost all portions of the river's channel and tributaries have changed since chart 6428 was produced. This is particularly evident in the meander of the river situated just south of Raymond Channel (see white and black arrows within Figure 9a,b, respectively). At this location the full width of the river currently passes through an area  
Figure 8: Simulated RCM RH (**a**), RR (**b**) (8 October 2014) and RH (**c**), RR (**d**) (7 September 2016) images acquired over the study area. The red arrows point to mud-flat areas in RH and RR in calm and windy conditions.  
Figure 7: Land-water contrast in RH and RR polarizations.  
of land indicated on the chart. At other locations, the recommended track shown on the chart passes through areas which are currently land. For a considerable amount of the examined area, the current chart cannot accurately be used for navigational purposes, requiring mariners to rely entirely on their judgement and aids to navigation for safely navigating these sections of the Mackenzie River.  
Figure 10 displays an example of segmentation and classification results from a combination of Landsat data retrieved in July 2017, and RADARSAT-2 data acquired at low water level in October 2017. The Landsat imagery represents what would be visible to a navigator during navigation season (Figure 10a, upper image) therefore these areas are mapped as land features. The low water level areas from the RADARSAT-2 imagery (Figure 10a, lower image) characterizes the extreme low water conditions of the river; therefore, this dataset is used to map what is considered a drying area. The optical and radar data can be combined to illustrate both land and drying areas on a chart (Figure 10c). For areas that have tidal variations, or intertidal zones, CHS has developed an approach where RADARSAT-2 acquisitions are synchronized with low water levels from CHS's tidal predictions [13].  
Figure 9: Segmentation result showing extracted main Mackenzie River channel and tributaries over the RADARSAT-2 Spotlight image (**a**) and over chart 6428 (**b**). Note the arrow on both maps: on map (**a**), the arrow is situated near the current centre of the main Mackenzie River channel. On map (**b**), chart 6428 indicates an area of land at the same location. The charted land area spans nearly the entire width of the current river’s location at this point. These graphics highlight significant changes in the position of the river since the creation of chart 6428. RADARSAT-2 Data and Products © MacDonald, Dettwiler and Associates Ltd. (2014/2016) – All Rights Reserved. RADARSAT is an official mark of the Canadian Space Agency.