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AccessMod 5 contains a new function which aims to clean most of these artifacts (see 0Section 5.5.2). Even so, it is important to be aware of this issue and to check the result of such cleaning because the existence of these artificial “bridges” (passage in the merged land cover layer that does not exists in real life) can greatly influence the result of the accessibility analysis.

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1. A situation in which the density of artificial bridges to be corrected is low (as indicated in red in

   Caption ref
   anchor bridges

    below, road in green and river in white). In this case, the user should open the merged land cover, the road and the hydrographic network layers in a GIS software and:
   1. Generate a buffer with a radius equivalent to 1.75 time the resolution of the original land cover grid (in light blue in

      Caption ref
      anchor bridges

      b below);
   2. Put the hydrographic network layer in the editing mode and move the concerned segments outside of the buffer area as presented in

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      anchor bridges

      c below (highlighted blue line). You might also want to adjust the way the hydrographic network cuts the road network by placing them perpendicularly as also shown in

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      anchor bridges

      c below;
   3. Save your edits, import the new layer in AccessMod and run the merge land cover tool once again. The new resulting merged land cover should then look like presented in

      Caption ref
      anchor bridges

      d below.

   

   Captioneditem
   anchor bridges caption Example of correction process operated on the hydrographic network with low density of artificial bridges with rivers showing up in white and roads showing up in green (see text above for explanations)

   2. A situation in which the density of vertex on the segments to be corrected is dense (indicated in red in Figure 3a

   Caption ref
   anchor hydr_correc

   a below, road in green and river in white). In this case, open the merged land cover, the road and the hydrographic network layers in a GIS software and:
   1. Generate a buffer with a radius equivalent to 1.75 time the resolution of the original land cover grid (in blue in Figure 3b

      Caption ref
      anchor hydr_correc

      b below)
   2. Put the hydrographic network layer in the editing mode and add a new river segment outside of the buffer area as presented in Figure 3c

      Caption ref
      anchor hydr_correc

      c below (light blue line)
   3. Save your edits and run the first module of AccessMod. The new resulting merged land cover should then look like presented in Figure 3d

      Caption ref
      anchor hydr_correc

      d below

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