...
La commande sera effectuée comme suit dans le contexte du présent exercice en considérant que les routes permettent le franchissement de barrières (ponts):
(1) Place the road layers on top of the two barrier layers, and with the landcover layer at the bottom of the stack to simulate roads passing over the rivers and wetlands (bridges), and rivers and wetlands representing natural barriers to movement in the landcover. You can order each layer by clicking on it, holding the left button of the mouse and moving it to the desired place in the list.
(2) You can use the buttons on the left-hand side to:
- Define items to be skipped during the merge after dragging and dropping them in the "Stack items to skip" part of the section. These items will not be included in the merged land cover layer. This option could for example be used to temporarily remove one particular type of roads from the stack and therefore the resulting merged land cover layer
- Skip all the items from the stack by clicking on the "Skip all items" button on the left. However, doing this would not allow creating a merged land cover layer as the stack would be empty.
- Delete the items placed in the "Stack items to skip" part of the section by clicking on the "Delete skipped items" button on the left. However, this action cannot be reversed; the layer in question will have to be added once again to the stack if needed
- Bring all the items placed in the "Stack items to skip" list back into the stack by clicking the "Use all items" button on the left
(3) The "Clean artefacts (this can take some time)" option allows users to make topological corrections after adding roads to the stack. In Figure 9 we can see that adding the layer of roads produced an artificial bridge (artefact) between cell e5 and cell d6, which appears to cross the river, while the road actually does not cross it. AccessMod can automatically remove these kinds of artificial bridges.
If you choose this option, AccessMod will output an additional raster data set that will show the locations of the cells that were identified as artificial bridges and that were removed by transforming them to barrier cells. The name of this additional data set is the name of the merged landcover, plus "bridge" (in our case here, it will be called "landcover merged bridge"). In this data set, cells that were artificial bridges have a value of 1, while all other cells have "No Data" values.
You can see this data set in the Data table (after the land cover merge process) only if you have selected "Enable advanced options in modules" in the AccessMod "Settings module" (see Section 5.9.1 below), and if you have selected “Show internal data" in the "Filter" section of the "Data" module. Please note that applying this topological correction process can significantly increase calculation time especially on big datasets, because each cell has to be processed by the algorithm.
(1) Placez les couches de route au-dessus des deux couches de barrière et avec la couche d'occupation du sol au bas de la pile pour simuler les routes passant sur les rivières et les zones humides (ponts), et les rivières et les zones humides constituant des barrières naturels aux mouvements dans les occupations du sol. Vous pouvez changer l'ordre de chaque couche en cliquant dessus, en maintenant le bouton gauche de la souris enfoncé et en la déplaçant à l'endroit souhaité dans la liste.
...
| Captioneditem | ||||||
|---|---|---|---|---|---|---|
| ||||||
(4) Give tags to the final merged land cover layer, "landcover merged" in the present exampleAttribuez des étiquettes à la couche d'occupation du sol fusionnée finale, "occupation du sol fusionnée" dans le présent exemple.
(5) Hit "Merge the items in the stack" to merge all layers that are listed in the "Stack items to use" list. A transparent window with some text and a progress bar will appear in front of the panel while the merging is occurring. Please wait until this window disappears to continue using AccessMod. Once the merging process has finished, go back to the "Data" module where you will see the new layer "landcover merged" appearing in the list, ready to be used for the different Cliquez sur "Fusionner les éléments de la pile" pour fusionner tous les couches répertoriés dans la liste "Eléments de la pile à utiliser".
Une fenêtre transparente avec du texte et une barre de progression apparaîtra devant le panneau pendant le fusionnement. Veuillez patienter jusqu'à ce que cette fenêtre disparaisse pour continuer à utiliser AccessMod. Une fois le processus de fusionnement terminé, retournez au module "Données" où vous verrez apparaître la nouvelle couche "occupation du sol fusionnée" dans la liste, prêt à être utilisée pour les différentes analyses:
To verify that this merged land cover layer is the desired one, you can visualize it by going in the "Raster Preview" tool of the Toolbox module, and by selecting this layer in the drop-down menu:
Pour vérifier que cette couche d'occupation du sol fusionnée est celle souhaitée, vous pouvez la visualiser en allant dans l'outil "Carte interactive" du module Outils et en sélectionnant cette couche dans le menu déroulant:
Note that the "Raster preview" module is not intended to be a fully-fledged GIS visualization tool, and its functionalities are limited. If you want to check more thoroughly if this layer has got the intended raster values, it is highly recommended to export it from AccessMod using the data module, import it in your GIS software and check its content before using it for the different analysis offered by AccessMod.