Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision Next revision Both sides next revision | ||
|
reference_book:image_virtualization [2017/07/23 22:48] admin |
reference_book:image_virtualization [2017/07/24 00:06] admin [Limitations] |
||
|---|---|---|---|
| Line 57: | Line 57: | ||
| {{ reference_book:imagevirtualization16.png?direct&600 |}} | {{ reference_book:imagevirtualization16.png?direct&600 |}} | ||
| + | |||
| + | The selected corresponding option is also presented in the status bar. Double clicking the corresponding label in the status bar brings the relevant tab from the "Options" dialog, where the "Raster map virtualization" option can be edited. | ||
| ===== Example ===== | ===== Example ===== | ||
| Line 70: | Line 72: | ||
| Some other functor such as [[:Extract Map Attributes]] and [[:Extract Categorical Map Attributes]] can produce result that is different from the result that would be obtained using the original versions of the map. Typically, this is not a problem if the information produced by these functors is used with care. For example, it is safe to extract the number of non-null cells and multiply by the cell resolution provided that the values are coming from the *same* [[:Extract Map Attributes]] or the *same* [[:Extract Categorical Map Attributes]]. This is possible because map virtualization changes the cell resolution of a map and the number of non-null cells of the map simultaneously, keeping the multiplication result consistent with the one that would be obtained by using the original version of the map. The same is true for all other attributes. | Some other functor such as [[:Extract Map Attributes]] and [[:Extract Categorical Map Attributes]] can produce result that is different from the result that would be obtained using the original versions of the map. Typically, this is not a problem if the information produced by these functors is used with care. For example, it is safe to extract the number of non-null cells and multiply by the cell resolution provided that the values are coming from the *same* [[:Extract Map Attributes]] or the *same* [[:Extract Categorical Map Attributes]]. This is possible because map virtualization changes the cell resolution of a map and the number of non-null cells of the map simultaneously, keeping the multiplication result consistent with the one that would be obtained by using the original version of the map. The same is true for all other attributes. | ||
| - | It is also worth noting that certain maps should not be mixed with other maps with different extents/resolutions such as maps representing line features specially roads. Some algorithms might assume that a road is always only one cell wide and the virtualization process might produce a map where this assumption does not hold. | + | It is also worth noting that certain maps should not be mixed with other maps with different extents/resolutions such as maps representing line features specially roads. Some algorithms might assume that a road is always only one cell wide and the virtualization process might produce a map where this assumption does not hold. |
| + | |||
| + | It is also worth noting that certain maps should not be mixed with other maps with different extents/resolutions such as maps representing line features, specially roads. Some algorithms might assume that a road is always one cell wide and the virtualization process might produce a map where this assumption does not hold. | ||
| {{ reference_book:imagevirtualization13.png?direct&600 |}} | {{ reference_book:imagevirtualization13.png?direct&600 |}} | ||