Changes between Version 2 and Version 3 of UsersWikiSimplifyPreserveTopology
- Timestamp:
- 04/08/12 06:33:00 (15 months ago)
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UsersWikiSimplifyPreserveTopology
v2 v3 3 3 == What we want == 4 4 5 Simplifying this layer: 6 7 [[Image(SPT_dept_ori.png)]] 8 9 into this: 10 11 [[Image(SPT_dept_sim.png)]] 5 || Simplifying this layer: || into this: || 6 || [[Image(SPT_dept_ori.png)]] || [[Image(SPT_dept_sim.png)]] || 12 7 13 8 == The data == … … 25 20 == Principle of simplification == 26 21 27 Based on the technique described here [[]], we extract linestrings out of polygons, then union and simplify them. 28 st_polygonize() is used to rebuild surfaces from linestrings. Attributes from the initial layer are associated with simplified polygons. 22 Based on the technique described here [[]]: 23 * we extract linestrings out of polygons, 24 * then union and simplify them 25 * st_polygonize() is used to rebuild surfaces from linestrings. 26 * Finally, attributes from the initial layer are associated with simplified polygons. 29 27 30 28 == Steps == … … 98 96 [[Image(SPT_bad_attributes.png)]] 99 97 100 8. Second method is based on percentage of overlaping area comparison. It gives better results in our testcase.98 8. Second method is based on percentage of overlaping area comparison. 101 99 {{{ 102 100 create table simpledep as ( … … 107 105 ); 108 106 }}} 107 108 It gives better results in our testcase: 109 110 [[Image(SPT_good_attributes.png)]] 111 109 112 110 113 9. rebuild departements by grouping them by code_dept (other attributes could be re-associated here):
