A 5 Landcover How to fix common topology error — Transcript

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1. 0:01Now, let's um look at this um topology
2. 0:04errors and how we can fix it.
3. 0:06So, the first one, inverted geometry,
4. 0:09which means you have created a inverted
5. 0:12polygon. So, you need to delete and draw
6. 0:15this polygon.
7. 0:18In this example,
8. 0:20like um polygon like this,
9. 0:22it's a invalid
10. 0:24geometry, okay? So, in this case, we
11. 0:27just delete it. Okay? So, we don't draw
12. 0:30like like weird shape like that.
13. 0:36And second, it's overlap. So, this
14. 0:39overlapping is not allowed. We need to
15. 0:41fix it, and I'll come and show you an
16. 0:42example.
17. 0:45So, when we draw overlap for this one,
18. 0:47right? We mark everything as overlap.
19. 0:49Sometimes, we may accidentally
20. 0:53of the land feature in another area
21. 0:56where is no overlap. So,
22. 0:59um as you can see, if we delete this
23. 1:01one, there's another layer is still
24. 1:03existing. So, it's very easy. So, we
25. 1:05just delete one of the overlapped
26. 1:08feature or uh fix this or fix it by
27. 1:11dragging the point. And let's do a
28. 1:13topology check again.
29. 1:16So, now this has gone.
30. 1:19And um
31. 1:21for the off point, so
32. 1:24for this one,
33. 1:25uh it ask you don't draw offset angles,
34. 1:29and I will give you guys an example what
35. 1:31is offset angles and uh how we can fix
36. 1:33it.
37. 1:35So, an off point looks like this.
38. 1:39Two land features
39. 1:41are pointed,
40. 1:43you know, in the offset direction.
41. 1:45So, this is not um would happen in the
42. 1:49real life scenario. So, let's take a
43. 1:51look. So, this one has been
44. 1:54misclassified as building, so we should
45. 1:56fix this uh by just change it um
46. 1:59category to driveway and then let's do
47. 2:02another topology check. Now, this has
48. 2:04gone.
49. 2:07Now, let's look at the kickbacks.
50. 2:09So, for kickbacks,
51. 2:11let's show you guys example and then how
52. 2:13we
53. 2:14identify kickback and then how we should
54. 2:17how we can remove a kickback.
55. 2:21So, here's example of the kickbacks.
56. 2:23Let's Let's take a look of what it looks
57. 2:26like.
58. 2:27So,
59. 2:28when you in the land cover project, when
60. 2:30you see a kickback, most likely there's
61. 2:33a
62. 2:34very small
63. 2:37as you can see, very small um
64. 2:40area that's a very too narrow and will
65. 2:43create with when they this two uh
66. 2:46when this two land cover features
67. 2:47connect together um and this two too
68. 2:50narrow, then um and one of them is too
69. 2:52narrow, then they will create a
70. 2:54kickbacks.
71. 2:56So, to fix this is very easy. So, we
72. 2:58select this one and also
73. 3:01we select um the narrow one beside it
74. 3:04and then we can um use V to merge them
75. 3:07together and then let's do the topology
76. 3:09check again.
77. 3:11See? It's a gone. It's gone now. So,
78. 3:15um for the up for the kickback, we can
79. 3:18fix by merging the um kickback point
80. 3:22kickback geometry into the bigger one.
81. 3:25Next is gap. So, gap means an area
82. 3:29hadn't been finished in this task. So,
83. 3:31we need to finish all.
84. 3:35Let's look at this example. Um in this
85. 3:37task, there's a geometry error mark as
86. 3:40gap. So, um there's a gap in the in the
87. 3:44middle. So, which means there's no land
88. 3:46cover category has been assigned to this
89. 3:48one. So,
90. 3:51this one um we could assign the sidewalk
91. 3:55to fill in this one. Use the fill tool,
92. 3:58and then let's do the topology check
93. 3:59again.
94. 4:01Now, the error has gone.
95. 4:05Next is a sliver edge. So, sliver edge
96. 4:08means a polygon is too narrow as a line.
97. 4:12So, we we need to use repair tool or cut
98. 4:15tool to remove it.
99. 4:18So, here's an Here's an example for the
100. 4:21snap um sliver edge.
101. 4:24Sliver edge is like um when you draw um
102. 4:27road, sidewalk, or driveway, um two end
103. 4:31is wide, and then in the middle suddenly
104. 4:33it gets too narrow, it will report this
105. 4:36topology error. So, we should be careful
106. 4:39with this um error. So, this is a um big
107. 4:43example, so here.
108. 4:45So, in in order to fix this, we should
109. 4:48um
110. 4:50fill this um road.
111. 4:56And then,
112. 4:58try again.
113. 5:00Now, the all the error has gone.
114. 5:04Next one, um is a similar one, which is
115. 5:07area too small. So, we need to delete
116. 5:10and fill in this area as a neighbor
117. 5:12class. This is um what we also encounter
118. 5:15in the building repair project, so I
119. 5:17won't show you an example.
120. 5:19The next one is a snap failure. So, snap
121. 5:21failure is a small gap between two same
122. 5:24features. So, we need to fill in the gap
123. 5:27or move the two um the or move the
124. 5:30feature uh for bigger gap.
125. 5:34So, in this example, as you can see,
126. 5:37uh this building has a small gap between
127. 5:40these two parts,
128. 5:41uh which creating a snap failure error.
129. 5:44So, in this case, we need to fill in
130. 5:48this gap to fix this error.
131. 5:52So, I will use the filling tool.
132. 5:56And then, let's do the topology check
133. 5:58again.
134. 5:59So, the error has gone.
135. 6:04So, let's look at this example of the
136. 6:07this topology error, not the most in the
137. 6:09final result. As you can see, we have a
138. 6:13a spike coming out of this pavement, and
139. 6:17also a spike in this grass.
140. 6:19So, in this case,
141. 6:21we want to repair for this
142. 6:26for this spike.
143. 6:28So,
144. 6:29it's pretty easy. We can use the repair
145. 6:32tool
146. 6:35to draw for to to fix this one, and then
147. 6:38do the topology check again.
148. 6:41Now, it's been fixed.
149. 6:45Last Last two, the first Last two, the
150. 6:48the first one is boundary error. So, I
151. 6:51I already checked have another video as
152. 6:55boundary error for connect to neighbor,
153. 6:58which means the classes is not
154. 6:59consistent at boundary. So, needs to be
155. 7:01consistent, which which means that you
156. 7:03need to be consistent at boundary. So,
157. 7:06you can check my another video. And the
158. 7:08last one, exceed the boundary.
159. 7:10Sometimes, when we draw with draw the
160. 7:14land cover features, and there's some
161. 7:16some stuff
162. 7:18parts we draw exceed the boundary, and
163. 7:21this will cause this error. So, in this
164. 7:23case, we need to use the boundary clip
165. 7:26from the toolbar to cut the polygon
166. 7:28drawn outside the boundary.
167. 7:31So, when we have a boundary like this,
168. 7:34and when we draw the forest, for
169. 7:36example, in the here,
170. 7:39we extend to the extended the boundary.
171. 7:42So, in this case, we can use this tool
172. 7:46clip the boundary
173. 7:47and then it will be gone, very
174. 7:50easy.
175. 7:51So, that's all for the topology error
176. 7:53check, and I hope everyone can
177. 7:56understand and know how to fix it in the
178. 7:59project.