Elimination of Duplicate points » History » Version 1
Giulio Di Anastasio, 06/05/2021 15:09
| 1 | 1 | Giulio Di Anastasio | h1. Elimination of Duplicate points |
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| 2 | 1 | Giulio Di Anastasio | |
| 3 | 1 | Giulio Di Anastasio | h2. General criteria |
| 4 | 1 | Giulio Di Anastasio | |
| 5 | 1 | Giulio Di Anastasio | It might happen that the same physical feature (e.g. a tree, or a pole) is surveyed more than once: this can happen because there are many physical features in an area, and the survey needs more than one station. So, for example a tree is surveyed from a station, and gets a serial number on that date. When the station is then changed, it might happen that the same tree is resurveyed: another serial number is given, and possibly a different date, if the survey from the second station happened on a different day. |
| 6 | 1 | Giulio Di Anastasio | It is clear that the same tree is then represented with two different points, which means that two different trees exist: but only one tree really exist in the physical reality. |
| 7 | 1 | Giulio Di Anastasio | It is clear that one of the two points is redundant and needs to be removed. If this is noted by the surveyor directly in the field, then the issue is solved by the surveyor himself during processing time. |
| 8 | 1 | Giulio Di Anastasio | If instead, due to various reasons, it was not noted by the surveyor in the field, it will need to be cleaned after the processing, possibly by post-processing staff. |
| 9 | 1 | Giulio Di Anastasio | How to identify duplicate points? |
| 10 | 1 | Giulio Di Anastasio | The following criteria can be used: |
| 11 | 1 | Giulio Di Anastasio | 1. The distance between the two points is less than 30 cm (trees are surveyed if their trunk diameter is at least about 20 cm, so in 30 cm cannot exist two of them) |
| 12 | 1 | Giulio Di Anastasio | 2. The orig_id (serial number) of the points are not in series |
| 13 | 1 | Giulio Di Anastasio | 3. The survey date is not the same |
| 14 | 1 | Giulio Di Anastasio | 4. In case of trees, the species of trees is the same |
| 15 | 1 | Giulio Di Anastasio | 5. 5. In case of trees, the tree type is not TDEF (because TDEF are mapped irrespective of their diameter, so they can actually have a small trunk, and two of them might exist in 30 cm), not OT (many TDEF species are surveyed as OT if not otherwise indicated by a botanist) |
| 16 | 1 | Giulio Di Anastasio | 6. The context needs to be evaluated: if one tree is deleted in an area where many trees exist in a limited space, then loosing one in the map is not a big error. If instead one tree is deleted where there are very few trees, then it might be a big loss. |