Import DRC DIAF Roads
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|Description||Osm Import of roads data in the Democratic Republic of the Congo|
|Source||DIAF (Direction de l'Inventaire et de l'Aménagement Forestier),
through its agreement with WRI (World Resources Institute)
|Date||10 April 2017|
|Permission||CC-BY 4.0 for the original data
(initially shared under ODbL 1.0 / DbCL 1.0 / CC-BY-SA 2.0)
- 1 Goals
- 2 Schedule
- 3 Import Data
- 4 Data Preparation
- 5 Data Merge Workflow
After the successful import of forestry roads data released by the World Resources Institute in Central Africa, similar strategy has been adopted to improve the national (non forestry) road network based on 2015 DIAF data. The DIAF, who is the national institution in charge of forestry monitoring had spent significant time digitizing and putting together a road network, mainly based on Landsat imagery. This dataset was shared under open license.
The goal is to manually import all the road segments not yet present in OSM, joining them with the existing highways.
For this purpose, a detailed workflow will be followed by all users involved in this task.
- Preparation, discussion - due to start April 10th 2017 (discussion actually started already in 2016).
- Import - expected to start any time after the community has solved any issues, doubts or concerns about this import (expected April 15th 2017).
The original data is in shapefile format. The accuracy of the data varies: some segments are quite correct and can be imported with little correction, whereas some others have to be corrected manually before upload or being used as a guide to map the actual road.
Detailed on the origin and production process for the source data can be found here.
The original file has the following number of objects:
|Country||Number of nodes||Number of ways|
|Democratic Republic of the Congo||-||31,150|
ODbL Compliance verified: YES
WRI, whose website was used by DIAF to publish the data online, has given full authorization for the use of their data with the standard authorization document of the Humanitarian OpenStreetMap Team (HOT). A scan of the document can be found here. Moreover, the updated (2016) memorandum of understanding signed between DIAF and WRI mentions that all data produced through their collaboration will be released under the open license CC-BY 4.0.
As the quality of the data varies, some ways can be imported with few corrections, but others will rather be used as a guide for tracing a more accurate one, transferring the tags from the DIAF segment to the new one. Incorrect segments or segments will be ignored (deleted), whereas segments that overlap with OSM data will be conflated.
The import will be carried out by users who will read and understand the workflow wiki set for this import. For each of the X predefined areas, the process will be done with the help of a Tasking Manager project, where every mapper will download the OSM data and the WRI data into two different layers, so they can correct the WRI data and conflate it with the OSM data before they upload it to the OSM database.
Data Reduction & Simplification
The data is originally in shapefile format. You can download the original file here.
From this file, we deleted all segments that have been already mapped in OSM.
Data has been corrected of errors, duplications, overlaps, etc., but it will be checked again during the import process.
|WRI Tag||OSM Tag||Comments|
|type=*||highway=primary||3110200: Route nationale
3110300: Route provinciale
3110530: Route d'agglomération
3110710: Piste forestière
3110720: Route de plantation
|section=*||Not tagged because empty|
|type_revet=*||Not tagged because empty|
|etat_route=*||Not tagged because inaccurate and outdated||3 values, documented for only 27 road segments: Bon, Moyen, Mauvais.|
|peage=*||Not tagged because empty|
|an_ouv_p=*||Not tagged because empty|
|an_ferm_p=*||Not tagged because empty|
|sce_geo=*||source=DIAF;Africover or source=DIAF;Société Trans M or source=DIAF, depending on the value||X values: Africover, Société Trans M, DIAF, MONUC, OSFAC, PNLTHA-CTB, RGC, RRN-DIAF|
|sce_sem=*||attribution=DIAF?||Organization which compiled/ complete data: DIAF.|
|lon_sig_km=*||Not tagged because not relevant|
|lon_sig_m=*||Not tagged because not relevant|
|last_edite=*||Not tagged because not relevant||Date of reference of the last editing session (2015-06-10 for all objects)|
We will use the following changeset tags:
- comment=DIAF Roads import. DRC #project-NUMBEROFPROJECT
where imageryProvider=Bing, Mapbox or whatever imagery used while importing the data, NUMBEROFPROJECT being the Tasking Manager project number.
The initial shapefile format was opened with JOSM + Open Data plugin, and saved in osm format. After this, it was transformed into a new osm file with the proposed tags. Eventually, the file was splitted in X regions.
Data Merge Workflow
Import will be undertaken by mappers trained for this task, using an import specific OSM user account and following a [WORKFLOW LINK detailed workflow with screenshots], that shows all the steps to follow, with the goal of best keeping the consistency and correctness during all the process.
With the inputs from the list, we might open a thread in the imports list.
The full workflow wiki can be checked here.
This workflow will deal with the following issues:
1. In areas that will be with high resolution aerial imagery, users will check the accuracy of each segment against that imagery, and will correct it or trace a new one using the DIAF segment as a guide if accuracy is poor.
2. Conflating with the existing OSM highways: As explained before, the roads in the DIAF dataset that conflict with others already in OSM have been removed already. If one user finds a segment conflicting with an OSM highway, he/she will check which one is more accurate. In case the OSM way is better, s/he will combine the DIAF way tags into the existing OSM counterpart. Otherwise, the OSM way will be replaced with the DIAF, keeping the OSM way history.
3. Users involved in this import will validate the data to be imported, and correct the errors they may still have. Typical ones are duplicated nodes, not connected highways in crossroads, two close parallel segments that should be only one, very short few-metres segments that should be deleted, etc.
The workflow will follow these general steps:
1) One of the importing users chooses one of tasks of one of the Tasking Manager projects (there is one for each province).
2) S/he downloads the OSM data in one layer, and the DIAF data for that tile in a different layer.
3) S/he then opens the aerial imagery layers we have for that area. In case there are enough GPS traces, s/he can align the imagery layers.
4) S/he then corrects the errors in the DIAF data layer, like duplicated nodes, crossing ways and ways not joined to each other. Those ways that are wrong will be corrected or, in some cases, deleted and not imported. If there is any segment already present in OSM, we will conflate them as it was already explained.
5) Next, we will merge the DIAF data layer with the OSM data layer and proceed to join and combine ways to finish the task.
6) Before we consider the task finished, we will check once again for any errors and warnings in the merged layer. New errors that may appear are lack of bridges or fords in river crossings.
7) Last, we upload the data with the special OSM import account.
In case of any trouble, JOSM reverter will be used.
Conflation has already been explained in the workflow section above. It will deal mainly with joining DIAF roads to other OSM roads.