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Welcome to the Import Guide. This page and its direct links are the main point to actively participate in this buildings import. In case of doubts you can ask for help through the talk-br list or Telegram Ceará.
Preliminary steps
These are the steps to take before you start.
- If you don't already have a user on this wiki, create an account on this wiki. Add this page to your watchlist (the star
 that appears in the top menu when you are already logged in). In that way you will receive notifications every time the guide is updated.
- The tasks are of an intermediate/advanced level, read the documentation in these pages Buildings, Simple 3D buildings and Key:building. For more help with OSM, simply consult the instructional guide.
- Create a dedicated user account to work exclusively on imports, separate from your normal account. In the description for the account profile write that it is used for the Buildings Import described in https://wiki.openstreetmap.org/wiki/Fortaleza/PMF_Buildings_Import, source: Prefeitura Municipal de Fortaleza (Fortaleza City Council).
- Install JOSM, the recommended editor for this import, if you have not already done so.
- Set up your dedicated account in Authentication Settings: Preferences (F12) > Connection settings > Authentication
- Select the Map Paint Styles Coloured Streets and [1]: Preferences (F12) > Map settings > Map Paint Styles.
- Install these plugins: Preferences (F12) > Plugins.
Buildings import
Data download
Importing data into JOSM
- When opening the JOSM, download the area you want to work, if you wish.
- Initially, the JOSM CRS must be changed: Edit - Preferences (F12) - Map Settings - Projection method - By code: Set CRS EPGS:31984.
- Add satellite layer. Suggestion: ESRI - Clarity (best resolution for Fortaleza) or Maxar Premium (most recent images).
- Import file from Tasking Manager: select desired area, click Start Mapping, and download the file clicking on the task instruction. JOSM should receive the file automatically.
- After loading the attributes, check if the image layer is aligned with the added attributes. If not, align the satellite image by right clicking on the satellite layer (right menu Layers) and selecting New offset. Adjust the image by dragging the image until it is aligned with the added attributes. Except in extreme cases, DO NOT adjust the position of the newly added attributes.
Data validation and correction
Internal validation
After loading the data into the JOSM, as in previous steps, the JOSM Validation tool should be used to check for possible errors in the imported data (verification and resolution of internal geometric and tag conflicts). Internal geometric and tag conflicts should be examined, according to the JOSM validator, in the group of original objects, in isolation, without downloading the existing one in the OSM. You must pass the validator and check the following possible geometric conflicts, in this order:
Errors
- Building duplicated nodes: select all those with conflict, and resolve with fix (it will merge). Or, add layer = 1,2,..., depending on the layer.
Warnings
- Intersection between multipolygon ways:
- Examine case by case. If both are in an outer situation (or sharing only 2 or 1 nodes), copy the tags from the multipolygon to the member ways and delete the multipolygon to which the ways belong.
- Building inside building:
- Check if they are part of the same building. If so, add building:part=yes and the correct procedure for this tag.
- Select the way and its node where the intersection occurs, split (P), delete the part that remained inside, and confirm if another (distinct) path that already existed in the same location remained.
Other conflicts, examine case-by-case. In different areas of the city the material has presented different types of conflicts. In cases where most buildings are on simple polygon ways ("non-multipolygon"), the problem of several cases of Building inside building arises, requiring individual verification of the cases.
By resolving those, many of the other conflicts are resolved as a result (such as crossing buildings).
Correction and simplification of data
Initially, the imported data must be corrected, as they are not immune to errors. We must remember that the data are from 2010, so the buildings may have been modified (geometry), or even demolished for the construction of new buildings (many cases like this in the Meireles neighborhood, for example). These corrections must be made by the importer, indispensably. In addition, there are cases where the same building has several heights (especially buildings of high heights), where the use of the tag building:part=yes should be used.
In addition, it is important to simplify the data obtained, as they come with unnecessary details to the OSM, such as several areas of the same building with equal heights, or buildings with excessively complex geometries (excess of nodes, for example).
Either way, tips for common problems (and their fixes) can be found on the Corrections tab.
External validation
After validation and correction of the imported data, one must finally verify its relationship with the existing data from the OSM, verifying and correcting conflicts.
You must first download the existing data from the OSM, and again pass the validator, now to check geometric conflicts of the buildings to be imported with existing objects in the OSM.
Warnings
- Building inside building: cases of buildings already mapped; resolution:
- between polygon and node: copy the tag building=* from the node to the polygon and remove it from the node.
- between 2 polygons:
- a. or separate and remove from this import the new building to be imported, for later verification with the existing material;
- b. or replace the previous geometry with the new one, conserving the history, using CTRL+SHIFT+G (only for ways, not multipolygons).
Solved this, pass the validator again, as other conflicts may have been resolved with this.
- Crossing buildings: Same as the previous case of Building inside building. Or, cases of nodes between neighboring buildings: merge only the perimeter nodes, leaving no lines or nodes of buildings inside other neighboring buildings.
- Crossing ways: confirm the correct alignment using satellite image and the GPS and Strava plots. It depends on the case:
- Check the need to realign the roads or other buildings involved in the conflict (given that the homogeneity of the mapping of city hall buildings was indicated as more reliable).
- Check the empty spaces between the buildings where you can realign the road without crossing them.
- Take care of any implantation error that may eventually be found in the city council material (at the top, instead of at the base); in these cases realign these new buildings to be imported.
Other conflicts, examine case-by-case. After 100% validation (internal validation, data correction, and external validation), the data is ready for upload!
Data upload
Having the data ready for shipment, some points should be noted. Initially, observing the import guidelines, a specific user must be used for the import. If this is not observed, the data can be reversed and the account can be blocked by the DWG.
In addition, add a description about the shipment, adding the hashtag #ImportPMFBuildings and as the data source the Prefeitura Municipal de Fortaleza (Fortaleza City Council). If you have used a satellite image, add it also in the source, separating it with a semicolon, such as "Prefeitura Municipal de Fortaleza; ESRI".
Finally, do not send a massive send of data at once, so as not to overload the server.
In summary, these steps must be done (in more detail again in the import guidelines):
- Check again that you are authenticated with your specific import account and not your usual OSM account.
- Make a brief description of the edition, adding the project-specific hashtag. For example: Buildings import #ImportPMFBuildings
- Add the data source, which in this case is the Prefeitura Municipal de Fortaleza (Fortaleza City Council). In case of satellite image, also add, for example, "Prefeitura Municipal de Fortaleza; ESRI".
Thank you very much for your contribution!
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