[Talk-ca] Importing buildings in Canada

[Daniel @jfd553]

Bonjour groupe!
Well, I think we are having a good discussion and are moving towards an import procedure with which everyone will be comfortable.
First, I have modified the wiki to reflect our latest discussion [1-3]. The import procedure seems to fit with current discussion. Please, have a look.
Second, about OSM vs. ODB data quality (Nate’s concern). Accuracy is a complex subject because it has multiple aspects. I examined [4] the completeness of the ODB and OSM buildings, the accuracy of the boundaries and the accuracy of the location, for all of the municipalities covered by the ODB dataset. Here is a summary of what I saw.
Data Completeness: Completeness of ODB buildings is generally much better than OSM, except when an import has already taken place (it is then similar), or for Sherbrooke and Nova Scotia (except for Halifax) areas.
Delineation accuracy: ODB buildings often have a better delineation than the OSM (e.g. right angles, level of detail) but it is far from being always the case. In some cases, which seem to depend on the census subdivision, OSM will have better building representation most of the time.
Location accuracy: Image requirements for municipal mapping are generally very high in order to properly manage their infrastructure (i.e. image resolution, ground control accuracy, DEM accuracy). Even if they use bounding boxes to represent buildings, the location of the resulting shapes is accurate. In the case of OSM, the images on which we delimit buildings footprints show very different accuracy, which leads to inconsistent location accuracy for all the features delineated over the imagery. Read above for more details [5].
Third, about who could contribute to the import? The presence of a local import manager should make it possible to assess the nature of the work done. I suggested to those who want to be a local import manager to share their intentions on Talk-ca. This means that we all know that “John Doe” will be responsible for importing “Lost City” before identifying him on the wiki page [4]. Only then should the project appear in the task manager. I also think that anyone who wishes to contribute should indicate their intentions on the list, so that their name can be added to those who are authorized to access the import tasks.
Comment, suggestions?
Daniel
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[1] https://wiki.openstreetmap.org/wiki/Canada_Building_Import#Building_Imports

[2] https://wiki.openstreetmap.org/wiki/Canada_-_The_Open_Database_of_Buildings#Import_the_Data

[3] https://wiki.openstreetmap.org/wiki/Canada_-_The_Open_Database_of_Buildings#Import_Procedure

[4] https://wiki.openstreetmap.org/wiki/Canada_-_The_Open_Database_of_Buildings#Import_Status
[5] OSM buildings (imported or not) were all delimited by images (using ortho or stereo images). The accuracy of the images depends on the derived/available elevations in the area. Municipal mapping (i.e. ODB data origin) requires high location accuracy to manage municipal infrastructure. In OSM, the available ortho-images are created using DEM, the accuracy of which differs considerably. On flat surfaces, this does not matter (the only effect is generally seen on roofs which may have an offset from building footprint location on the ground). This is completely different on hilly areas where the resulting images will show offsets that change with elevations.


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