OpenStreetMap User's Diaries
Mapping buildings in Africa or other remote locations
Sometimes I think I’m a bottom feeder going through the map and cleaning up the obvious errors and this comes from my observations over time and cleaning up thousands of duplicate buildings.
Because many countries do not have good census data you can do a rough calculation by multiplying the number of houses by an average number of people who live in them. It isn’t perfect but if you ha
Sometimes I think I’m a bottom feeder going through the map and cleaning up the obvious errors and this comes from my observations over time and cleaning up thousands of duplicate buildings.
Because many countries do not have good census data you can do a rough calculation by multiplying the number of houses by an average number of people who live in them. It isn’t perfect but if you have nothing better then it works.
So duplicate buildings are a problem. When you’re looking to see how many schools you need duplicate buildings mess the numbers up. Buildings incorrectly tagged or not tagged at all also mess the numbers up.
Then we get to the imagery used. These days I’m seeing more and more microsoft BuildingFootprints tags on buildings. They are normally very accurate and align well with Bing imagery. The largest most accurate satellites are only accurate to 60 meters so the imagery has to be aligned. My recommendation would be to use Bing imagery and find a building that aligns with it. Then switch to your preferred imagery and align it with the Bing aligned one.
This helps ensure that buildings are only mapped once and when you add buildings you don’t add an existing building and if someone imports using microsoft BuildingFootprints then your building won’t be remapped 10 meters away in the future.
Disposable mappers are often used meaning many will only may a few times. So we don’t really have time to train them.
We want to get the most accurate mapping we can from them and as many buildings as we can. With JOSM buildings_tool plugin I can highlight one building then add more by clicking and holding down the button, moving to the opposite corner of the building and releasing the mouse button. If they aren’t in line it takes another mouse button click. You get a rectangular building correctly labelled. This is far less than using iD. Plus you don’t need a validator to inspect each one to see if it is correct.
You need to install JOSM and Microsoft openJDK but you’ll get a lot more buildings out of them. It is possible to set it all up on a USB stick and run it from there.
With iD mapped buildings there is room for error in tagging. Some aren’t tagged at all, I’ve seen some tagged barrier=fence amongst others. Also many buildings are rectangular in shape but you won’t think it from the mapping.
The buildings tagged microsoft BuildingFootprints implies an import. Officially there is a formal process for an import. If you are importing please follow it. Part of the requirement is to visually check to see if the building has already been mapped. I strongly suspect this is not being followed in all cases.
Thanks for reading
John
Sometimes I think I’m a bottom feeder going through the map and cleaning up the obvious errors and this comes from my observations over time and cleaning up thousands of duplicate buildings.
Because many countries do not have good census data you can do a rough calculation by multiplying the number of houses by an average number of people who live in them. It isn’t perfect but if you ha
Sometimes I think I’m a bottom feeder going through the map and cleaning up the obvious errors and this comes from my observations over time and cleaning up thousands of duplicate buildings.
Because many countries do not have good census data you can do a rough calculation by multiplying the number of houses by an average number of people who live in them. It isn’t perfect but if you have nothing better then it works.
So duplicate buildings are a problem. When you’re looking to see how many schools you need duplicate buildings mess the numbers up. Buildings incorrectly tagged or not tagged at all also mess the numbers up.
Then we get to the imagery used. These days I’m seeing more and more microsoft BuildingFootprints tags on buildings. They are normally very accurate and align well with Bing imagery. The largest most accurate satellites are only accurate to 60 meters so the imagery has to be aligned. My recommendation would be to use Bing imagery and find a building that aligns with it. Then switch to your preferred imagery and align it with the Bing aligned one.
This helps ensure that buildings are only mapped once and when you add buildings you don’t add an existing building and if someone imports using microsoft BuildingFootprints then your building won’t be remapped 10 meters away in the future.
Disposable mappers are often used meaning many will only may a few times. So we don’t really have time to train them.
We want to get the most accurate mapping we can from them and as many buildings as we can. With JOSM buildings_tool plugin I can highlight one building then add more by clicking and holding down the button, moving to the opposite corner of the building and releasing the mouse button. If they aren’t in line it takes another mouse button click. You get a rectangular building correctly labelled. This is far less than using iD. Plus you don’t need a validator to inspect each one to see if it is correct.
You need to install JOSM and Microsoft openJDK but you’ll get a lot more buildings out of them. It is possible to set it all up on a USB stick and run it from there.
With iD mapped buildings there is room for error in tagging. Some aren’t tagged at all, I’ve seen some tagged barrier=fence amongst others. Also many buildings are rectangular in shape but you won’t think it from the mapping.
The buildings tagged microsoft BuildingFootprints implies an import. Officially there is a formal process for an import. If you are importing please follow it. Part of the requirement is to visually check to see if the building has already been mapped. I strongly suspect this is not being followed in all cases.
Thanks for reading
John