OpenStreetMap 開放街圖
So, today my friend, an urban planner, asked whether she can download a group of land-use data in her city for research purposes. Realizing that this kind of tag in OSM particularly in Indonesia still an excommunicated object mapped, so I just wanna remind that this data is very helpful and powerful for the urban planners. She also asked me if there is a highway data that has a polygon base data not only a line so her data measurement become more accurate.
This is a good idea, have you ever map a polygon highway ???
討論
由 Sanderd17 於 2020年06月11日 07時16分 發表的評論
Landuse being excommunicated? I guess it’s just the last type of data that gets mapped, because it’s hard to map. The borders are often not that clear, and you need to combine local knowledge with aerial images to get it correct.
Usually, streets as ways are added first. It’s easy to trace those with a GPS, and to see those on aerial images. After that, points of interest (shops, pubs, …) are usually added, since (as the name describes) they are interesting to many people.
Only after those features are rather complete, the community usually starts with mapping area-type objects. First the big and important areas (important buildings, big landuse around cities, river and lake outlines, …), until more and more smaller areas follow.
Highways are of the smallest area types. There have been proposals to map highways (like osm.wiki/Proposed_features/area:highway), and you are allowed to map highway areas. But it’s usually the very last thing that gets mapped, and it needs a very active community to keep that maintained.
So while every mapper can decide for himself what his priorities are, the above is the usual order things happen in.
由 Akrimullah 於 2020年06月11日 13時21分 發表的評論
Hi Sanderd17,
I can’t say more. you give me a very comprehensive insight. Maybe I need to find more literature about landuse in the OSM paper journal.
Thanksss
由 Dick Tecktiv 於 2020年06月11日 20時42分 發表的評論
Hi !
Usually, even if highways are not polygonization, neighbouring areas are.
I haven’t logged in in like 10 years so I’m definitely not in the project.
But did she consider measuring the width of unused land around highways, that are close to the real highway size ?
由 Akrimullah 於 2020年06月11日 23時30分 發表的評論
Hi Tecktiv,
Neighbouring areas both around the highway and the building are counted as area tag in OSM that could be land use, amenity or the other area type. this kind of area tag mostly as Sanderd17 said usually are the object that mapped after the easiest object already added. In my country, Indonesia, it’s rare to see those group of area objects. However, tag like amenity is common in the big city, while area tag like land use isn’t. Maybe in the future, there will be more mapper added this object frequently that collaborate their local knowledge and updated imagery in OSM.
OSM is really powerful… the data is beyond of local government has in some developing country.
由 kucai 於 2020年06月12日 04時12分 發表的評論
Shouldn’t she be asking the authorities for this data instead? Getting data from OSM contributors have so many accuracy issues, whether the classification or the correct boundaries.
Even the small town that I lived in has a fully GIS mapped information in store at the municipal’s office which is located in district’s capital almost an hour away. I was quite surprised with that discovery since the road names in my town are not even complete, yet there’s this complete map and land ownership info available at their finger tips (local district). Local governance yo..
Anyways, a side story there. Ask her to inquire with the city, her job could probably be many times easier.
由 Akrimullah 於 2020年06月12日 05時55分 發表的評論
Hi Tuan Kucai, apa kabar ??
Some country has a different level of data availability. Somehow the government staff keeps their data as confidential information. My friend actually acknowledges the building data in her town is the way more updates than the local govs has. Besides, it really hard and take a very long time to acquire data from local govs here. Even at the city level, I experienced it before. It’s very funny if she goes to ask for local govs data because her job could take a long time to be done or even if she waits for it, the data could probably not better than OSM has. So far, the alternatives either from the opensource platform or ask someone who works in the private sector. btw thanks for sharing your story. knowledge comes from reality.
由 Sanderd17 於 2020年06月12日 06時24分 發表的評論
Not all governments want to share that data (or it can be very expensive).
In Belgium, the government had top-class imagery (25cm pixels, inaccuracy of max 10cm, taken every year in the spring), and top-class GIS data (buildings with an accuracy under 1cm on the streetside, road areas, …) .
It was all done with tax money, yet it took a few years of lobbying to get access to it.