Why am I against wholesale import of administrative boundaries from any 3rd party source for the PhilippinesPosted by maning on 11 August 2015 in English (English)
Disclaimer: This is specific to the Philippines, not a general OSM issue.
One of the most difficult data to collect in OSM are administrative boundaries (
admin_level=*). It defies the on-the-ground rule. One cannot just go out and start surveying admin boundaries with a GPS. On the other hand, we see the importance of having admin boundaries in our database. We can define town/city limits. It improves geocoding. The maps looks nice. Humanitarians need them because they can plan and allocate resources according to administrative jurisdictions during a crisis. The only logical way to have this in OSM is to get them from various sources and do an import.
The most comprehensive source we found for the Philippines is from the freely available GADM. This website has a comprehensive collection administrative boundary data for free down to the smallest administrative units for many countries including the Philippines. Over the years, I tried to track down the provenance of GADM’s PH data. My geo-forensic skills lead me to people saying that the PH dataset originated from our national mapping agency. So, it seems very authoritative, why don’t we just import them? I say NO and here’s why (again, I am pertaining here to the Ph situation, GADM data maybe good in other countries and I have the utmost respect to the maintainers of the site sharing this to the public).
Even if the license is compatible, the data quality is REALLY bad. Again, from Eugene’s mail to the list, here’s screenshot comparing OSM and GADM boundaries in Quezon City.
If the above arguments does not dissuade you, consider this story.
Administrative boundaries imply a level of authoritativeness in the data. Ordinary users of the data may take it as exact and definitive. For example, during the immediate relief operations after Typhoon Haiyan in the Philippines, OSM volunteers across the world participated in the remote mapping response. We generated a tremendous amount of building, roads, and landuse data which were used by many international response agencies. Since we lack and can’t remotely map admin boundaries in the affected areas, response agencies resorted to using 3rd party admin boundaries (GADM is one of them) as an overlay to OSM derived basemaps. These maps were used by humanitarian agencies to organize relief operations. When I went to the affected areas months after the Typhoon, local authorities are complaining that in some instances, international agencies are insisting in their own maps particularly the village boundaries as a basis of relief supplies allocation. Local authorities would insist that these boundaries are wrong and does not exist in reality. Of course, response and relief planning should be dependent on other factors and not just based on a map, but, a wrong map exacerbates an already confusing situation.
So am I saying that we shouldn’t be adding admin boundaries in the Philippines? No, what I’m saying is that any 3rd party admin boundaries that covers the whole country you stumble upon either from the internet or directly from various agencies are wrong. No comprehensive data exist in the Ph.
What can we do now?
Talk to your local government authorities. You may find good data from specific local government units, if ever you get a hold of such data, let us know and if it is good enough, we can start the process of adding them in OSM.
Go out and survey! Map places as nodes. Oftentimes, a place node (
place=town,city,village) is enough. For finding places in OSM, would you want a geocoder to give you a wrong boundary/polygon or a node/point that tells you exactly that this place exist in reality? In many cases, this is what I’m trying to do. Here’s a screenshot of village nodes we mapped in a remote town in Leyte. Compare that to the inaccurate (by 3 kms south) imported boundary of the town. Unless we get a better source to replace this boundary, I would rely more on the place node we surveyed with the local community.
I know, sometimes, it is very frustrating, OSM is heralded as one of the best freely available geographic data, yet, we lack the most basic admin boundaries over many areas. Imports might be the immediate solution, but, I ask PH mappers no to do this. I’m fine with missing boundary data for now, in time we can improve this the OSM-community-way, by importing, we maybe propagating more errors rather than helping improve our map.