Adding reference IDs to dams in the United States - requesting guidance

I have been working on dams in the United States and need input on the next step I want to take. I’ve figured out how to do what I want to do, but I want to know if it’s okay if I proceed. Thank you for reading.


Q1: Does adding one tag with a reference ID number to 430 existing nodes and ways at once count as an import? Should I document what I’m doing on the wiki? Details follow. I tried to keep it short and failed, sorry.

Q2: Does creating a MapRoulette challenge to add reference ID numbers to 230 more existing nodes and ways sound like a good idea? I haven’t created a challenge before and wanted to ask before I just did it. Again, details follow, sorry it’s so long and thank you for reading!


So I’ve been using the U.S. Army Corp of Engineers’ National Inventory of Dams to help me edit existing dams in OpenStreetMap that according to their GNIS tags were meant to be in a different county than they actually were. Some were hundreds of miles from the correct location, some were already in the correct location and the GNIS county tag was just wrong. Some were on a border and GNIS wasn’t incorrect just imprecise.

Not all dams are big enough to be in the NID, but they have over 90,000 entries so I was able to successfully turn a lot of GNIS-imported dam nodes into ways at locations I confirmed. And when I did, after input from some helpful people on the OSM wiki, I stored the NID’s 7-character dam ID in a new tag, ref:US:NID.

Currently 1,336 dams (and weirs) in the United States have this tag. I did most of them, either while manually editing a specific dam or just while happening to go past a dam when editing in its area. Then about 130 of those were imported a couple of years ago in Iowa and southern Minnesota by someone else but I noticed they had dam IDs in one of their tags (NHD:Source_Fea) so I just copied it to ref:US:NID.

Now I want to try to match the rest of the existing dams in OSM in the U.S. to the NID. The NID doesn’t cover every dam, but it covers a lot. I decided to start with one state:

Ohio has 1425 dams in the NID. Ohio has 1037 dams and weirs in OpenStreetMap. Here is what I have, and what I want to do with it:

I have matched 430 OSM dams to the NID based on one of their name fields being an exact* match and their coordinates being within 1000 meters. The NID includes alternate and former dam names, I used those in addition to the name, old_name, and alt_name OSM tags when matching.

*Exact name match after a little bit of normalization when comparing “Number One” to “No. 1” or “Structure 7d” to “Structure No. Vii-D” for example.

QUESTION 1: Can I take these 430 existing dam nodes and ways and add one tag (ref:US:NID) to each with the NID ID number I’ve identified? Does this qualify as an import since I’m not manually editing each one? If I create a page on the OSM wiki with this information and document my progress state-by-state, is that a good idea? Or have I overshot what is reasonable to do automatically?

Then, round two. I have potentially matched 230 more OSM dams in Ohio to the NID and am ready to create MapRoulette tasks to tag them with their IDs from the NID. These were matched by proximity (OSM dam is within 750 meters of the dam in the NID) and a lack of other dams any closer. These do not match exactly by name, though many are similar. To come up with this list, I needed to use information from the Ohio Department of Natural Resources, who supply most of the information for the Ohio dams to the NID in the first place. The Ohio DNR has several thousand more dams that are smaller than those in the NID. For this I just used their data to confirm the NID entry is the physically closest thing to the dam in OSM. Sometimes the NID coordinates are right on the dam, sometimes they’re off in the middle of the body of water. I just needed to confirm another named pond with a dam didn’t sneak in between what I’m trying to match together.

QUESTION 2: Does this example MapRoulette task look ok? I realize it’s just a screenshot but I’m still messing with the task’s configuration since I haven’t done this before.

Thank you for your time and your guidance on if I should move forward or stop or what. I really appreciate it.

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