Updating County Park's Boundaries (California - Santa Clara County)

I am relatively new to OSM so it might be that I just don’t know how these updates are done. There is a new County Park but the boundary displayed in OSM is partially incorrect. When I attempted to update it using JOSM, I discovered I could! From the little I could see from JOSM, it appears the boundary is stored separately. What is the procedure in correcting this mapping data? It would be nice if the data could be downloaded from the county GIS system rather than having to be “transcribed”. However it is done, I will do the dirty work if someone can tell me how to do it. Thank you, Harrison

Inter linking datasets would be a nice feature. There are some technical issues that need to be overcome before we could even consider doing it. For example, persistence of the id. Not all city/county/state/federal data has a persistent id. OSM doesn’t have any either. The closest is the wikidata tag to reference a Wikipedia article. For now we are stuck with adding the data.

Edit relation is best done in JOSM as you discovered. Learnosm.org has some instructions on how to edit relations at https://learnosm.org/en/josm/josm-relations/. If the boundary doesn’t use other boundaries in the relation, then editing them is straight forward. However, if the boundary shares segments with other boundaries, such as the city boundary, then it gets more complicated.

Once complete, feel free to ask for a review. Checking the request review when you upload your edit is one way. A better method is to join Slack at https://slack.openstreetmap.us/.


Clifford, thank you for the information. I will try to adsorb all of the information as quickly as possible. I have good news and bad news: The bad news is I drop “NOT” at the end of the sentence, “When I attempted to update it using JOSM, I discovered I could!” Actually, I could move the middle of the segments denoted by a “+” but not the ends so I don’t think this constitutes “editing”. And, I have no idea what would have happened if I had saved it.

I would still like to know how to “edit” such boundaries and may have the need sooner rather than later because I discovered that this problem was introduced into OSM by a “mapper” who downloaded “incorrect information” from the Santa Clara County Park’s website on the Park boundaries and used it to update OSM. I really want to know how to do that too! But, before I can, I have to report the problem to the County Parks Department and await their fix. I’m hoping the ones supporting GIS are working from home during the “lockdown” because the Park Rangers I encounter on my hikes probably wouldn’t be able to help resolve this issue. Thank you again, Harrison

If this is not the appropriate forum, I will repost this in the correct forum. From my prior posts, I want to “edit” a relation using JOSM, but canNOT. The relation is a “boundary” and contains a “road” that I would like to remove to learn how to “edit” such objects. The specific “boundary” I would like to change is the “Coyote Lake Harvey Bear Ranch County Park”, way 28520244 between Morgan Hill and Gilroy in Santa Clara County, California. The last changeset that apparently added the “road” was 79721602. In JOSM, I can “click” on the relation and both the “boundary” and the “road” I would like to remove are highlighted on the map. I am sure it is simple, but how would I “select” this object so I can remove the “road” from the “boundary”? For learning purposes, I want to perform this edit myself so could someone please just explain how I would select this object so I can “edit” it using JOSM.

I’m not seeing a boundary relation for the park. The park is just a polygon that doesn’t appear to be connected to any other feature. I see that in changeset https://osmcha.org/changesets/79719609/ a boundary was added around the road leading into the park. From conversations with the Washington State Parks Department, they only exclude the area around the roads because another department is responsible for its maintenance. They have no problem if we just make it part of the park. I can’t say how California would answer the same question. (We have some with the road buffer and some without in WA)

If you just want to remove the road buffer, just select the nodes on either side of the road, split the way, delete the buffer section, then connect the two nodes to complete the polygon. You may get some push back from user doug_sfba so I’d send them a message first.

If I misinterpreted you message, please let me know the relationship id.

As for the appropriate forum. Nothing wrong with this one, it’s just that we have more users on Slack and not many on this forum. We actually have a channel on Slack to watch for message on this forum. That’s where I saw your message.

Clifford, thank you for the assistance. I have done a lot of OSM “editing” and never encountered the difficulties that I did on this one. The “boundary” around the road has now been deleted. I have never seen this before in any California parks but it might be logical if the road maintenance was performed by a different department/division than the parks department. I have also emailed the Parks Department asking them to clarify why the information from their GIS system differs from the official document ion on the expansion of the park and, if necessary, will update OSM. I added OSMUS to my virtually unused Slack account and will endeavor to use it in the future if I again need help. Since I could not get Google Maps to “correct” their errors and omissions, I have become a substantial contributor to OSM but only for southern Silicon Valley area where I live. Even so, the information missing or in error is overwhelming!

I’m like you, I tend to focus on areas I know. I did update/add all of the state parks in Washington State. I’m also focused on getting reservations mapped in OSM, which gives me time to edit boundaries. They can be a real pain when the relation share other features.