Trees in OSM - Manchester, UK

Hi, I have several questions as a new user of OSM.

What I’m trying to achieve:
I am trying to produce detailed representations of street-trees (ie, trees on the public street, as distinct from nearby trees on private land). We have a group locally that wants to encourage interest and understanding about street-trees. We are trying to persuade the local city council to alter their management plan for street-trees. It appears to be too happy to remove mature trees before the end of their safe life. There is plenty of discussion about the plan. But information about the actual trees over the whole area is not so good.

What I’ve done so far:
I don’t have a GPS, but I have a bicycle, which is pretty good for making ‘traces’ along a known way. I count the pedal turns and record the tree details using a voice recorder on my mobile phone. At home, I have transcribed the recording in a spreadsheet. I have then converted the ‘pedal-count-units’ into decimal fractions of the street length. Using the known lat and lon values for the nodes at the ends of the street, I have been able to calculate the position of each tree along the street. I’ve recorded details for several streets but have only made up OSM layers for one street. I have been able to put the result up on a web page. The hosting space has been loaned to me by a local residents’ group, here.

What I would like help with:

First - can I overcome the problem of having the tree markers ‘move’ when I zoom to a new level? The map I made (link above) is set at zoom 17. If I zoom in, the trees appear to shift. Is that just because of my lat lon values needing more accuracy? It seems unlikely. There is a related problem identified here but I’m struggling with finding a full discussion of this that I can understand.

Second - can I overcome the first problem by removing the icons at a particular zoom level? I’d like to remove them when someone zooms out anyway. Perhaps I can make them only visible at the level where they work ok.

Third - if I overcome the first problem, can I make the icons change size according to the zoom level?

Fourth - I have included a ‘mouseposition’ line in the code for the page, but it produces figures that are not lat lon values. What am I doing wrong? And how can I put it right?

Fifth - I’d be very happy to place the tree locations as nodes on the OSM server. But I don’t want to do that if it is not good for the project as a whole. There are issues with the level of detail I want to make available, and how often it will change over the 20 years of the council’s felling and re-planting plan. Can anyone suggest my best course of action on this?

Other points:
I’ve really enjoyed trying to get to grips with OSM and the JOSM and OpenLayers. I’m very new to it. But there’s very little help that can be easily found to address the problem I found in the fifth point above. For someone who doesn’t want to commercially exploit the OSM data, but isn’t sure about adding their features of interest to the server, there isn’t a clear point of information about how to create your own page and credit OSM. If I’ve missed the place, I apologise. I have been looking in a lot of places. Of course, if I feel I’m in a position to write such a page, I’ll happily add it to the wiki. But I’m far from confident enough at present.

Oh, and one last point. When I saw the Bamberg (Bavaria) street trees, I tried to find out who might have edited them. I downloaded a bbox to JOSM and found the node id for a tree. Back on the OSM page, I looked at the history and searched the id numbers. But I eventually became convinced that the id numbers on the history page are edit id numbers and that’s completely different from a node/feature id on the map. Is there any way to check out the history of a feature using its id…?

Thanks for reading all of that, and happy holidays if you’re reading it in the next few days.


To answer some of your questions:
1st: I think this is due to the icon sizes, and the offset. I think the position on the map is based on one corner of the icon (the bottom right corner?), not its centre. So when you zoom in, that corner stays in the same place, but the icon appears to move relative to the map.
As your icons are 24*24, you should set the iconOffset column for all of them to -12,-12. Then the position will be relative to the centre of the icons, and they should appear in the same place when you zoom in or out.

2nd/3rd/4th questions: that’s probably possible, but I don’t know enough Javascript or Openlayers to say how to do it.

5th: I think its fine to add all of the trees to OSM, so long as they exist on the ground. There are tags for extra details, eg height or species. There have been a few imports from official sources that added all of the trees in a city, I think they are fine.
For trees that don’t exist on the ground (eg the gaps or felled trees on your map, or planned/proposed trees), I don’t think they should be added to OSM. Though others may disagree with this.

For crediting OSM, see the Legal FAQ:

For your last point: Every node/way/relation has a unique object ID. You also have changesets, which are a group of edits made by one user, at about the same time. If you look at the history tab, it lists changesets with their IDs.
You can select an object in JOSM, then press Ctrl+H to view its History in your browser. eg something like this page:
You can change the number to look at a node with a different ID if you want.

Thanks Vclaw. That’s fantastic. With your quick response, I’ve fixed the apparently wandering icons and everything looks real good.

On adding to OSM, I figured there’d be a mismatch in what detail would suit the different needs of the OSM project and the trees group. I guess once I’m clear how it’s going to be, I can start looking at uploading the existing trees to the server. I’ll need to find a way of doing them in batches tho’. There are about 1000 trees just in this area and with a list of attributes each, that quickly becomes a big job. Good to get your answer to confirm my thoughts, so thanks again.

The legal credit that appears on the page I made is “Data CC-By-SA by OpenStreetMap” with the link for OSM. I didn’t actually put it there, it comes with the basic map. I’m not sure how to add the word ‘contributors’. Anyone got a tip on that?

Still a big thorn in the side of my head:
…is the mouseposition problem. Anyone else able to help here? Every time I see this employed in other example pages, it uses the same code as mine.

    map.addControl( new OpenLayers.Control.MousePosition() );

But on my page, the values are not deg of lon lat (although they are related to the lon lat values in that they pass through zero at Greenwich etc.

For node history, what you explained, Vclaw, was really handy. Another thing worth saying for any other new user (I’ve found just now) is the Data check box in the layer switcher (plus sign at top right). This brings up the data for the bbox you’re viewing and lets you select features and see their id as well as examine their history. It was the two different id sets that threw me. That and not being able to find the id set I wanted. Again, many thanks Vclaw.