I am a dedicated GPS user and map lover. I am thrilled to be able to contribute information to the Openstreetmap project and have done so already.

I have a couple of questions, one simple the other less so. How do I add a small village? I can do it in Potlatch if the town is clearly visible but I'm wondering if there's a way to locate a particular lat/lon coordinate on the editable map and then position the cursor there? I tried uploading a single point in a GPX file but evidently the OSM server is looking for a track with multiple points & timestamps and rejected my upload.

The other question has to do with auto-routing information. The area I'm living and motorcycling in right now, northern Thailand, is loaded with routing errors of all types. I'm curious to know how the various routing websites I've read about interact with OSM. Where does OSM obtain the auto-routing information included in its downloaded maps? Eventually I want to be able to correct errors I see. Where should I begin and what should I read first?

Many thanks

asked 21 Nov '12, 06:54

AlaskaDave's gravatar image

AlaskaDave
3.9k7093141
accept rate: 12%

1

For next time: better to ask each question separately on this website (and use a more relevant title!)

(24 Nov '12, 04:09) nicolas17
1

Quite right nicolas - I had the same thought myself. And I will do that.

(24 Nov '12, 04:54) AlaskaDave

I'm very ignorant on routing, but here are some places you could maybe start: http://keepright.ipax.at/ creates overlays that list errors in the map, which you can filter to list routing-related errors. http://map.project-osrm.org/ is a popular routing engine I'm pretty sure - they might have more info there. And https://wiki.openstreetmap.org/wiki/Routing might serve as a starting point for more info. Assuming you haven't seen these pages, yet.

(24 Nov '12, 19:36) dneelyep

I'll have a go at the easy question. In Potlatch 2, click the Options button, and select 'show mouse latitude/longitude'. The position of the cursor is then shown in the top right corner of the editing area. The position is shown in decimal degrees. If you have positions in some other form and are unsure about converting between the two, have a look here (https://help.openstreetmap.org/questions/10019/how-can-i-convert-this?page=1&focusedAnswerId=10022#10022).

As regards uploading single points, I have successfully uploaded GPX files containing both tracks and waypoints. For example, I might upload a file containing the track of a road and a waypoint with the road's name, or perhaps the exact location of a gate. I haven't tried uploading a file containing only waypoints, but I would expect it to work. However, I have read that OSM requires uploaded data to include timestamps. I don't know whether that applies to waypoints as well as tracks.

Routing is a subject that I would like to know more about, so I must leave that part of the question for someone else.

permanent link

answered 21 Nov '12, 08:41

Madryn's gravatar image

Madryn
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accept rate: 13%

edited 21 Nov '12, 08:43

On the "single GPX point" question, you can upload GPX traces with waypoints in them, and they can be very short GPX traces with only one waypoint in them. If you have a look at this example you can see one that I uploaded earlier that's almost the minimum number of track points that the OSM server will accept. Once uploaded GPS waypoints will appear as orange dots in Potlatch 2 - "alt-click" on them to convert them to nodes and then edit the tags accordingly.

(21 Nov '12, 08:56) SomeoneElse ♦

Thanks for the reply Madryn. I know about the lat/lon option and it helps but trying to position the cursor so it matches the coordinates of my point exactly is difficult to say the least. Try to position the cursor exactly at N17.79284 and E100.37506. Then, once you've done that, try to remember exactly where that point was on the screen because you'll need to position the little city icon directly over that point. There must be a better way. This portion of the OSM worldmap has no Bing imagery, it's a complete blank except for the existing ways, so this task is made just that much harder.

(21 Nov '12, 08:59) AlaskaDave
2

Potlatch 2 does not have an option for inputting direct lat/lon co-ordinates and will not do so. If you want to do that you'd be better off using JOSM.

But I'm curious as to why you want to position a village with that degree of precision. Is it a really tiny, molecular village?

(21 Nov '12, 09:14) Richard ♦

Yes, I'm wondering why you need a GPS to locate a village in OSM. Is this village not visible in Bing imagery ? Is it the Smurfs village ?

(21 Nov '12, 10:00) Pieren

Thanks. I see the difference between my file GPX file and your track file. The server rejected my file because it contained no track points, only a waypoint. These are obviously two different beasts and use a different format in the XML code. My file has this: (only the essentials are shown and GT and LT symbols replaced with brackets):

[wpt lat="17.792843962088227" lon="100.37506400607526"]

while yours contains these:

[trkpt lat="53.3291042" lon="-1.8407796"[/trkpt]

[trkpt lat="53.3291164" lon="-1.8407467"[/trkpt]

[trkpt lat="53.3291203" lon="-1.8407198"[/trkpt]

The only question I have is why the OSM server is so fussy. It seems that small towns, or other single point entities (oilwells, springs, etc.), would want to be added all the time. Why not make it easier?

Thanks very much for your help...

(21 Nov '12, 10:35) AlaskaDave
1

@Pieren and Richard - there is no Bing imagery in the area. And no it is not a microscopic village nor a Smurf village but I'd rather be as accurate as possible whenever I can. Plus, I did have the exact coordinates so I reasoned, why not use them? That raised the issue of how one would go about putting a single point on the map. My example of oil wells is something I might be interested in adding to my Alaska contributions someday.

(21 Nov '12, 10:41) AlaskaDave
1

I'm guessing here, but perhaps it's to try and encourage people to upload full GPS traces (i.e. doing a survey) rather than just waypoints (which someone could just copy from some other source)?

If you want to just position something at a certain lat / long you can do this with JOSM, of course.

(21 Nov '12, 10:42) SomeoneElse ♦

@AlaskaDave: understood; I'm just not convinced that a village can have co-ordinates that are quite that precise. The village where I live is about one mile from east to west, and half a mile from north to south: there's no need for five decimal point precision there. Even a very very small village would struggle to need that degree of accuracy.

(21 Nov '12, 12:26) Richard ♦
2

It's not especially difficuly in Potlatch 2. Place the node at roughly the right place on the map, select the 'show mouse latitude/longitude' option, and then drag the node until it is at exactly the required position. Zoom in if necessary to increase the resolution. It is worth noting that, when using decimal degrees, five places of decimals define a position to within a little less than ±50cm. There are hand-held GPS devices that can achieve that kind of accuracy, but they are intended for professional use, and they aren't cheap.

(21 Nov '12, 12:53) Madryn

I thought the fact that time stamped GPX traces are less likely to be illegally copied from a copyrighted maps, although not impossible, is the reason the system is rightfully fussy. As Madryn says if you zoom in, while in edit mode even in P2 it's not hard to fix a lat lon. I would think that walking around the block with you gps will give a useful trace and better accuracy.

(21 Nov '12, 13:45) andy mackey

Ah, the zooming tip is a good one. No need to position a town that accurately anyway as any town is much bigger than one point. But should I decide to locate those oil wells I mentioned earlier, this tip will help.

In the meantime, I'll start looking at using JOSM.

Thanks to all. Question one is answered.

Still looking for an explanation of how the various routing platforms work together though.

(21 Nov '12, 14:00) AlaskaDave

If you follow the links from the wiki there's quite a bit of info on that. Bascically, each platform infers what it can from what's added to the data - as long as you add "what is correct" to the data, all should be OK. Don't worry about "tagging for the router".

(21 Nov '12, 14:51) SomeoneElse ♦
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question asked: 21 Nov '12, 06:54

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last updated: 24 Nov '12, 19:36

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