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#1 2008-05-31 22:53:12

dunmappin
Member
From: Binfield Heath, Oxfordshire
Registered: 2008-05-26
Posts: 4

Raw GPS data in JOSM

I am steadily learning the art of data creation in JOSM, and enjoying it for the most part.
I understand that I should not convert to the Data Layer or upload to OSM a .gpx file that I have opened.
However, I feel there are occasions when there would be less work than adding new nodes and segments if I could simply remove certain nodes that are incorrect or surplus to requirements in the .gpx layer and create ways from those remaining.  Is this possible?
On a similar subject, when adding nodes over an opened .gpx layer, is there a method by which a newly added node can be 'snapped' to a point in the .gpx layer?  I imagine not, but I find the crosshair too crude to carry out this task with any accuracy - zoom in and the two points are some distance apart, yet one cannot realistically execute work zoomed in to such an extent.  Similarly with the 'tool' (I can't think of its proper term) of a diamond with four squares in it, or four NSEW arrows, that is activated by the 'Select, move and rotate objects' button.
What tips do experienced users have?

As so often happens, I post a query, only to find an answer, following my own further investigation.
In this case, I found the answer to my first question, at least, in http://josm.openstreetmap.de/wiki/RicksHowToPage, for which, I thank him.
I believe, although I cannot replicate it at the moment, that a warning of some sort appeared when I first clicked 'Convert to data layer' that dissuaded me from carrying out the action.  With the comfort of someone else's advice, I proceeded through that action to a satisfactory conclusion.

One further question, on the subject of coordinates, is there any method by which they can be altered for a node by typing?

Last edited by dunmappin (2008-06-01 08:55:55)

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#2 2008-06-01 13:53:52

the_winch
Member
Registered: 2008-02-24
Posts: 21

Re: Raw GPS data in JOSM

dunmappin wrote:

On a similar subject, when adding nodes over an opened .gpx layer, is there a method by which a newly added node can be 'snapped' to a point in the .gpx layer?  I imagine not, but I find the crosshair too crude to carry out this task with any accuracy - zoom in and the two points are some distance apart, yet one cannot realistically execute work zoomed in to such an extent.

Gps devices are not very accurate. Clicking at a zoom level that is reasonably easy to work with should get you well with in the accuracy range of the gps device.

As an example here is an image from an area with lots of gpx tracks overlaid on the map.

screenshotpw5.png

Since it's a map the roads are drawn much wider than reality so they are easy to see. Even so there are still plenty of gpx points outside the bounds of the roads.

The ratio of gpx points I record to the number of nodes I make is probably 50:1 if not higher. That's a lot of nodes to delete.

Last edited by the_winch (2008-06-01 13:55:22)

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#3 2008-06-11 11:55:50

daveemtb
Member
Registered: 2007-11-27
Posts: 24

Re: Raw GPS data in JOSM

I can't quite understand why anyone would want to convert GPS data to nodes and ways. The ratio of points to nodes for me is about 15. If you record GPS points at an interval that will give you an accurate indication of the shape of ways, you will have far too many points to convert to nodes.

Also, i've seen some appalling quality data produced by direct conversion, where innsuficient decimal places in the GPS data has lead to stepped ways, that are a poor representation of topology, make the DB les efficient,  and look awful on maps.

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