[talk-au] Way errors in Quilpie Qld

[osm.talk-au at thorsten.engler.id.au]

The correct offset for imagery can change very quickly from one place to another (alignment could be right at one place and off 100m down the road if the imagery is distorted).

 

JOSM has an “imagery offset database” if you install the right plugin:

 

https://learnosm.org/en/josm/correcting-imagery-offset/

 

you can use that to upload your corrected offset for a specific place and imagery layer so that others can get that offset from the db.

 

But this requires that people are conscious of the need to check the imagery offset before they do any work, and I think it’s only used by JOSM, not iD and other editors.

 

From: Graeme Fitzpatrick <graemefitz1 at gmail.com> 
Sent: Sunday, 3 October 2021 12:20
To: Andrew Davidson <theswavu at gmail.com>
Cc: osm.talk-au at thorsten.engler.id.au; OSM Australian Talk List <talk-au at openstreetmap.org>
Subject: Re: [talk-au] Way errors in Quilpie Qld

 

Is there any way for all of the various sets of imagery to be automatically corrected to each other to get around this problem?

 

Thanks

 

Graeme

 

 

On Sun, 3 Oct 2021 at 12:02, Andrew Davidson <theswavu at gmail.com <mailto:theswavu at gmail.com> > wrote:

On Sat, Oct 2, 2021 at 10:46 PM Thorsten Engler via Talk-au
<talk-au at openstreetmap.org <mailto:talk-au at openstreetmap.org> > wrote:
> I would assume that the lot boundaries recorded in DCDB are "exact" and any
> discrepancy between them and the physical world come down to the margin of
> errors the surveyors did when placing boundary pegs at some point.

I tried to check against any survey marks that you might be able to
locate on the imagery. Unfortunately there are no survey marks in
Quilpie from the GNSS era of surveying. I did manage to find one near
town that you can just make out where it would be on Bing:

https://qspatial.information.qld.gov.au/SurveyReport/SCR183342.pdf

> Bing is almost right: -0.15; 1.79

I get -0.10;1.50 which, considering that we are looking at aerial
imagery with a pixel size of ~0.15m, is the same thing. This is all
based on GDA94, so in theory all of the GPX traces will be offset by
about 1.63 m

I have done a best-fit and moved the town about 11 m to the west.
There are some things (e.g. the rail line near the sale yards) that
need to be better traced. I will have a look at these later.

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