[OSM-talk] [OSM-newbies] Tracing and offset error

[Gerhardus Geldenhuis]

Thanks for the reply Michael,
My concern was not so much about the imagery being out of date, as I only
trace places that I am very familiar with albeit having visited a long time
ago. I will be visiting a few places I have mapped soon and will be having
my GPS switched on all the time. It generally has good accuracy +- 3m, so
should be a good start to help correct any potential offset errors if any.

Regards


On 8 December 2012 10:16, Michael S <michael at elfu.de> wrote:

>  Since I am also interested in this discussion I'd like to crosspost my
> answer also to the talk mailing list:
>
> Hello Gerhardus,
>
>
> >In the absence of immediate local presence, is tracing acceptable and not
> wasted effort.
>
> Personally I only do aerial image mapping to a limited extent because I
> fear that I will map wrong objects (e.g. nonexisting buildings, roads)
> because of outdated bing images. I feel much more comfortable to do bing
> mapping when I also do know the surrounding by own survey.
> However, I would follow a pragmatic approach: E.g. If there is no railway
> at all in the map, and you think that it is likely that the railway is
> still there I would go for remote mapping.
>
> Offset Problem:
> Maybe you could compare objects already being mapped on a large scale (
> larger towns ) and only do large scale mapping  like major roads, but no
> micro mapping like lake boundaries on a 50 m scale without having better
> offset information.
>
> Michael
>
>
> Am 01.12.2012 13:59, schrieb Gerhardus Geldenhuis:
>
> Hi
> I have mainly been doing tracing of Bing images in far flung corners of
> the world where I have been. However I have been reading about offset
> problems with Bing imagery and was wondering if this would all be wasted
> work?
>
>  I have mainly been doing work in Zimbabwe and South Africa with work
> being classified as:
>
>    - Tracing and classing buildings
>    - Making lake outlines more accurate. Lake Kariba as an example is a
>    bit rough and ready. This is mainly prep work so I can add marinas and
>    other amenities.
>    - Tracing railway lines and roads in northern Zimbabwe.
>
>
>  I might revisit a number of the places I have edited  and will then be
> able to get some GPS traces, building names etc that I could use to compare
> offset with. But in the meantime is there any other way to determine the
> offset of satellite imagery?
>
>  So to summarize my questions:
>
>    - In the absence of immediate local presence, is tracing acceptable
>    and not wasted effort.
>    - Is there a reliable way to determine offset in a specific location
>    without GPS track data
>
> Regards
>
>  --
> Gerhardus Geldenhuis
>
>
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-- 
Gerhardus Geldenhuis
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