[postgis-users] electronic GIS data scale

[erik]

Thanks for you replies.

Yep, the problem is here that we do perform area calculations on these
polygons, so their precision does have a significant impact.
Unfortunately I don't know how to set a criterion of quality for these
features that our data providers could respect. Maybe indeed accuracy in
meters is feasible. Then arises the issue on what margin could be considered
acceptable.

On Tue, Jan 6, 2009 at 3:26 PM, MarkW <mark.wimer at gmail.com> wrote:

> It might be helpful to think about intended uses of your data. You mention
> different digitization methods - if you're concerned that these will impact
> data use, then the methods could go in the metadata or somehow be encoded
> with the data. If you digitized pond boundaries from aerial photos versus
> satellite images, these are different scales - I don't know how you come up
> with a precision for that (but the resolution would factor in), but I would
> think knowing the digitization method would be helpful - i.e. in deciding
> not to do areal calculations below a certain size, etc etc.
>
> Mark
>
> On Tue, Jan 6, 2009 at 8:57 AM, Kristian Thy <thy at 42.dk> wrote:
>
>> On Tue, Jan 06, erik wrote:
>>
>> > This leads to my second question: is it pertinent to talk about scale
>> with
>> > electronic GIS vector data
>>
>> No.
>>
>> > and is *scale* the best way to express the
>> > precision of the data given the different digitization methods used?
>>
>> Probably not.
>>
>> > Is there another way to express precision?
>>
>> I would use "accuracy in metres" (as in, the precision is +/- 5 metres).
>>
>> \\kristian
>>
>>
>
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