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SLD scale denominator unit?

Imran Rajjad
Hi list,

I`m trying to figure out that what are the units used in below
mentioned SLD scale denominators?

<sld:MinScaleDenominator>100</sld:MinScaleDenominator>
<sld:MaxScaleDenominator>3536652</sld:MaxScaleDenominator>

regards,
Imran

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Re: SLD scale denominator unit?

aaime
Imran Rajjad ha scritto:
> Hi list,
>
> I`m trying to figure out that what are the units used in below
> mentioned SLD scale denominators?
>
> <sld:MinScaleDenominator>100</sld:MinScaleDenominator>
> <sld:MaxScaleDenominator>3536652</sld:MaxScaleDenominator>

As far as I remember, whatever the unit of your projection is.
Unless it's in geographic coordinates, in that case the WMS
specification provides a simplified formula that should put
the unit in meters, but it's really quite far away form the
real scale (I think it assumes
the parallels diameter is always equals to the equator one,
but I don't remember exactly).

Cheers
Andrea

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OpenGeo - http://opengeo.org
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Re: SLD scale denominator unit?

Imran Rajjad
Hi,

thanks for your reply, but I could reallu use something more than
assumptions, as I need to do some serious calculations and answering
over this.

What does 100 mean? Does it mean 100 meters or 100 Decimal degrees
horizontal extent? I`m using EPSG:4326

regrds,
Imran

On Thu, Feb 18, 2010 at 12:53 PM, Andrea Aime <[hidden email]> wrote:

> Imran Rajjad ha scritto:
>>
>> Hi list,
>>
>> I`m trying to figure out that what are the units used in below
>> mentioned SLD scale denominators?
>>
>> <sld:MinScaleDenominator>100</sld:MinScaleDenominator>
>> <sld:MaxScaleDenominator>3536652</sld:MaxScaleDenominator>
>
> As far as I remember, whatever the unit of your projection is.
> Unless it's in geographic coordinates, in that case the WMS
> specification provides a simplified formula that should put
> the unit in meters, but it's really quite far away form the
> real scale (I think it assumes
> the parallels diameter is always equals to the equator one,
> but I don't remember exactly).
>
> Cheers
> Andrea
>
> --
> Andrea Aime
> OpenGeo - http://opengeo.org
> Expert service straight from the developers.
>



--
I.R

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Re: SLD scale denominator unit?

aaime
Imran Rajjad ha scritto:
> Hi,
>
> thanks for your reply, but I could reallu use something more than
> assumptions, as I need to do some serious calculations and answering
> over this.
>
> What does 100 mean? Does it mean 100 meters or 100 Decimal degrees
> horizontal extent? I`m using EPSG:4326

WMS scale denominators in EPSG:4326 or any other geographic projections
are useless for serious calculations, by design. The error included
in the simplified formulas is simply enormous.

I'll say more: any computer calculated scale is useless for really
serious calculations because the code is making assumptions on the DPI
or your video to calculate the scale, and today that value can vary
wildly between different monitors

Cheers
Andrea


--
Andrea Aime
OpenGeo - http://opengeo.org
Expert service straight from the developers.

------------------------------------------------------------------------------
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Re: SLD scale denominator unit?

Imran Rajjad
ok I get what your saying! even if it is erroneous , it must have some
relation with the extent of the map

regards,
Imran

On Thu, Feb 18, 2010 at 1:10 PM, Andrea Aime <[hidden email]> wrote:

> Imran Rajjad ha scritto:
>>
>> Hi,
>>
>> thanks for your reply, but I could reallu use something more than
>> assumptions, as I need to do some serious calculations and answering
>> over this.
>>
>> What does 100 mean? Does it mean 100 meters or 100 Decimal degrees
>> horizontal extent? I`m using EPSG:4326
>
> WMS scale denominators in EPSG:4326 or any other geographic projections
> are useless for serious calculations, by design. The error included
> in the simplified formulas is simply enormous.
>
> I'll say more: any computer calculated scale is useless for really
> serious calculations because the code is making assumptions on the DPI or
> your video to calculate the scale, and today that value can vary
> wildly between different monitors
>
> Cheers
> Andrea
>
>
> --
> Andrea Aime
> OpenGeo - http://opengeo.org
> Expert service straight from the developers.
>



--
I.R

------------------------------------------------------------------------------
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Re: SLD scale denominator unit?

Rahkonen Jukka (Tike)
In reply to this post by Imran Rajjad
Hi,

100 means the scale denominator, what is under the line in the scale
ratio, in this case 1:100. And it means that one centimeter on your
screen is something like 100 centimeters in real world.  

The perfect knowledge is in the Symbology Encoding stardard,
downloadable from  http://www.opengeospatial.org/standards/symbol

I suppose you are already reading the document, it was rather easy to
find and you said you are serious.

-Jukka Rahkonen-

Imran Rajjad wrote:

>
> Hi,
>
> thanks for your reply, but I could reallu use something more than
> assumptions, as I need to do some serious calculations and answering
> over this.
>
> What does 100 mean? Does it mean 100 meters or 100 Decimal degrees
> horizontal extent? I`m using EPSG:4326
>
> regrds,
> Imran
>

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SLD scale denominator unit?

unknown

Hi All
i m confusing that if scale denominator ratio is 1:50000 then what is this 50000 means?what is its unit is it meter,cm,mm, ??
the other thing is that when we define maxscaledenominator in our SLD lets suppose i define1:181000
the intervel of zoom which i see in openlayer .
what does the one intervel shows
here i m attaching a image in which intervels of zoom levels are shown what does each intervel means the value of?
here are 13 lines of zoom here
1:181000 divided in 13 lines why not 14 or 12???
plz help me solving this mystry
Regards


 intervels.bmp



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Re: SLD scale denominator unit?

David Winslow-5
In reply to this post by Imran Rajjad
As the "denominator" it is the right-hand side of the scale ratio (items
on the map are at 1:<denominator> their normal size.)  The left hand
side is in screen units (not pixels, but the actual measure of the
feature on screen*) and the right hand side is in real-world units,
which vary with your dataset's projection.

A handy tool to avoid thinking about all these variables is the
OpenLayers preview map.  It is calibrated to make the same assumptions
about display resolution that GeoServer does, so the scale ratios it
displays are usable in GeoServer SLDs.  Just look for the 1:200k (etc)
at the bottom left corner of the map.

* Except, GeoServer can't know anything about the display on the other
end of an HTTP connection, so it just assumes a pixel size, 96DPI iirc.

Hope this helps.

--
David Winslow
OpenGeo - http://opengeo.org/

On 02/18/2010 02:47 AM, Imran Rajjad wrote:

> Hi list,
>
> I`m trying to figure out that what are the units used in below
> mentioned SLD scale denominators?
>
> <sld:MinScaleDenominator>100</sld:MinScaleDenominator>
> <sld:MaxScaleDenominator>3536652</sld:MaxScaleDenominator>
>
> regards,
> Imran
>
>    

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Re: SLD scale denominator unit?

atlefren
In reply to this post by unknown
Re: [Geoserver-users] SLD scale denominator unit?

Not complely clear what you are asking here, but in general the scale
unit is the unit of your crs, ie meter for WGS84 UTM etc, and degrees
for WGS84 latlon (EPSG:4326)

-atle

On 07/29/2010 01:58 PM, SilaKhan wrote:
>
> Hi All
> i m confusing that if scale denominator ratio is 1:50000 then what is this
> 50000 means?what is its unit is it meter,cm,mm, ??
> the other thing is that when we define maxscaledenominator in our SLD lets
> suppose i define1:181000
> the intervel of zoom which i see in openlayer .
> what does the one intervel shows
> here i m attaching a image in which intervels of zoom levels are shown what
> does each intervel means the value of?
> here are 13 lines of zoom here
> 1:181000 divided in 13 lines why not 14 or 12???
> plz help me solving this mystry
> Regards
>
>
>    http://old.nabble.com/file/p29295693/intervels.bmp intervels.bmp
>
>
>
>
>   


--
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Utvikler
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tlf: 45 27 86 89
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Re: SLD scale denominator unit?

unknown
In reply to this post by Imran Rajjad
hnm thanks for ur suggestion ,but if u got it what m actually want to know then plz tell me that the extent of map has what relation with these zoom intervels??bbox of map extent ???n what would be the inrvel measure unit?? plz let me clear all these
thanks
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