[fdo-users] view scale

[Artyom]

Hi again

It seems that I gave not enough information about what I need. 

As mentioned Orest I need the scale such as e.g. 1:20,000. To compute it I
need a full extent of my data, and a current extent of the view. There is a
method FdoSpatialUtility::GetExtents wich fills an extend using a
FdoSpatialCondition. But it is an incorrect method as I understand it does
not return an extend of the current "View". To use formula given by Orest

Scale = sqrt((dbmaxy-dbminy)**2 + (dbmaxx-dbminx)**2) /
sqrt((scrmaxy-scrminy)**2 + (scrmaxx-scrminx)**2) 

I need a screen extent. How can I get it. 

Thanks


Orest Halustchak wrote:
> 
> Hi Artyom,
> 
> Just to clarify, what scale do you need to find? By "view scale" do you
> mean the scale between a map display and ground coordinates (e.g.
> 1:20,000)? If that's really what you mean, then FDO itself has nothing to
> do with that scale. FDO is independent of any map display. Scale would
> have to be computed outside of FDO.
> 
> Thanks,
> Orest.
> 
> -----Original Message-----
> From: fdo-users-bounces at lists.osgeo.org
> [mailto:fdo-users-bounces at lists.osgeo.org] On Behalf Of Artyom
> Sent: Friday, February 15, 2008 9:36 AM
> To: fdo-users at lists.osgeo.org
> Subject: RE: [fdo-users] view scale
> 
> 
> Our data type does not have a measure information. We have type of objects
> that contains some attributive information but mostly it xyz. And to read
> our data not enough to know only current extent.
> About the coordination system can't say anything concrete for now. Because
> I
> need to convert our coordininate system to WKT. now I use only default
> system. I'll research this question a bit later. And by the way my
> provider
> is unmanaged. I couldn't find the entry point for managet connection wich
> could be equivalent to the unmanaged FdoIConnection* CreateConnection ().
> So
> if there is any way to find the scale not using the measure value? Or it
> can
> be done by FDO spatial utilities?
> 
> Thank you for you replies!
> 
> 
> 
> Orest Halustchak wrote:
>>
>> Hi,
>>
>> Artyom, FDO itself deals with data access and has nothing to do with view
>> scales or other view / rendering attributes. That's up to client
>> applications such as MapGuide. The data itself is stored in units defined
>> by the CRS as Maksim points out. Even M (measure) values that might be
>> stored are not tied to any view or view scale. They often are based on
>> ground distance, but can be other units as an application may define.
>>
>> Thanks,
>> Orest.
>>
>> -----Original Message-----
>> From: fdo-users-bounces at lists.osgeo.org
>> [mailto:fdo-users-bounces at lists.osgeo.org] On Behalf Of Maksim Sestic
>> Sent: Friday, February 15, 2008 5:24 AM
>> To: fdo-users at lists.osgeo.org
>> Subject: RE: [fdo-users] view scale
>>
>>
>> OSgeo::FDO::Geometry::DirectPositionImpl has M() property - it represents
>> a
>> Measure related to given coordinate. It's on you to implement parsing of
>> the
>> measure information and extracting something meaningful out of it.
>> Geometry,
>> as it is, doesn't posses a scale - it's unitless by default.
>>
>> On the other hand, FeatureStore may have CRS (Coordinate Reference
>> System)
>> set. CRS establishes soft spatial relation between the "space"
>> (container)
>> and geometric entities placed in it. It's definition does posses measure
>> info, just look under UNITS part of CRS WKT string.
>>
>> Regards,
>> Maksim Sestic
>>
>>
>>
>> Artyom wrote:
>>>
>>> I'm developing an Fdo provider. And I need scale, no metter if it is
>>> MapGuide or AutoDesk Map 3D. Is it possible to get the scale by FDO? Or
>>> my
>>> problem has no solution?
>>>
>>
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