[fdo-users] view scale

[Artyom]

My provider must for both types.

If it is possible to give me an information about how to get it for
features?

Thank you


Traian Stanev wrote:
> 
> 
> You cannot get the screen extent from inside an FDO provider, unless your
> data is raster. Is your data raster?
> 
> 
> If your data is vectors, you could add a custom function that can be used
> with a Select command to pass such arguments (like raster providers do),
> however, you would need to ensure that FDO clients like Map and MapGuide
> in turn use this custom function when requesting data from your provider.
> 
> 
> Traian
> 
> 
> 
>> -----Original Message-----
>> From: fdo-users-bounces at lists.osgeo.org [mailto:fdo-users-
>> bounces at lists.osgeo.org] On Behalf Of Artyom
>> Sent: Monday, February 18, 2008 11:40 AM
>> To: fdo-users at lists.osgeo.org
>> Subject: RE: [fdo-users] view scale
>>
>>
>> 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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>> >>
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