[Gvsig_english] BUG: gvSIG 1.9 (Build 1253) Image Filtering
Benjamin Ducke
benjamin.ducke at oxfordarch.co.uk
Thu Dec 17 13:23:51 CET 2009
A projection does just what the name says: it projects points from a
3D position on a curved surface to a 2D position on a cartesian
(orthogonal) coordinate grid.
Datum + Projection + CRS = SRS
However, in most GIS user interfaces: SRS = Projection
Ben
----- Original Message -----
From: "Simon Cropper (Botanicus Australia Pty Ltd)" <scropper at botanicusaustralia.com.au>
To: "Users and Developers mailing list" <gvsig_internacional at listserv.gva.es>
Sent: Thursday, December 17, 2009 1:09:58 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
Subject: Re: [Gvsig_english] BUG: gvSIG 1.9 (Build 1253) Image Filtering
Ben,
So your definition of projection is limited to the visual 2D
representation of a 3D sphere. Isn't this a datum-coordinate combo as I
stated?
Cheers Simon
Simon Cropper
Botanicus Australia Pty Ltd
PO Box 160, Sunshine, Victoria 3020.
P: 9311 5822. M: 041 830 3437.
mailto: scropper at botanicusaustralia.com.au
<mailto:scropper at botanicusaustralia.com.au>
web: www.botanicusaustralia.com.au <http://www.botanicusaustralia.com.au>
Benjamin Ducke wrote:
> And here comes the artillery:
>
> Coordinate (reference) system (CRS) = a mathematical convention for describing locations relative
> to a defined origin (e.g. Cartesian: 100m East, 200m North, Geographic: lat and long).
>
> Datum = a precise description of the origin of a geodetic system, nowadays this often includes
> a mathematical transformation type and its parameters to convert measurements from
> a foreign system into the system for which the datum is defined (e.g. Potsdam datum).
>
> Projection = a mathematical formula and its parameters that allows you to literally
> project "natural" locations on the Earth's curved 3D surface to a plane for display on
> e.g. a 2D map or monitor. An approximation model of Earth's geoid shape ("Ellipse") is
> also needed for this to work.
>
> Spatial reference system (SRS) or geodetic reference system: the whole bunch of those
> components together. This is what a GIS menu entry usually refers to, even if it is
> labelled "projection".
>
> ... never mind what the GUIs tell you!
>
> Ben
>
>
> ----- Original Message -----
> From: "Simon Cropper (Botanicus Australia Pty Ltd)" <scropper at botanicusaustralia.com.au>
> To: "Users and Developers mailing list" <gvsig_internacional at listserv.gva.es>
> Sent: Thursday, December 17, 2009 12:49:06 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
> Subject: Re: [Gvsig_english] BUG: gvSIG 1.9 (Build 1253) Image Filtering
>
> Ben & Sergio,
>
> Thanks for your understanding. Feel a bit stupid now I look at the
> dialog box. Pretty obvious when you have your head in gear.
>
> Ben. I'll bite. Enlighten me on the distinction between projection &
> coordinate system.
>
> OK, here I go again, potentially making myself look stupid...
>
> coordinate system = northing-easting, lat-long (MGA55, AMG53)
> datum = framework used to reference the coordinate system (GDA94, AGD66)
> projection = particular datum-coordinate system combo (e.g. GDA94 MGA55,
> GDA94 lat/long, AGD66 AMG53, etc)
>
> Should I duck for cover?
>
> Cheers Simon
>
> Simon Cropper
> Botanicus Australia Pty Ltd
> PO Box 160, Sunshine, Victoria 3020.
> P: 9311 5822. M: 041 830 3437.
> mailto: scropper at botanicusaustralia.com.au
> <mailto:scropper at botanicusaustralia.com.au>
> web: www.botanicusaustralia.com.au <http://www.botanicusaustralia.com.au>
>
>
>
> Benjamin Ducke wrote:
>
>> It's OK Simon, we forgive you now ;)
>>
>> The problem with GIS is that the user interfaces are often designed
>> by people who are not actually cartographers or geoscientists.
>> Let's not even get started about the way the terms "projection"
>> or "coordinate system" are used in GIS...
>>
>> Ben
>>
>> ----- Original Message -----
>> From: "Simon Cropper (Botanicus Australia Pty Ltd)" <scropper at botanicusaustralia.com.au>
>> To: "Users and Developers mailing list" <gvsig_internacional at listserv.gva.es>
>> Sent: Thursday, December 17, 2009 12:16:47 PM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
>> Subject: Re: [Gvsig_english] BUG: gvSIG 1.9 (Build 1253) Image Filtering
>>
>> Ben,
>>
>> I agree. In cartographic terms it is correct. It should stay that way,
>> but as you stated other packages don't express these ranges correctly
>> and newbies to gvSIG, like myself, misunderstand the dialog box and post
>> a thread. Some sort of reminder or warning right next to the input box
>> would be a timely reminder.
>>
>> Cheers Simon
>>
>> Simon Cropper
>> Botanicus Australia Pty Ltd
>> PO Box 160, Sunshine, Victoria 3020.
>> P: 9311 5822. M: 041 830 3437.
>> mailto: scropper at botanicusaustralia.com.au
>> <mailto:scropper at botanicusaustralia.com.au>
>> web: www.botanicusaustralia.com.au <http://www.botanicusaustralia.com.au>
>>
>>
>>
>> Benjamin Ducke wrote:
>>
>>
>>> Please keep it that way. It's perfectly correct in cartographic
>>> terms. The fact that all other GIS have taught their users wrong
>>> terminology does not change that.
>>>
>>> Ben
>>>
>>> ----- Original Message -----
>>> From: "Sergio Clark" <sergio.clark at iver.es>
>>> To: "Users and Developers mailing list" <gvsig_internacional at listserv.gva.es>
>>> Sent: Thursday, December 17, 2009 9:58:23 AM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna
>>> Subject: Re: [Gvsig_english] BUG: gvSIG 1.9 (Build 1253) Image Filtering
>>>
>>> Hi,
>>>
>>> I don't think this is a bug. Now both raster and vector layers work the
>>> same way regarding the scale range of visualization (we homogenized the
>>> text in both pannels inside 'Properties').
>>>
>>> I mean, "Don't show layer when the scale is greater than 1:100" means
>>> that it won't be displayed when scale is 1:99, because second one is
>>> "greater scale" than first one (minor denominator, but major scale). And
>>> it's the same for "less than...".
>>>
>>> Regards,
>>> Sergio.
>>>
>>>
>>>
>>> Sergio Clark
>>> Equipo gvSIG
>>> IVER T.I., S.A.
>>> www.iver.es
>>> www.gvsig.com
>>>
>>>
>>>
>>> Rahkonen Jukka escribió:
>>>
>>>
>>>
>>>> Hi,
>>>>
>>>> Maybe this is the old question about which scale is big and which is
>>>> small? Compare scales 1:10 and 1:100. Hundred is bigger number than ten,
>>>> but because it appears in the denominator the scale 1:100 is smaller
>>>> than 1:10.
>>>>
>>>> Perhaps it would be more clear to put the words in another way: "Do not
>>>> show this layer if scale denominator is bigger/smaller than".
>>>>
>>>> -Jukka Rahkonen-
>>>>
>>>> Simon Cropper wrote:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>> Hi Guys,
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>>> I have Noted a bug in the program.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>>> If you set the scale range for a raster file the "is above 1:????" and
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>>> "is below 1:????" is around the wrong way.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>>> If you set "Do not show this layer if the scale is above 1:100000",
>>>>>
>>>>>
>>>>>
>>>>>
>>>> the
>>>>
>>>>
>>>>
>>>>
>>>>> image only appears if the scale exceeds 1:100,000.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>>> So either the text is wrong or the filter condition is around the
>>>>>
>>>>>
>>>>>
>>>>>
>>>> wrong way.
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>>>>
>>>>
>>>>
>>>>
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