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<div class="moz-cite-prefix">QGIS is configured into a non-earth or
local CRS mode by doing the following (in 2.14):<br>
<br>
1. Turn off 'On the Fly CRS transformation' (Project > Project
Properties > CRS)<br>
2. Ensure that the measurement ellipsoid is set to 'None /
Planimetric' (Project > Project Properties > General)<br>
3. Set the coordinate, distance and area units to 'Map Units'
(Project > Project Properties > General)<br>
<br>
All of these can also be set in the application level settings as
the defaults. QGIS can also be prevented from prompting for a CRS
when loading data that does not have one (QGIS still assigns a
CRS, but essentially it is ignored, so this isn't quite what Simon
was asking for, but close)<br>
<br>
The LocalCoordinateSystemSetter in FME creates custom CRS for
features passing through it, optimising them for equal area or
distance. The same customised CRS could be implemented in QGIS,
what is missing is a tool / plugin that would automatically
generate them.<br>
<br>
Cheers,<br>
<br>
Andy<br>
<br>
On 06/05/2016 17:03, Jonathan Moules wrote:<br>
</div>
<blockquote
cite="mid:15486ce2493.124651bc36007.5565139142377909127@lightpear.com"
type="cite">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<div
style="font-size:10pt;font-family:Verdana,Arial,Helvetica,sans-serif;">There
have been some more knowledgeable responses than mine, but they
do make me ask:<br>
Why doesn't QGIS have a generic Coordinate System for X/Y in
meters (and maybe one in feet for the less developed nations ;-)
)? It would be particularly useful for non-geographical datasets
and would open QGIS up to being used more readily in other
fields.<br>
<br>
Similarly, it could have generic projections for equal area and
equal distance calculations too. I know these are all possible
because FME has all these features.<br>
After all, there's no reason spatial data has to be GEOspatial
data.<br>
<br>
Cheers,<br>
Jonathan<br>
<br>
<br>
<div class="zmail_extra">
<div id="1"><br>
---- On Fri, 06 May 2016 16:28:45 +0100 <b>Lee
Hachadoorian<a class="moz-txt-link-rfc2396E" href="mailto:Lee.Hachadoorian+L@gmail.com"><Lee.Hachadoorian+L@gmail.com></a></b> wrote
---- <br>
</div>
<blockquote style="border-left: 1px solid #0000FF;
padding-left: 6px; margin:0 0 0 5px">
<div>
<div>Simon,
<div><br>
</div>
<div>You *must* specify a projection, but within some
limits, the projection doesn't matter. Basically, if
the GeoTIFF uses units of meters and you want your
distances in meters, you can load the GeoTIFF in *any*
projected CRS that uses meters. An example would be to
use any of the UTM zones. You cannot use a lat-long
CRS such as the default WGS 84, because QGIS will
convert (naively, *not* using great circle distances)
from decimal degrees to meters.</div>
<div><br>
</div>
<div>Once the layer is loaded, all geometry calculations
are done in a Cartesian plane.</div>
<div><br>
</div>
<div>I answered a similar question on <a
moz-do-not-send="true" href="http://GIS.SE"
target="_blank">GIS.SE</a> regarding someone who
wanted to use QGIS to map indoor location data.</div>
<div><br>
</div>
<div><a moz-do-not-send="true"
href="http://gis.stackexchange.com/questions/187699/how-to-create-a-qgis-map-of-unprojected-data"
target="_blank">http://gis.stackexchange.com/questions/187699/how-to-create-a-qgis-map-of-unprojected-data</a><br>
</div>
<div><br>
</div>
<div>Best,</div>
<div>--Lee</div>
</div>
<div><br>
<div>On Fri, May 6, 2016 at 10:12 AM, Jonathan Moules <span><<a
moz-do-not-send="true"
subjmailid="jonathan-lists%40lightpear.com"
href="mailto:jonathan-lists@lightpear.com"
target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:jonathan-lists@lightpear.com">jonathan-lists@lightpear.com</a></a>></span>
wrote:<br>
<blockquote style="margin: 0 0 0 0.8ex;border-left:
1.0px rgb(204,204,204) solid;padding-left: 1.0ex;">
<div>
<div style="font-size: 10.0pt;font-family: Verdana
, Arial , Helvetica , sans-serif;">Hi Simon,<br>
If you know the real-world width and height of
the area covered on the image, could you not
geo-reference it to have lower-left at 0,0, and
then the top-right at the applicable location in
the projection of your choice, and then work
from there?<br>
<br>
The problem is picking an applicable projection.
I can't see any generic "X,Y" projection, let
alone one that is suited to equal-area or
equal-distance in the projections list. They may
exist, I'm just failing to find them. They all
seem to assume they're "somewhere" in the world
(which can be a problem if the data is spatial
but not geographical).<br>
Personally if it's a relatively small area (a
few km across), I'd probably just use a standard
Mercator for the applicable part of the world
probably.<br>
<br>
Cheers,<br>
Jonathan<br>
<br>
<br>
<div>
<div><br>
---- On Fri, 06 May 2016 13:33:47 +0100 <b>simonc8<<a
moz-do-not-send="true"
subjmailid="simoncrombie%40onetel.com"
href="mailto:simoncrombie@onetel.com"
target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:simoncrombie@onetel.com">simoncrombie@onetel.com</a></a>></b>
wrote ---- <br>
</div>
<div>
<div>
<blockquote style="border-left: 1.0px
solid rgb(0,0,255);padding-left:
6.0px;margin: 0 0 0 5.0px;">
<div>I want to use QGIS to make
measurements such as distances and
angles on a<br>
flat scaled image which I have as a
georeferenced tiff. I don't want to
use<br>
any projection - just a
straightforward orthogonal linear
scale in metres.<br>
QGIS seems to require that I choose a
projection. What would be the best<br>
choice for my needs? Can I make a
custom projection with no ellipsoid or<br>
datum?<br>
<br>
If I import my geotiff and don't
specify a projection QGIS assumes my
units<br>
are in degrees rather than metres,
which will make measurement of
distances<br>
and angles inaccurate.<br>
<br>
Grateful for assistance. <br>
<br>
<br>
<br>
--<br>
View this message in context: <a
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<br>
<br>
<div><br>
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-- <br>
<div>Lee Hachadoorian<br>
Asst Professor of Geography, Dartmouth College<br>
<a moz-do-not-send="true"
href="http://freecity.commons.gc.cuny.edu/"
target="_blank">http://freecity.commons.gc.cuny.edu/</a></div>
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<p><br>
</p>
<pre class="moz-signature" cols="72">--
Andy Harfoot
GeoData Institute
University of Southampton
Southampton
SO17 1BJ
Tel: +44 (0)23 8059 2719
Fax: +44 (0)23 8059 2849
<a class="moz-txt-link-abbreviated" href="http://www.geodata.soton.ac.uk">www.geodata.soton.ac.uk</a>
</pre>
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