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README.html
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<h2>Accuracy Assessment</h2>
<h4>Accuracy Assessment plugin for QGIS 2.0</h4>
<p>by Jared Kibele </p>
<p>Graduate Student at <a href="http://www.marine.auckland.ac.nz/en/about/our-institute/leigh-marine-laboratory.html">Leigh Marine Lab</a>, <a href="https://www.auckland.ac.nz/en.html">University of Auckland</a></p>
<p><a href="mailto:[email protected]">[email protected]</a></p>
<p>This plugin calculates an error matrix from two raster datasets and
outputs a CSV file that can be loaded into a spreadsheet (LibreOffice
Calc, or MicroSloth Excel). To use it, open your raster layers in
QGis, launch the plugin, select the layer you want to use as the
reference layer, select your comparison layer, and select an output
file with a .csv extension. Click 'OK' then open your .csv file with a
spreadsheet. You should see something like this:</p>
<pre><code>LayerName1 (ref) vs. LayerName2
1 2 3 4 Totals Accuracy
1 618 0 0 3 621 100
2 0 570 2 0 572 100
3 0 0 313 2 315 99
4 0 0 1 383 384 100
Totals 618 570 316 388 1892
Accuracy 100 100 99 99 100
Quantity Disagreement 5
Allocation Disagreement 3
</code></pre>
<p>The classes in this example are integers 1, 2, 3, 4. The reference
layer is laid out in columns (so the reference class labels are
headers in a row) and the comparison map data is laid out in rows (so
the comparison class labels are in the first column). User's accuracy
is in the 'Accuracy' column and producer's accuracy is in the
'Accuracy' row (see Congalton 1991 in references.txt). For a
description of Quantity Disagreement and Allocation Disagreement, see
Pointius and Millones 2011 (references.txt)</p>
<p>Current Limitations: This plugin assumes that raster values of 0 are
unclassified so you can't use 0 as a class value. The plugin also
assumes that you're providing it with two rasters that have the same
pixel size and dimensions. I haven't tested it yet with different
sized rasters. If it doesn't crash with different sized rasters, it
will at least give you useless results. I intend to address that in
future versions. </p>
<p>error<em>matrix.py can do other calculations that are currently not
implemented in the GUI. error</em>matrix.py also has a bunch of
explanitory comments that I won't include here. At some point I'd like
to get the Sphinx documentation working with those comments but that
will have to wait for a future version. error<em>matrix.py also has a
bunch of doc tests. If you want to check that the code is working on
your machine, go to the directory that contains error</em>matrix.py with
the command line and type: "python error_matrix.py" and hit return. If
you get output, please email it to me. If you just get another command
prompt, that means the tests all passed.</p>
<p>This plugin was built with the "Plugin Builder" plugin by GeoApt LLC -
geoapt.com. Thanks GeoApt.</p>
<p>-Jared</p>