brind align into tutorials

Author: smathermather

source/tutorials.rst

@@ -820,6 +820,20 @@ For instance, point clouds properties can be modified to show elevation and also
 
 `Learn to edit <https://github.com/opendronemap/docs#how-to-make-your-first-contribution>`_ and help improve `this page <https://github.com/OpenDroneMap/docs/blob/publish/source/tutorials.rst>`_!
 
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+###############
+Alignment Files
+###############
+
+Georeferencing by default is done using GPS or GCPs (if provided).
+
+Starting from ODM ``3.0.2`` people can supply a reference alignment file to georeference the program outputs. The reconstruction will be initially performed using GPS/GCPs and will subsequently be aligned to the reference model via a linear scaling/rotation/shift operation. 
+
+If you supply a file called ``align.laz``, ``align.las`` or ``align.tif`` (single band GeoTIFF DEM) then ODM will automatically detect it and attempt to align outputs to this reference model. If it has another name you can specify using ``--align <path>``.
+
+The alignment file must be created in the base of your project folder. The base folder is usually where you have stored your images. If you are using WebODM or NodeODM, then upload the align file with your images. If resizing your images in WebODM, use an ``align.laz`` or ``align.las`` file instead of a tif.
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+
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 Multi-temporal Datasets
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