View source for Arc Extract Breakline from DEM

=Introduction=
This page outlines the method used to take a line feature class, and extract elevations from DEM for input to TUFLOW breaklines.  This is useful if you have a hydraulic control, for example a road embankment that you want to ensure is represented in the model.  In this method the elevations will be extracted from the DEM.  If detailed survey exists this should be used.  This can also be used to process a thalweg / creek centre line.
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TUFLOW breaklines (2d Z Shape), are a mixture of line and point feature classes.  This allows points to be deleted, without deleting the vertices along the line.  The process of converting a line feature class, to a point feature class and extracting the elevation.  Is a multiple step process and we are looking to implement a python script to automate this.  There are two ways of doing this:<br>
'''Method 1'''
# Convert line vertices to points
# Extract elevations directly from DEM
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This method requires that the line has been digitised at the high or low point that you are trying to represent. If the vertex on the line, is not at the crest of the ridge, the elevation may be slightly out.<br>
'''Method 2'''<br>
Method 2 creates a buffer around each points and can be used to extract the maximum, minimum or average elevation from the DEM within this buffer.  This ensures that the control is represented, even if the line does not follow the levee crest or centreline perfectly. The steps involved are:
# Convert line vertices to points
# Create a buffer around each point (specified buffer distance)
# Extract desired elevation statistic (max, min, mean) for each region
# Assign elevation from buffer to point

The steps involved in each method are detailed below.
=Method 1 (point inspection)=
<ol>
<li>The first step is to create a point feature class from the line, to do this follow the method outlined in the <u>[[Arc_Lines_to_Points | convert lines to points tip.]]</u></li>
<li>To inspect the elevations at each of the points, follow the method outlined in the <u>[[Arc_Assign_DEM_Value_to_Points | this Arc GIS Tip]].</u>  This will create a new point feature class which contains all of the original attributes, as well as the raster value.
<li>TUFLOW uses the elevation in the '''Z''' attribute, to update this, open the attribute table, right click on the Z attribute and select ''Field Calculator''.</li>
<li>In the dialogue, simply double click on the raster value attribute.</li>
[[File:Arc Breaklines from DEM 02.jpg|400px]]
</ol>

=Method 2 (region inspection)=
<ol>
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