Difference between revisions of "Arc Extract Breakline from DEM"
(Created page with "=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 hydr...") |
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# Extract elevations directly from DEM | # Extract elevations directly from DEM | ||
<br> | <br> | ||
| − | This method requires that the line has been digitised at the high or low point that you are trying to represent. | + | 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''' | '''Method 2''' | ||
| − | The steps involved are: | + | 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 | # Convert line vertices to points | ||
# Create a buffer around each point (specified buffer distance) | # Create a buffer around each point (specified buffer distance) | ||
# Extract desired elevation statistic (max, min, mean) for each region | # Extract desired elevation statistic (max, min, mean) for each region | ||
# Assign elevation from buffer to point | # 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 create a buffer (region) object around each of the points, firstly open a region feature class. Copy the 2d_zsh_empty_R template to a working directory and rename).</li> | ||
| + | </li>Make the layer | ||
| + | </ol> | ||
| + | =Method 2 (region inspection)= | ||
| + | <ol> | ||
| + | </ol> | ||
Revision as of 05:24, 22 October 2012
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.
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:
Method 1
- Convert line vertices to points
- Extract elevations directly from DEM
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.
Method 2
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)
- The first step is to create a point feature class from the line, to do this follow the method outlined in the convert lines to points tip.
- To create a buffer (region) object around each of the points, firstly open a region feature class. Copy the 2d_zsh_empty_R template to a working directory and rename). Make the layer