Drawing - Transfer Heights

The Transfer Heights command takes heights from a surface and transfers them to objects in drawings (points, lines or areas) that overlay that surface. It is a fast and easy way to get the height of a surface at different points. The Transfer Heights command may be thought of as an analog of the Spatial Overlay command designed for use between surfaces and drawings.

 

The Drawing - Transfer Heights menu selection is enabled when the optional Surface Tools extension has been installed and the focus is on a drawing window or on a drawing layer in a map window. If you have not activated the Surface Tools extension with a valid Surface Tools serial number you will not be able to use the Drawing - Transfer Heights command.

 

images\dlg_drawing_transfer_heights.gif

 

Launching the Transfer Heights command in the Drawing menu launches the Transfer Heights dialog.

 

Controls

Source

Choose the surface from which heights will be taken.

Target

Choose the drawing to which heights will be transferred.

[Field]

Choose the name of a field in the target drawing's table to which heights will be transferred. If no columns exist in the target table, a choice of [New Column] will create a new column called Height.

Aggregate heights…

Specify the method used to assign height values to line and area objects, which extend over many different heights:

Average - Assign the average height found in the line or area.

Maximum - Assign the maximum height found in the line or area.

Minimum - Assign the minimum height found in the line or area.

Sum - Assign the sum of heights found in the line or area.

 

Example

 

Suppose we have a drawing of five points showing locations of survey stations in the Montara Mountain region of California. We also have the 1:24K-scale SDTS DEM surface of the region downloaded from the USGS website.

 

images\eg_transfer_heights_01.gif

 

We can show the drawing and the surface together in a map to see where the five points are located relative to the surface.

 

images\eg_transfer_heights_02.gif

 

If we open the drawing's table we can see that so far there are no fields (except for the default ID field) in the table.

 

images\dlg_drawing_transfer_heights.gif

 

Clicking back on the drawing layer to move the focus there, we can launch the Drawing - Transfer Heights dialog with the above values and then press OK. It doesn't matter what we choose for the Aggregate choice since there are no lines or areas in the drawing.

 

images\eg_transfer_heights_03.gif

 

Instantly, a new field called Height will be created in the table and it will be populated with the height of the surface at each point.

 

Comments

 

Although the above example uses terrain elevation, the Transfer Heights command works perfectly well regardless of what data is conveyed by the surface. For example, if we had a surface that showed average temperature the value of average temperature could be transferred as the "height" to objects in the target drawing.

 

The Transfer Heights command is a fast way of noting the height of a surface at points of interest. Simply create a map with the surface and then add a blank drawing layer to the surface. Click with the Insert Point tool to create points where desired and then use Transfer Heights to save the height of the surface at each point into the drawing's table.

 

The Sum option for transfer of heights to areas provides a way of aggregating values from surfaces, if those surfaces have been correctly designed for such uses. It locates all the surface's pixels that lie within an overlying area and sums up the value of the height for each pixel.

 

Sum might be used, for example, in a case where a surface represents the concentration of a toxic material deposited downwind of a hazardous material incident (such as an explosion or fire). If the concentration is given in some value per square meter and we know the size of the pixels used to represent the surface, then the Sum of values for pixels that occur in a given area will be directly related to the total amount of toxic material deposited within that area. If the area represents, say, a lake or other body of water we can find the total amount of toxic material deposited into that lake.

 

Note that since clearly, if the same surface is represented with more pixels (that is, each pixel covers a smaller region) then the Sum will be greater. However, if we pay attention to the size of pixels in use we can re-scale the result as desired by simply multiplying or dividing the resulting Sum.

 

See Also

 

Surface Tools