WMS:Editing DEM Elevations: Difference between revisions

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While DEMs are simple to use and more commonly available than TIN data, they are more difficult to edit or adjust, primarily because of the number of elevation points that must be changed in order to have a corresponding effect on the drainage characteristics of a watershed. However, there are a few things that can be done, and if kept to a reasonable amount can be powerful in using a DEM for watershed delineation, but you should remember that data can not be manufactured and if you find yourself making numerous edits then you probably need to think about acquiring a different elevation source.
While DEMs are simple to use and more commonly available than TIN data, they are more difficult to edit or adjust, primarily because of the number of elevation points that must be changed in order to have a corresponding effect on the drainage characteristics of a watershed. However, there are a few things that can be done, and if kept to a reasonable amount can be powerful in using a DEM for watershed delineation, but remember that data can not be manufactured. If making numerous unexpected edits, then consider acquiring a different elevation source.


==Editing Single Points==
==Editing Single Points==


A single elevation can be edited by selecting it with the '''Select DEM Points''' tool [[Image:WMSIcon_Select_DEM_Points.png]] and adjusting the z value in the [[WMS:Properties Window|''Edit Window'']], or by double-clicking and bringing up the [[WMS:DEM Point Attributes|''DEM Point Attributes'']]. Other properties such as defining a depression point or manually changing the flow direction can also be edited in the [[WMS:DEM Point Attributes|''DEM Point Attributes'']].
A single elevation can be edited by selecting it with the '''Select DEM Points''' [[File:WMS SelectDEMpointsTool.svg|13 px]] tool and adjusting the z value in the [[WMS:Properties Window|''Edit Window'']], or by double-clicking and bringing up the [[WMS:DEM Point Attributes|''DEM Point Attributes'']] dialog. Other properties such as defining a depression point or manually changing the flow direction can also be edited in the [[WMS:DEM Point Attributes|''DEM Point Attributes'']] dialog.
 
:[[Image:DEMpoint att.png|thumb|none|left|325 px|''DEM Points Attributes'' dialog]]


==Editing Elevations with a Feature Arc==
==Editing Elevations with a Feature Arc==
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The '''Edit Elevations''' command in the ''DEM'' menu is used in conjunction with a selected arc to adjust the elevations of all DEM cells that lie beneath the selected arc. Double-clicking on an arc while in the Terrain Data module will also activate the ''Edit DEM Elevations'' dialog.
The '''Edit Elevations''' command in the ''DEM'' menu is used in conjunction with a selected arc to adjust the elevations of all DEM cells that lie beneath the selected arc. Double-clicking on an arc while in the Terrain Data module will also activate the ''Edit DEM Elevations'' dialog.


[[Image:image77.jpg|thumb|none|left|300 px|''Edit DEM Elevations'' dialog]]
:[[File:EditDEMElevations.png|thumb|none|left|400 px|''Edit DEM Elevations'' dialog]]


The tools at the top of the dialog can be used to select and edit individual locations along the DEM, zoom, pan, refresh, or re-center. There are three ways to edit the elevations:
The tools at the top of the dialog can be used to select and edit individual locations along the DEM, zoom, pan, refresh, or re-center. There are three ways to edit the elevations:


==Select individual DEM points and adjust the elevation==
===Set/Offset all elevations by a given value===
 
Using the '''Select DEM Point''' tool [[Image:WMSIcon_Select_DEM_Point.png]] in the ''Edit DEM Elevations'' dialog you can select a point along the arc and edit the elevation.
 
[[Image:image75.jpg|thumb|none|left|275 px|''DEM Points Attributes'' dialog]]
 
==Set/Offset all elevations by a given value==


You can set all elevations to a constant elevation, or enter an elevation to adjust all selected DEM points up (positive offset) or down (negative offset).
It is possible to set all elevations to a constant elevation, or enter an elevation to adjust all selected DEM points up (positive offset) or down (negative offset).


[[Image:image78.jpg|thumb|none|left|300 px|''Edit DEM Elevations'' dialog showing the ''Constant DEM elevation'' dialog as reached by using the '''Set to constant elevation''' button]]
:[[Image:EditDEMconstant.png|thumb|none|left|400 px|''Edit DEM Elevations'' dialog showing the ''Constant DEM elevation'' dialog as reached by using the '''Set to constant elevation''' button]]


==Linearly Interpolate between first and last elevation==
===Linearly Interpolate between first and last elevation===


You can linearly interpolate all elevations between the first and last elevation. You may wish to edit the first and last elevation first. Of course this will make the channel artificially smooth, but it still may be more realistic for the channel than the irregular nature of DEM elevations as a result. In this fashion you can adjust the channel to slope to a known value.  
It is possible to linearly interpolate all elevations between the first and last elevation. Some may wish to edit the first and last elevation first. Of course this will make the channel artificially smooth, but it still may be more realistic for the channel than the irregular nature of DEM elevations as a result. In this fashion, adjust the channel to slope to a known value. Start with selecting the first and last node, then click the '''Interpolate''' button.


[[Image:image79.jpg|thumb|none|left|300 px|''Edit DEM Elevations'' dialog]]
:[[Image:Edit DEM Elevations Interpolate.png|thumb|none|left|400 px|''Edit DEM Elevations'' dialog after using the '''Interpolate''' button]]


==Related Topics==
==Related Topics==
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{{WMSMain}}
{{WMSMain}}
[[Category:DEM|E]]
[[Category:DEM|E]]
[[Category:WMS Dialogs|E]]
[[Category:DEM Dialogs]]

Latest revision as of 17:10, 2 October 2023

While DEMs are simple to use and more commonly available than TIN data, they are more difficult to edit or adjust, primarily because of the number of elevation points that must be changed in order to have a corresponding effect on the drainage characteristics of a watershed. However, there are a few things that can be done, and if kept to a reasonable amount can be powerful in using a DEM for watershed delineation, but remember that data can not be manufactured. If making numerous unexpected edits, then consider acquiring a different elevation source.

Editing Single Points

A single elevation can be edited by selecting it with the Select DEM Points WMS SelectDEMpointsTool.svg tool and adjusting the z value in the Edit Window, or by double-clicking and bringing up the DEM Point Attributes dialog. Other properties such as defining a depression point or manually changing the flow direction can also be edited in the DEM Point Attributes dialog.

DEM Points Attributes dialog

Editing Elevations with a Feature Arc

The Edit Elevations command in the DEM menu is used in conjunction with a selected arc to adjust the elevations of all DEM cells that lie beneath the selected arc. Double-clicking on an arc while in the Terrain Data module will also activate the Edit DEM Elevations dialog.

Edit DEM Elevations dialog

The tools at the top of the dialog can be used to select and edit individual locations along the DEM, zoom, pan, refresh, or re-center. There are three ways to edit the elevations:

Set/Offset all elevations by a given value

It is possible to set all elevations to a constant elevation, or enter an elevation to adjust all selected DEM points up (positive offset) or down (negative offset).

Edit DEM Elevations dialog showing the Constant DEM elevation dialog as reached by using the Set to constant elevation button

Linearly Interpolate between first and last elevation

It is possible to linearly interpolate all elevations between the first and last elevation. Some may wish to edit the first and last elevation first. Of course this will make the channel artificially smooth, but it still may be more realistic for the channel than the irregular nature of DEM elevations as a result. In this fashion, adjust the channel to slope to a known value. Start with selecting the first and last node, then click the Interpolate button.

Edit DEM Elevations dialog after using the Interpolate button

Related Topics