Terrain height: Difference between revisions

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{{learned|about Terrain Height|how terrain height is implemented in the {{software}}|how to add or remove terrain height with the terrain height brush panel|how to change terrain height}}
#REDIRECT [[Elevation model]]
 
==Terrain height==
: Terrain height is the whole of differences of terrain elevation in a given area, the quantitative measurement of vertical elevation change in a landscape. Terrain is used here as a general term in physical geography, referring to the lay of the land. This is usually expressed in terms of the elevation, slope, and orientation of terrain features. Terrain height - as element of a terrain - affects surface water flow and distribution. Over a large area, it can affect weather and climate patterns.
 
: In overlays, the user can select two types of elevation, the digital terrain model (DTM) and digital surface model (DSM). A DTM represents the bare ground surface without any objects like plants and buildings. In contrast; a DSM represents the earth's surface including all objects (e.g. houses, trees, etc.) on it.
 
: [[File:DTM_DSM.png|400px]]
 
: View original file here:[https://commons.wikimedia.org/wiki/File:DTM_DSM.svg]
 
==Terrain height in the {{software}}==
 
#REDIRECT [[Terrain height]]
{{learned|what an elevation model is|what is considered part of the {{software}}'s elevation model|how the {{software}} generates an elevation model|how to enrich or replace the elevation model with your own data}}
{{stub}}
{{being updated}}
==What is an elevation model==
[[File:DTM_DSM.png|thumb|200px|left|Source: https://commons.wikimedia.org/wiki/File:DTM_DSM.svg]]
An elevation model, also known as a Digital Surface Model (DSM) or Digital Terrain Model (DTM) as appropriate, is a model representation of terrain heights; the quantitative measurement of vertical elevation change in a landscape. On a small scale, differences in terrain height can affect shade and water distribution. On a larger scale, terrain height has an effect on weather and climate patterns.{{clear}}
 
==How is the elevation model implemented in the {{software}}==
In the {{software}}, the elevation model offers terrein heights representation as both a DTM and as a DSM. Specifically, it is a 2-dimensional grid with values indicating the terrain height in meters relative to {{datum}}. Terrain in this context meaning the soil and everything below it. Features such as [[Construction]]s are explicitly not a part of the DTM, but are a part of the DSM. In locations with [[Water (Terrain Attribute)|water]], the elevation model follows the bottom of the water body for both the DTM and the DSM.
 
The [[3D World]] visualizes the elevation model inherently as the bottom plane upon which all other features, such as [[Construction]]s, are placed. Changes in terrain height are similarly changes in the height of that plane.
 
===Heightmap Overlay===
{{main|Heightmap Overlay}}
More insight into the elevation model can be provided by adding the [[Heightmap Overlay]], which is a [[Grid Overlay]] showing the (average) height of the terrain per [[grid cell size|grid cell]].
 
 
==Elevation model generation==
[[File:Ahn.jpg|300px|thumb|right|The [[Advanced options (New project Wizard)|advanced options]] allow you to select data sources and resolutions for the elevation mode.]]
In the Netherlands, the following data sources are used to construct the elevation model:
 
{|class=wikitable
! Name
! Type
! Detail
! Description
! Source
|-
| ESRI DTM
| DTM
| 3m by 3m
| Dataset supplied by Rijkswaterstaat to ESRI, based on AHN2.
| http://www.arcgis.com/home/item.html?id=58a541efc59545e6b7137f961d7de883
|-
| AHN DSM
| DSM
| 0.5m by 0.5m, 1m by 1m, or 2.5m by 2.5m, depending on [[Advanced options (New project Wizard)|selected options]].
| Raw data from [http://www.ahn.nl Actuele Hoogte Bestand]
| http://www.arcgis.com/home/item.html?id=55df27e20c0d42e3a8bd48bc74c5c8cc (AHN2) or http://www.arcgis.com/home/item.html?id=b87c68ea246c4b17807cdad486279a47 (AHN3)
|-
| AHN DTM
| DTM
| 0.5m by 0.5m, 1m by 1m, or 2.5m by 2.5m, depending on [[Advanced options (New project Wizard)|selected options]].
| Interpolated (surface level) data based on [http://www.ahn.nl Actuele Hoogte Bestand]
| http://www.arcgis.com/home/item.html?id=9d62ff8889ba41b2b712a68c7493bd16 (AHN2) or http://www.arcgis.com/home/item.html?id=9d62ff8889ba41b2b712a68c7493bd16 (AHN3)
|-
| Features
|
|
| Presence of features of the built environment
| https://www.pdok.nl/introductie/-/article/basisregistratie-grootschalige-topografie-bgt- (BGT) or https://www.pdok.nl/introductie/-/article/basisregistratie-topografie-brt-historie (Top10NL)
|}
 
===DTM (Terrain height)===
* The ESRI DTM is resampled to the same resolution as the AHN DTM and AHN DSM.
* The AHN DTM serves as the base data for the resulting elevation model DTM.
* In locations where the AHN DTM has NO_DATA values (such as waterbodies), the ESRI DTM is used.
* Optionally, if [[Advanced options (New project Wizard)|the option for applying thresholds]] is selected, the AHN DSM heights are used instead of the so far determined DTM heights, if the difference between the two does not exceed a certain threshold. The following features can have the DSM heights applied instead:
** Bare land
** Roads
** Crop fields/agriculture
 
===DSM (Construction height)===
For [[Construction]]s, the average height of the AHN DSM is determined for the [[Construction]]'s footprint polygon. That average height of the AHN DSM is then determined to be the height of the [[Construction]].
 
Using image recognition techniques, the footprint polygon of the [[Construction]]s may be split up into multiple [[Construction section]]s, each with their own polygon. The AHN DSM's average height is then determined per individual section, so that the variability in the rooftops of the [[Construction]] can be taken into account.
 
The resulting [[Construction]] heights are not made part of DTM. Instead, they are stored as properties of the [[Construction]]s in the [[Project]].
===Water===
In locations with water features, the water's depth is "carved" into the DTM as determined up to this point. The following parameters are used to do so:
* The [[water depth m (Terrain Attribute)|default water depth]] of the determined [[Terrain Type]] of the water feature is used.
* The [[angle of repose (Terrain Attribute)|angle of repose]] of the underground [[Terrain Type]] present at or near the sides of the water feature.
Starting from the edges of the polygon of the water feature, a downward slope is created at the determined angle of repose. The downward slope continues until either it meets the slope generated from the other end, or it reaches the determined default depth relative to the DTM. This means that thin waterrways will not be as deep as their default water depth allows them to be, and that large water bodies are likely to have flat water bottoms.
 
==Elevation model generation (outside the Netherlands)==
{{stub|type=section}}
 
==How-to's==
* [[How to change how the default elevation model is generated]]
* [[How to import a GeoTIFF as elevation model]]
* [[How to import a GeoJSON to change the elevation model]]
* [[How to import waterways]]
* [[How to export the elevation model]]
* [[How to use the terrain height brush in selection mode]]
* [[How to use the terrain height brush in live sculpting mode]]
 
==See also==
* [[Terrain]]
* [[Elevation model (Water Overlay)]]
 
==Changing terrain height==
There are two options to change terrain height. One is to import a raster file with the new terrain height and the other option is to draw in the {{software}} where the terrain should be changed and to which height.
 
===Importing a terrain height dataset===
See [[How_to_import_terrain_height_data| how to import terrain height data]].
 
<br clear=all>
 
<!--
==Adding or removing terrain height==
{{Editor location|Terrain elevation}}[[File:TerrainHeightBrushPanel1.jpg|thumb|right|200px|Drawing Terrain Height in 3D world]]
: When a project is created in the {{software}}, all terrain is flat. To add relief in the form of terrain height, a specific tool is available - the height tool brush.
 
===The Terrain Height Brush panel===
{{Editor location|Terrain elevation}}
: Below is an image of the Terrain Height Brush Panel. This tool looks like the more common [[brush|brush panel]], but is adjusted to be able to draw in terrain height in the [[3D World|3D world]].
[[File:TerrainHeightBrushPanel2.jpg|left|frame|200px|Terrain Height Brush Panel]]<br clear=all>
====Start/ stop drawing====
: ''The top button on the panel is called "Start Drawing" by default when loading the panel. This first button (de)activates the Terrain Height brush panel, by selecting the button named "Start Drawing" the rest of the options become available on the panel. With the brush panel activated, the user can start "painting". Selecting this button again - now named "Stop Drawing" - deactivates the panel, greying out the options.''
<gallery mode="nolines">
File:TerrainHeightBrushPanel3.jpg|Terrain height brush panel inactive
File:TerrainHeightBrushPanel2.jpg|Terrain height brush panel active
</gallery>
 
====Radius====
: ''The first slider from the top is called "Radius". The radius slider refers to how big the area is that the cursor will affect when changing the terrain's height. The more to the right the slider is positioned, the larger the area of effect is.''
<gallery mode="nolines">
File:TerrainHeightBrushPanelRadius.jpg|Terrain height brush panel radius slider
</gallery>
 
====Press====
: ''The second slider from the top is called "Press" - for "Pressure". The press slider refers to how fast the area will be affected when changing the terrain's height. The more to the right the slider is positioned, the faster the area will adjust, making it possible to quickly alter terrain. If the slider is positioned more to the left side, the height effect can be finely adjusted.''
<gallery mode="nolines">
File:TerrainHeightBrushPanelPress.jpg|Terrain height brush panel press slider
</gallery>
====Brush Types====
----
 
=====Flatten=====
: ''The brush type button on the right of the "Clear" button is called "Flatten". With the "Flatten" button, any area that the brush 'paints' will be flattened while maintaining most of its height. This is useful when placing constructions on elevated or lowered terrain, as constructions can only be placed on flat surfaces.''
<gallery mode="nolines">
File:TerrainHeightBrushPanelFlatten.jpg|Terrain height brush panel flatten button
</gallery>
 
=====Raise=====
: ''The brush type button below the "Clear" button is called "Raise". With the "Raise" button any area that the brush 'paints' will be raised in elevation, in order to create terrain height, such as hills or other relief.
<gallery mode="nolines">
File:TerrainHeightBrushPanelRaise.jpg|Terrain height brush panel raise button
</gallery>
 
=====Lower=====
: ''The brush type button below the "Flatten" button is called "Lower". With the "Lower" button any area that the brush 'paints' will be lowered in elevation, in order to create terrain effects such as valleys or even open (polder) water.''
<gallery mode="nolines">
File:TerrainHeightBrushPanelLower.jpg|Terrain height brush panel lower button
</gallery>
----
 
====Reset Changes====
: ''The next button is called "Reset Changes". This button makes it possible to quickly undo any changes. With this button any changes that are not applied yet will be reverted.''
<gallery mode="nolines">
File:TerrainHeightBrushPanelResetChanges.jpg|Terrain height brush panel reset changes button
</gallery>
 
====Apply Changes====
: ''The last button, on the bottom of the panel, is called "Apply Changes". This button confirms changes made with the terrain height brush. After applying these changes it is not possible to revert them anymore. ''
<gallery mode="nolines">
File:TerrainHeightBrushPanelApplyChanges.jpg|Terrain height brush panel apply changes button
</gallery>
-->
 
===Drawing terrain height===
{{Editor location|Terrain elevation}}
{{Editor steps|title=change terrain height|Open the Terrain Height Brush Panel|Select "Start Drawing"|Adjust the Radius and Press sliders as desired|Select the brush type Raise, Flatten or Lower|Adjust terrain height by pressing and holding the left mouse button while drawing in the 3D world| Confirm the changes by selecting "Apply changes"}}
 
<!--===Removing terrain height===
{{Editor location|Terrain elevation}}
{{Editor steps|title=remove terrain height|Open the Terrain Height Brush Panel|Select "Start Drawing"|Adjust the Radius and Press sliders as desired|Select the brush type Clear|Adjust terrain height by pressing and holding the left mouse button while drawing in the 3D world| Confirm the changes by selecting "Apply changes"}}-->

Latest revision as of 09:32, 27 August 2020

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