Cartographic Skills - Mod 10
This week we learned about different types of 3D data and visualization techniques. The first part of this three part assignment was done in Esri's Virtual Training. The two broad categories of data used in 3D Analyst are surfaces, such as rasters, terrain data sets, or Triangulation Irregular Networks (TINs) and 3D features, features with discrete boundaries such as buildings, wells or roads. Some 2D data can also be used. The difference between 2D and 3D is that 3D has a z-value. The z-value is a value represented on the z-axis in a three-dimensional x,y,z coordinate system.
The z-value does not only represent elevation, it can also be used to visualize other attributes such as population or cost. In one of our later exercises we extruded land parcels based on the property value as the z-value. The more valuable the property, the taller it appears.
2D spatial data can be displayed in 3D perspective as long as you have a surface layer with elevation values and the same extent as your 2D data. One of the techniques used to accomplish this is setting the base heights. You start with a surface for your study area, such as an elevation raster, and set its base heights, turn on shading and choose symbology. You may then drape your 2D feature class on top of the topography using the elevation surface to set the base heights for your feature class. These steps are all done through the layer properties.
Base heights establish the elevations of surface locations and features. It is what tells 3D Analyst the elevations values of layers and their features. Shading and symbology increase the perception of depth, enhancing details within the topography.
Other techniques for enhancing 3D views are setting vertical exaggeration, illumination and background color. These techniques are all scene properties rather than layer properties. They will affect the whole scene rather than one layer or another. Vertical exaggeration is used to amplify the surface, emphasizing subtle changes when the horizontal extent is significantly greater than the amount of vertical change. Illumination can add realism such as season or time of day by controlling the position of the light source as though it were the sun. Relief effects are harder to distinguish in shadow so changing the position and angle of the light source can help to emphasize them. Background also helps to add realism to the scene.
Extrusion is a simple technique used to create 3D symbology from 2D features. The process stretches a flat 2D shape vertically to create a 3D object. Extrusion can also be applied negatively as in the case of wells, basements, pilings or other underground features. Extrusion is typically used to set heights for features, such as buildings, but it can also be used to visualize other attributes such as populations or cost in 3D perspective basing the z-value on a value other than elevation as discussed earlier.
The second part of our assignment was to actually convert a 2D building layer to a 3D building layer. We started with a building polygon layer that needed elevation data and a raster layer that contained elevation data. To add the raster elevation data to the building polygons we started using the Create Random Points tool to generate random points within the building shapefile so we could then add the elevations information to those points using the Add Surface Information tool. Once we had our z-value we then used the Summary Statistics tool to generate a single elevation value for each building then joined the Mean Z-value to the building footprint layer. With this done we then had all the data we needed to create a 3D image in ArcScene by extruding the features in our building layer to the Mean Z-value we created in previous steps. With this done we converted the data to a KML file to be shared on Google Earth. Viewing this assignment in Google Earth was pretty cool.
Part III of our assignment was to compare and contrast the 2D and 3D versions of Minard's map of Napoleon's Russian Campaign of 1812. I found the 3D map to be pretty cool and liked some of the added information that was available in the display that wasn't available in the 2D version, but all in all, for the general population I thought the 2D map was still the most useful. All the information it contained was right there to be seen. In the 3D version there was always some bit of information that could not be viewed without changing the view a bit. And when you did, some other bit of information disappeared from view. So while I liked the 3D version more, I thought the 2D version to be more usable.
2D spatial data can be displayed in 3D perspective as long as you have a surface layer with elevation values and the same extent as your 2D data. One of the techniques used to accomplish this is setting the base heights. You start with a surface for your study area, such as an elevation raster, and set its base heights, turn on shading and choose symbology. You may then drape your 2D feature class on top of the topography using the elevation surface to set the base heights for your feature class. These steps are all done through the layer properties.
Base heights establish the elevations of surface locations and features. It is what tells 3D Analyst the elevations values of layers and their features. Shading and symbology increase the perception of depth, enhancing details within the topography.
Other techniques for enhancing 3D views are setting vertical exaggeration, illumination and background color. These techniques are all scene properties rather than layer properties. They will affect the whole scene rather than one layer or another. Vertical exaggeration is used to amplify the surface, emphasizing subtle changes when the horizontal extent is significantly greater than the amount of vertical change. Illumination can add realism such as season or time of day by controlling the position of the light source as though it were the sun. Relief effects are harder to distinguish in shadow so changing the position and angle of the light source can help to emphasize them. Background also helps to add realism to the scene.
Extrusion is a simple technique used to create 3D symbology from 2D features. The process stretches a flat 2D shape vertically to create a 3D object. Extrusion can also be applied negatively as in the case of wells, basements, pilings or other underground features. Extrusion is typically used to set heights for features, such as buildings, but it can also be used to visualize other attributes such as populations or cost in 3D perspective basing the z-value on a value other than elevation as discussed earlier.
The second part of our assignment was to actually convert a 2D building layer to a 3D building layer. We started with a building polygon layer that needed elevation data and a raster layer that contained elevation data. To add the raster elevation data to the building polygons we started using the Create Random Points tool to generate random points within the building shapefile so we could then add the elevations information to those points using the Add Surface Information tool. Once we had our z-value we then used the Summary Statistics tool to generate a single elevation value for each building then joined the Mean Z-value to the building footprint layer. With this done we then had all the data we needed to create a 3D image in ArcScene by extruding the features in our building layer to the Mean Z-value we created in previous steps. With this done we converted the data to a KML file to be shared on Google Earth. Viewing this assignment in Google Earth was pretty cool.
Part III of our assignment was to compare and contrast the 2D and 3D versions of Minard's map of Napoleon's Russian Campaign of 1812. I found the 3D map to be pretty cool and liked some of the added information that was available in the display that wasn't available in the 2D version, but all in all, for the general population I thought the 2D map was still the most useful. All the information it contained was right there to be seen. In the 3D version there was always some bit of information that could not be viewed without changing the view a bit. And when you did, some other bit of information disappeared from view. So while I liked the 3D version more, I thought the 2D version to be more usable.
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