TUTORIAL : Terrain Data Creation
Creating terrain data for arcAstroVR requires GeoTiff data for wide-area terrain, GeoTiff data for narrow-area terrain, geoid data, texture data, etc. as original data, and is created using the terrain maker for arcAstroVR plug-in for QGIS.
Setting up of wide-area terrain data and narrow-area terrain data
Please refer to Obtain wide-area terrain data (30m mesh, JAXA ALOS) for obtaining and integrating wide-area terrain data, and Obtain narrow-area terrain data (5m mesh, GSI) for obtaining and integrating GeoTiff data for narrow-area terrain.
Drag and drop the GeoTiff of the integrated wide-area terrain data into the layer column on the left of QGIS to setting up it, and name it 30mDEM .
Drag and drop the GeoTiff of the integrated narrow-area terrain data into the layer column on the left of QGIS to setting up it, and name it 5mDEM .
Obtain and setting up geoid data
To know the exact undulations in 3D space, not only elevation data but also geoid data is required. The geoid represents the mean sea level fluctuation from the earth's ellipsoid due to local gravity, and takes a variation value of approximately -67m to +79m. However, an area of a few kilometers does not show significant height changes due to the geoid. Therefore, even without geoid data, there is no significant difference in relative height difference in practical use, but for more precise terrain representation, geoid data should be taken into account.
Geoids are also available free of charge in a variety of places. GSI publishes precise geoids of Japan in xml format, but the GeoTiff data published by AgiSoft is easy to use as a GeoTiff that covers the entire globe from the beginning.
Open AgiSoft's Geoid page. (https://www.agisoft.com/downloads/geoids/ )
Download the GeoTiff data for EGM2008 1'geoid model(EPSG::1027) from the Global Models.Geoid data files vary depending on the time of observation and measurement accuracy. In the case of a flat area with little gravitational fluctuation, the EGM84 30' geoid model (EPSG::5203) with a resolution of 30' units may be sufficient. On the other hand, for mountainous areas with complex high mountain ranges, the EGM2008 1' geoid model (EPSG::1027) with a resolution of 1' may be preferable.
After downloading the GeoTiff of the desired resolution, drag and drop the file into the layer column on the left of QGIS to setting up it and name it egm2008-1 .
Creation of terrain data for arcAstroVR
Terrain data for arcAstroVR is created using the terrain maker for arcAstroVR plug-in for QGIS. In this explanation, wide-area terrain data and narrow-area terrain data are created at the same time, but each can be created independently.
The following explanation assumes that 30mDEM GeoTiff data for wide area topography, 5mDEM GeoTiff data for narrow area topography, egm2008-1 Geoid GeoTiff data, and GoogleMaps (photo) texture data are already set in the Layer column of QGIS.
Click terrain maker for arcAstroVR in the QGIS icon bar.For information on installing terrain maker for arcAstroVR , please refer to the tutorial Installation Procedure for QGIS Terrain Generation Plugin .
緯度,経度 field. In the example, we have entered the center location of the Yoshinogari Ruins North Inner Wall (33.326902°, 130.386323°).Specify wide-area terrain data 30mDEM for the 基本地形用DEMレイヤ .
Specify Geoid data egm2008-1 for the 基本地形用Geoidレイヤ .
Specify Texture data GoogleMaps (photo) for the 基本地形用Textureレイヤ .
Specify narrow terrain data 5mDEM for the 詳細地形用DEMレイヤ .
Specify Geoid data egm2008-1 for the 詳細地形用Geoidレイヤ .
Specify Texture data GoogleMaps (satellite photo) for the 詳細地形用Textureレイヤ .
Enter 5.0 in the メッシュ(m) .
Specify a Dataset Folder for 保存先 In the example, /Users/iwashiro/Desktop/terrain is specified.
Click OK button to start creating terrain data for arcAstroVR.*Please note that it takes a very long time to create the terrain data. It takes about 1 hour for basic terrain and 1 minute for detailed terrain.
The terrain data (terrain00.raw to terrain33.raw) and texture data (terrain00.jpg to terrain33.jpg) for arcAstroVR will be created in the destination folder location. The data is stored in the "terrain" folder of the dataset.