TUTORIAL : Obtain wide-area terrain data (30m mesh, JAXA ALOS)

The terrain data for arcAstroVR uses a 2D image data called GeoTiff, which represents elevation in shades of gray. Since the data will be divided into a mesh with pixel pitch, it is not possible to increase the resolution of only a portion of the data, and all areas will have a fixed-length mesh resolution.
To create terrain data for arcAstroVR from GeoTiff, use the free GIS software "QGIS". GIS is software for processing geographic information data, and GioTiff is one type of geographic information data. For the wide-area terrain, you can use the ALOS 30m mesh global data, which is available from JAXA for free of charge. You can use any elevation data (GeoTiff, etc.) other than JAXA's ALOS 30m mesh data that can be imported into QGIS to create terrain data for arcAstroVR.

*The resolution of arcAstroVR wide-area topographic data is fixed at 24.414m. The pixel size of the wide-area terrain is 4096 x 4096 px, so the area that can be represented is 100 km per side (=24.414 x 4096). arcAstroVR arranges 9 tiles of wide-area terrain data with 100 km per side to cover a total area of 300 km x 300 km. The total area is 300 km x 300 km. *We recommend using mesh data of about 20 to 30 meters for the original data of wide-area terrain.

Obtaining terrain data

The Japan Aerospace Exploration Agency (JAXA) releases free of charge (registration required) global numerical elevation data with 30-meter resolution from data acquired by the Advanced Land Observing Satellite "Daichi" (ALOS). In this section, we will use the 30-meter mesh data (GeoTiff) from JAXA ALOS as an example of terrain data.

After you register on the User Registration page (https://www.eorc.jaxa.jp/ALOS/aw3d30/registration_j.htm), you will receive an email with your password.
Once you have the password, go to the download page(https://www.eorc.jaxa.jp/ALOS/en/aw3d30/data/index.htm) and click on the area on the map that you want to download. The first time you do this, you will be asked to enter your ID and password.
You cannot download the entire globe at once. You must click on an area and enlarge it to a size that will allow you to download. Once the area is enlarged to the point where the Download button appears, click Download to download.
A zip file will be downloaded containing the latitude and longitude of the selected area in the file name (e.g. N033E130.zip). After unzipping, you will see a file named ALPSMLC30_(latitude/longitude)_DSM.tif. This file is the 30m resolution elevation data GeoTiff.
Follow the above procedure to download all terrain data for an area that includes a radius of 150 km from the observation point.
Open QGIS and drag and drop all downloaded GeoTiff files (ALPSMLC30_(latitude/longitude)_DSM.tif) into the Layer column to register them.
Select QGIS Menu > Raster > Miscellaneous > Merge
Click the ... button in the input layer column of the gdal_merge dialog that appears.
Check the registered GeoTiff layers and return to the parameter screen by clicking the ◀︎ button in the upper left corner.
Click the Output Layer column ... button and set the output destination and output file name.
Click the Run button, and when the calculation is finished, click the Close button to close the gdal_merge dialog box.
An integrated layer called 30mDEM is created in the Layer column. Select the individual layer before integration and delete it by Right click > Remove Layer....
This completes the registration of multiple GeoTiffs into QGIS and their integration into the layer 30mDEM.