Gdem30 data downloaded from geospatial data cloud is in img format after decompression, which can be viewed by global mapper software and converted into DEM, bt and other formats. As for how to use it, it depends on what you use it for. Generally, it is used to build a three-dimensional geospatial space, and you have to download high-resolution image data. Basically, high-resolution images are downloaded by paid software. When I did my graduation thesis, I bought the download device of Shuijing Note Google Maps, which cost 200 yuan.