NASA World Wind: FAQs on Imagery
Following are some basic questions on NASA world wind imagery.
Why I am not able to see my car and house?
This is USGS (United States Geological survey) urban area imagery. USGS is approximately 0.25 m/pixel and covers only certain areas in United States. These are color images you might have seen. Generally, you can see cars and houses with this layer. However, it is available in select cities. The images will definitely be white if you are looking at the wrong place. Alternatively, you can also use USGS 1m/ topography that cover entire United States but is in white and black color. You will be able to see most roads and buildings.
Can I use it for non-US locations?
USGS has very high-resolution data that is available only for United States. However, 'Landsat' data is globally available. Landsat is a satellite that is capable of giving moderate resolution image data of Earth's surface. While high-resolution imagery is available for other places most of it is licensed. You can also go for virtual earth plug in which provides hi resolution data for countries like Italy, Japan, UK and Australia.
Will I be able to watch the world in real time?
This is not just practical and it will not be possible in the near the future. To achieve this requires a large network of satellites that is dedicated to cover the globe. The biggest problem is the internet connection as it is too slow to receive real time images.
Why do I see white tiles when I view USGS urban data?
Unfortunately USGS urban data is not available everywhere. If you are not looking in the correct place, you will see whitish green. The pictures also sometimes look blurry.
Is data in USGS layers available freely in countries other than United States?
Unfortunately, data in other parts of the globe is not freely available, that is why data is not incorporated into NASA World wind.
Can the images that are shown on World wind be used for commercial purposes?
Datasets that the software has access are in 'Public domain', hence you can use it for commercial purposes. However, there are some data sets have their own rules and conditions which can prevent commercial use of their services and products.
Why does relief feature such as mountain does not look, as it should?
There are many reasons behind it. If the area is flat then you are seeing an area that is below or above 60-degree latitude where elevation data is not there as the satellite that took the image and measurements orbited around the equator.
Another possibility may be that the elevation data is taken using sonar measurements (elevation sounded from a satellite). These soundings are unfortunately taken every 90 meters. That is why mountains and such other features may look very strange. In some cases, soundings were not obtainable in areas that have very high relief. Therefore, data derived from these areas will not be accurate.
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