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I downloaded a DEM from the Copernicus site.

I can provide the link: https://land.copernicus.eu/imagery-in-situ/eu-dem/eu-dem-v1-0-and-derived-products/eu-dem-v1.0?tab=download

I would like to find the date of my DEM, so as to compute sun elevation and azimuth..

Do you have any suggestions on how to do that?

I tried to find a metadata file.
I was trying to find out an xml file or a text file, but when i found it, it doesn't include the specific information.

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  • Can you provide us a bit more information? Which image did you download? Is there a link we can look at? Generally these types of data contain a metadata file (usually a XML or text file) that should have more details about the image, or sometimes the date and times are included in the name of the file. Nov 4, 2019 at 21:31
  • Yes, of course, I can provide the link: land.copernicus.eu/imagery-in-situ/eu-dem/… I was trying to find out an xml file or a text file, but when i found it, it doesn't include the specific information.
    – StavGian
    Nov 4, 2019 at 22:07

2 Answers 2

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Looking over the link, the data you are accessing is a culmination of various data sources to create a seamless grid of elevation data.

The "metadata" for the dataset:

https://land.copernicus.eu/imagery-in-situ/eu-dem/eu-dem-v1-0-and-derived-products/eu-dem-v1.0?tab=metadata

states:

The EU-DEM v1.0 is derived from an automated data fusion process using SRTM and ASTER GDEM digital surface model (DSM) data. Intermap's NEXTMap Europe dataset is utilized to remove any consistent horizontal bias in the GDEM data. The EU-DEM v1.0 is edited to ensure that water features are adequately represented and consistent with the hydrography layer. Residual clouds within the GDEM data are identified and removed same as suspect data extremely differing from the SRTM data.

There are a few lines that explain that this dataset is derived from both SRTM and ASTER datasets with some intervention to fix clouds, water features and horizontal bias.

Even though the data was published in April 2016, the metadata states that the datasets used are from around the year 2000...so would be a mix of images acquired over that year.

Therefore to answer your question, I don't think it is possible to extract a date and time for a given area.

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  • Thank you very much for your quick response..I think too that I won't find the specific data...
    – StavGian
    Nov 6, 2019 at 19:16
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A digital elevation model is not representing an optical property of the earth's surface, such as its reflectivity at certain wavelengths, nor is it influenced by the phenomena of refraction or diffusion that occur in the atmosphere.

Instead, it represents the elevation of the topographic surface with respect to a reference surface.

Although the model can be considered to represent these elevations at a given time, it is generally not a kind of instantaneous shot but rather the result of several measurements, even by different methods, at different dates and at different times.

Therefore, as reported by the site that provides the information, the information provided may be considered valid during the course of the year 2000.

Now, it is usual, that for illustrative purposes, we represent the shadows that this elevation model would produce on the surface at a particular time. We call the result of that representation: "hillshade".

If what you need is the apparent position of the sun in the celestial sphere, for a day, at a time and for a particular earth position, there are ways to find out. If you only want to make a shading for illustrative purposes, you could experience the parameters that make your representation produce the meaning you are looking to communicate.

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  • Thank you very much for your quick response! I wanted the apparent position of the sun in the celestial sphere, for a day, at a time and for a particular earth position, and specifically for that DEM, but it seems I won't find it! Anyway, thank you very much for your help!
    – StavGian
    Nov 6, 2019 at 19:18
  • You are welcome!. I'm curious as to why you would like that information for that DEM. Nov 6, 2019 at 22:55
  • I want to use a specific tool, the topographic modeling in ENVI, and for this procedure, I need to know sun elevation and azimuth of the DEM...
    – StavGian
    Nov 9, 2019 at 12:41

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