The DSM is not an image, this is why it can not be opened by image viewers software, like the one of Windows. It should be opened by a GIS software that can understand that each pixel has altitude information.

Recommended software to open a DSM GeoTIFF:

• Global Mapper: It is a commercial software that has a limited free version. This limited version permits to open the DSM (drag and drop it).
• Quantum GIS (free software): Applications with Quantum GIS (QGIS).

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