Qatar's Digital Topographic Database is complete and comprehensive. Generally speaking it is a computerized, extremely accurate representation of all stationary features, both natural and man made that can be seen on Qatar's landscape.

All data in the Digital Topographic Database is structured in accordance with National GIS Database Specifications and Data Dictionary - Topographic Volume I. These data are on-line in a read only mode, around the clock, to all users linked by GISnet to The Centre for GIS.

The Digital Topographic Database is comprised of three separate components which have been designed and developed to meet all known GIS application needs of government.

The first component, the Digital Topographic Base Maps are up-to-date, digital vector maps which are used by a variety of government agencies as a base on which to superimpose their own thematic information. This in turn has simplified the subsequent correlation of any of these themes since they are positionally referenced to the same map base.

Having the base maps in digital form amplifies their utility as well as their versatility. Furthermore, as field crews are constantly providing data on new buildings, service extensions and other changes, the digital files are much easier to update than are paper maps.

All of Qatar's Digital Topographic Base Maps have been compiled using modern photogrammetric techniques. The urban areas have been stereo-digitized using 1:4,000 and 1:5,000 scale aerial photography typically used for the production of 1:1000 scale mapping.

Digital Topographic Base Maps for the entire country have been produced by stereo-digitizing 1:30,000 scale aerial photography which is typically used to produce 1:10,000 scale mapping.

The second component of the Digital Topographic Database is a high precision, Digital Elevation Model (DEM), which is comprised of a series of points on the earth's surface for which the elevation is known.

Topographic Vector Mapping - Downtown Doha

In the urban areas of Qatar, DEMs have been generated using 1:4,000 scale aerial photography. Each urban DEM comprises a mass of points spaced at intervals of approximately 8 metres on the ground, 90% of which are guaranteed to be vertically correct to within 10 cm. For the rest of the country the DEM has been generated from 1:30,000 scale aerial photography. The points in this country-wide DEM are spaced approximately 60 metres apart and are vertically accurate to within one metre.

Digital Elevation Model - Dukhan area

DEMs have seen a wide variety of uses in Qatar, including: the generation of contours; the compilation of Orthoimagery; the production of cross sections, the creation of three dimensional wire mesh drawings of the terrain, the computation of cut and fill volumes, and the design of roads and pipelines. They are particularly suited to preliminary planning of transmission lines and telecommunication networks where intervisibility between adjacent towers is critical.

The third component of Qatar's Digital Topographic Database is Orthoimagery. Digital orthoimages are scale corrected pictorial maps produced from aerial photographs which are rectified and reconstructed removing distortion created by terrain. The resultant image resembles an aerial photograph, but is a computer manipulated image in true map projection form.

Orthoimagery, comprised of 10cm pixels, has also been produced for all urban areas in Qatar using 1:4,000 scale aerial photography. Orthoimagey, comprised of one metre pixels, has been developed from 1:54,000 scale aerial photography, seamlessly joined together and enhanced in terms of contrast, to provide a continuous photographic dataset for the whole country.

All sensitive areas have been digitally obliterated to enable use of the data without imposing security risks.

Digital Orthoimagery - Downtown Doha

Because of its high resolution, the amount of detail it contains, and the fact it is on-line to all users, Orthoimagery has found a wide variety of applications in Qatar including: strategic planning; layout and design; inventory management and display; and as a backdrop for overlaying underground services and other thematic data.