Digital Orthoquadrangle and GeoTIFF

We have tested several GeoTIFF viewers that successfully display DOQ images and correctly ingest the geographic referencing information in the "geo tags." They are USGS's dlgv32, ArcExplorer on Win95, ArcView 3.0 (Unix), and ArcInfo 7.12 (Unix). According to information contained on the GeoTIFF page, there are several other systems with GeoTIFF ingest capability. They include MapInfo and IDL, and many more are either planned or functional.

The USGS is currently working on software to build the Spatial Data Transfer Standard (SDTS) "wrapper" or extension to the GeoTIFF DOQ. The SDTS "wrapper" will contain cartographic metadata such as data sources, dates, and quality. TIFF is an image format, and cannot easily accommodate these types of cartographic information. An SDTS/GeoTIFF DOQ transfer will consist of a number of files, most of which contain cartographic metadata (spatial reference descriptions, data sources, data quality) and one which contains the image. The image is the TIFF file, which includes georeferencing information conforming to GeoTIFF. The TIFF file does not require any preprocessing before you can read it with a TIFF viewer. This permits a non-SDTS application to still get to the image. It is important to note that the SDTS/GeoTIFF DOQ is not a separate or new distribution format, but rather it is the culmination of a single format being released in two phases. The DOQ in GeoTIFF (no SDTS) is being released immediately (Phase I) to give customers quick access to our DOQs. Shortly, we will enhance the GeoTIFF package by adding the SDTS wrapper (Phase II). Release of the GeoTIFF/SDTS DOQ is forthcoming.

Watch this site for information on SDTS translators. The USGS is developing programs that can be used as examples for reading SDTS metadata content.

Because you can directly read a DOQ into many programs that read TIFF images, you can use image rendering software to combine images, merge them to form a mosaic, and superimpose thematic data using the DOQ for geographic reference. The USGS uses DOQ images to revise maps, and you can also use your photo interpretation skills to "heads-up-digitize" features you can see on the image. Because it is geographically referenced, everything you digitize is similarly registered to a map and to the earth. Since most DOQ images are panchromatic (black and white), you may even try to extract color from lower resolution satellite images and then integrate the color with the spatial detail from the higher resolution DOQ. An example is near the bottom of this page.