Monday, October 5, 2015

Conversion of existing digital data

An important technique that is becoming increasingly popular for data input is the conversion of existing digital data. A variety of spatial data, including digital maps, are openly available from a wide range of government and private sources. The most common digital data to be used in a GIS is data from CAD systems. A number of data conversion programs exist, mostly from GIS software vendors, to transform data from CAD formats to a raster or topological GIS data format. Several adhoc standards for data exchange have been established in the market place. These are supplemented by a number of government distribution formats that have been developed. Due to the wide variety of data formats, most GIS vendors have developed and provide data exchange/conversion software to go from their format to those considered common in the market place.

Most GIS software vendors also provide an ASCII (American Standard Code for Information Interchange) data exchange format specific to their product, and a programming subroutine library that allows users to write their own data conversion routines to fulfil their own specific needs. As digital data becomes more readily available this capability becomes a necessity for any GIS. Data conversion from existing digital data is not a problem for most technical persons in the GIS field. However, for smaller GIS installations who have limited access to a GIS analyst this can be a major problem in getting a GIS operational. Government agencies are usually a good source for technical information on data conversion requirements.

Some of the data formats common to the GIS marketplace are listed below.

IGDS - Interactive Graphics Design Software (Intergraph / Microstation)

This binary format is a standard in the turnkey CAD market and has become a de facto standard in the mapping industry. It is a proprietary format, however most GIS software vendors provide DGN translators.

DLG - Digital Line Graph (US Geological Survey)

This ASCII format is used by the USGS as a distribution standard and consequently is well utilized in the United States. It is not extensively used even though most software vendors provide two way conversion to DLG.

DXF - Drawing Exchange Format (Autocad)

This ASCII format is used primarily to convert to/from the Autocad drawing format and is a standard in the engineering discipline. Most GIS software vendors provide a DXF translator.

GENERATE - ARC/INFO Graphic Exchange Format

A generic ASCII format for spatial data used by the ARC/INFO software to accommodate generic spatial data.

EXPORT - ARC/INFO Export Format .

An exchange format that includes both graphic and attribute data. This format is intended for transferring ARC/INFO data from one hardware platform, or site, to another. It is also often used for archiving.

ARC/INFO data. This is not a published data format, however some GIS and desktop mapping vendors provide translators. EXPORT format can come in either uncompressed, partially compressed, or fully compressed format

A wide variety of other vendor specific data formats exist within the mapping and GIS industry. In particular, most GIS software vendors have their own proprietary formats. However, almost all provide data conversion to/from the above formats. As well, most GIS software vendors will develop data conversion programs dependant on specific requests by customers. Potential purchasers of commercial GIS packages should determine and clearly identify their data conversion needs, prior to purchase, to the software vendor.