chapter 10. ï‚ data collection workflow ï‚ primary geographic data...
Post on 19-Jan-2016
Embed Size (px)
Data collection workflowPrimary geographic data captureSecondary geographic data captureObtaining data from external sourcesCapturing attribute dataManaging a data capture project
Primary geographic data sources are captured specifically for use in GIS by direct measurement. Secondary sources are those reused from earlier studies.Data capture costs can account for up to 85% of the cost of a GIS. Remote sensing is the measurement of physical, chemical and biological properties of objects without direct contact. three key aspects of resolution are: spatial, spectral and temporal.
Ground surveying uses measurement to determine the locations of objects.The GPS is a network of satellites, monitoring stations and inexpensive receivers used for primary GIS data capture.
Scanned maps and documents are used extensively in GIS as background maps and data stores. Manual digitizing is still the simplest, easiest and cheapest method of capturing vector data from existing maps.Vectorization is the process of converting raster data into vector data. The reverse is called rasterization.
Photogrammetry is used to capture measurement from photographs and other image sources.COGO stands for coordinate geometry. It is a vector data structure and method of data entry. The best way to find geographic data is to search the internet using one of the specialist geographic search engines such as the US NSDI Clearinghouse or the Geography Network. One of the good things about data standards is that there are many to choose from.
Data can be transferred between systems by direct read into memory or via an intermediate into file format.The most efficient way to translate data between systems is via a common intermediate file format. GIS data capture projects can be carried out intensively or over a longer period.