Data capture Geographic information system

example of hardware mapping (gps , laser rangefinder) , data collection (rugged computer). current trend geographical information system (gis) accurate mapping , data analysis completed while in field. depicted hardware (field-map technology) used forest inventories, monitoring , mapping.

data capture—entering information system—consumes of time of gis practitioners. there variety of methods used enter data gis stored in digital format.

existing data printed on paper or pet film maps can digitized or scanned produce digital data. digitizer produces vector data operator traces points, lines, , polygon boundaries map. scanning map results in raster data further processed produce vector data.

survey data can directly entered gis digital data collection systems on survey instruments using technique called coordinate geometry (cogo). positions global navigation satellite system (gnss) global positioning system can collected , imported gis. current trend in data collection gives users ability utilize field computers ability edit live data using wireless connections or disconnected editing sessions. has been enhanced availability of low-cost mapping-grade gps units decimeter accuracy in real time. eliminates need post process, import, , update data in office after fieldwork has been collected. includes ability incorporate positions collected using laser rangefinder. new technologies allow users create maps analysis directly in field, making projects more efficient , mapping more accurate.

remotely sensed data plays important role in data collection , consist of sensors attached platform. sensors include cameras, digital scanners , lidar, while platforms consist of aircraft , satellites. in england in mid 1990s, hybrid kite/balloons called helikites first pioneered use of compact airborne digital cameras airborne geo-information systems. aircraft measurement software, accurate 0.4 mm used link photographs , measure ground. helikites inexpensive , gather more accurate data aircraft. helikites can used on roads, railways , towns unmanned aerial vehicles (uavs) banned.

recently aerial data collection becoming possible miniature uavs. example, aeryon scout used map 50-acre area ground sample distance of 1 inch (2.54 cm) in 12 minutes.

the majority of digital data comes photo interpretation of aerial photographs. soft-copy workstations used digitize features directly stereo pairs of digital photographs. these systems allow data captured in 2 , 3 dimensions, elevations measured directly stereo pair using principles of photogrammetry. analog aerial photos must scanned before being entered soft-copy system, high-quality digital cameras step skipped.

satellite remote sensing provides important source of spatial data. here satellites use different sensor packages passively measure reflectance parts of electromagnetic spectrum or radio waves sent out active sensor such radar. remote sensing collects raster data can further processed using different bands identify objects , classes of interest, such land cover.

when data captured, user should consider if data should captured either relative accuracy or absolute accuracy, since not influence how information interpreted cost of data capture.

after entering data gis, data requires editing, remove errors, or further processing. vector data must made topologically correct before can used advanced analysis. example, in road network, lines must connect nodes @ intersection. errors such undershoots , overshoots must removed. scanned maps, blemishes on source map may need removed resulting raster. example, fleck of dirt might connect 2 lines should not connected.