Ways to capture GIS

Capturing GIS data consumes most available time for those that are practitioners of GIS. As such, there are a variety of methods used to enter data into a GIS where it is stored in a digital format. All existing data that has been printed on paper or PET film is able to be digitized or scanned to produce digital data. This would be a good time to define what a digitizer is and does.
A manual digitizer is a modified graphics tablet that uses a special magnetic pen, stylus, or puck that delivers information into a computer to create a digital map. These are rather expensive, however, they are very useful for GIS digitization  (http://www.digitizerzone.com/calcomp-db6.html):

Digitizers can produce vector data as operator trace points, lines, and polygonal boundaries from a map. A scanner is able to scan the results into raster data, which needs to be further processed to produce vector data:

Using survey instruments and a technique called coordinate geometry, the data can be directly entered into a GIS. GPS (global positioning systems) positions can also be collected and imported into GIS software. The current popular approach to data collection allows for field computers to edit live data via wireless connections or offline editing sessions.

The higher availability of lower-cost mapping-grade GIS with the ability of to-the-decimeter accuracy in real time enhances the ability to use field computers to edit the live data as well as positions collected by laser rangefinders. The advantage of using this technique is that it eliminates most of the postprocessing, importation, and updating of the data in the office after fieldwork.

More and more new technologies are being developed that allow users to create maps and conduct analysis in the field directly, which makes projects and mapping more efficient and accurate. Remote sensor data is an important if not critical role in data collection, which consists of sensors attached to a platform. These sensors include cameras, digital scanners, and lidar, and the platforms usually consist of aircraft and satellites.

In the mid 1990s, England created a kite and balloon hybrid called HeliKites. They pioneered the use of compact digital cameras as geoinformation systems for aerial GIS data collection. Aircraft measurement software is accurate to 0.4 mm and is able to link the photographs with the measurements to the ground. The advantage of using HeliKites is that they can be used over towns, railways, and roads, where UAVs (unmanned aerial vehicles) are banned from usage. Miniature UAVs such as drones have recently been used for aerial data collection. Most digital data is collected from aerial photographs currently.

There are soft copy workstations that are used to digitize features from stereo pairs of digital photographs. The stereo pairs of digital photographs allow for data to be captured in both two and three dimensions. Elevation is measured using principles of photogrammetry. If analog aerial photos are used, they must be scanned before they can be entered into a soft copy workstation, however, if a high-quality digital camera is used, then this step can be skipped.

Remote sensing from satellites is another important source used for spatial data. Satellites use different sensor packages to measure the reflectance from parts of the electromagnetic spectrum and/or radio waves. Remote sensing from satellites collects raster data that is further processed with different frequency bands; this allows for better identification of objects and areas of interest.

No matter the source of captured data, it is important to consider if the data is captured with relative or absolute accuracy. Choosing between relative or absolute accuracy influences how the information is interpreted and the direct cost to capture the data.

After the data has been entered into a GIS, the data usually requires editing. The editing ensures that errors can be removed or designates which portions of the data need to be further processed. Scanned maps may have blemishes on the source map that may need to be removed from the raster image. Vector data has to be made topologically correct before usage with advanced analysis.