Data Input and data sources

1
Data Input and data sources

• Keyboard
• COGO
• GPS
• Scanning
• Digitizing
• Image processing (satellite images)
• File import -gt of data created by 1-6
• -------------------------------------------------
• File formats
• Small scale global data
• Medium scale national data
• Large scale provincial data
• Other data

2
1. Keyboard

•  .. primarily for attribute data

Spatial coordinates are mostly collected by the
other methods below
3
2. Co-ordinate geometry (COGO) 

• used for high precision municipal data, based on
  azimuth / distance from known points, rather than
  a coordinate system .. not common in natural
  resources.

4
3. Global Positioning Systems (GPS)

• A growing source of data since the early 1990s
  mostly spatial data e.g. new features such as
  trails, or cutblocks. Attributes can be added
  during data collection via a data table, or added
  in the Lab.
• See Geog205 lecture notes for more details on
  GPS. Smoothing of lines is done using GIS
  software.

5
4. Scanning

• Scanning produces a raster file that is used as a
  background layer for digitising (maps, photos)
• if 'clean, vectors can be extracted by
  automated 'line following'
• See for example http//www.scanners4cad.com/news_
  views/news_raster_to_vector_suitable.htm
• Scanning characteristics
• Electronic detector moves across image.
• Flat-bed (up to 11" by 17") and drum (full
  sheet).
• Creates raster data e.g. .tif format files
• generates large storage - possibly for few
  features ?
• Cannot easily recognize lettering, point symbol
  design,
• without sophisticated raster to
  vector (R2V) software

6
5. Digitizing

• Digitizing is done in two ways
• a. Following lines on maps using either a tablet
  with map taped down, or onscreen scan both are
  'second hand data' .. although the data on the
  map were created first hand by photogrammetry and
  photo interpretation
• b. Onscreen interpreted from digital (stereo)
  photogrammetry  ('first hand data')  
• Considered tedious but may be unavoidable to
  create usable vector layers

7
6. Digital Image processing (see GEOG432)
automated vectors from digital satellite imagery
8
7. Data file import

• This is the most common process today due to the
  supply of digital data- most have been created
  by
• i. digitizing existing maps or
• ii. interpretation of digital aerial photography
• The data are stored usually in standard formats
  formerly software could not read other formats
• A Vancouver company SAFE made it much easier with
  their product Feature Manipulation Engine (FME)
• 2009 supported formats http//www.safe.com/produ
  cts/desktop/formats/index.php

9
GIS file formats
Shapefiles (ESRI) Arcview .shp Spatial data
e.g. roads.shp .shx Link file
e.g. roads.shx .dbf Attribute data
e.g. roads.dbf .prj Projection
file http//en.wikipedia.org/wiki/Shapefile
10
Other GIS / mapping formats
Coverage (ESRI) - Arc/Info Layer name folder
e.g. roads (spatial) 6-10 files Info
folder
(attributes) many files Multiple files per
layer zipped into one export .e00
format Computer assisted drafting formats .dxf
(Autocad) .dgn
(Microstation) Raster formats .tif GeoTIFF
.grd (Arc/Info) multiple files
.jpg .bmp .gif ( others) graphics, no
georeferencing