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GIS data files - PowerPoint PPT Presentation

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GIS data files

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    Slide 1:GIS data files

    GIS data layers are available from a variety of sources, generated mostly by digitizing of maps, or onscreen from photography. (Scanned maps are only useful as backdrop for digitizing) Special themes you just need to know who to contact General topographic data varies by country and province / region Scales of data In general smaller scale data are freely downloadable Medium-large scale costs money or needs arrangement Local (e.g. city) only by special arrangement Should all data collected at taxpayers expense be free ? There has been a general move towards making data available, especially this millennium

    Slide 2:GIS data: Global (small scale)

    The largest mapped scale for the whole world covered is 1:1,000,000. Created by digitizing the International Map of the World (IMW) The Digital Chart of the World (DCW) was completed in 1992 Free download, but is not suitable for larger scale mapping. IMW example:

    Slide 3:Federal: National Topographic DataBase [created by digitizing National Topographic Series maps]

    Topographic map data are available in digital form: 1:250,000: all of Canada 1:50,000 : all the provinces, parts of the Territories Since 2007, download data: NTS grid by province: National Atlas of Canada:

    One 1:250,000 map sheet contains 100 x 1:20,000 Each 1:250 000 is 1 degree latitude by 2 degrees longitude. Each 1:20 000 TRIM sheet is 6 latitude by 12 longitude. Total # map tiles = 7027 The province was digitally mapped at 1:20,000 from aerial photos taken in 1980s; completed 1996 Provincial (BC) GIS data

    Slide 5:BC 'TRIM' digital mapping (Terrain Resource Inventory Management)

    TRIM I data consisted of five sets of layers: a. Contours (lines for cartographic depiction). b. DEM (for 'analysis and hill-shading). c. Planimetric (points and lines, e.g. roads, rivers, buildings, etc). d. Text - annotation e. Control points (for photo correction) These form the basis for GIS in BC, the best provincial data but: a. The data are planimetrically correct but with few attributes b. There was limited ground checking c. By completion (1996), data were 7-15 years old .. Also at first tricky for many users to import before FME

    Slide 6:TRIM raster image from (scan)

    Slide 7:TRIM II 1997- ?

    Need for updating More detail photos 1:40,000 v 1:70,000 for TRIM I Add orthophoto layer Specs and more details: About 70% complete Progress:

    Slide 8:TRIM II coverage, showing areas with orthophotos (from imap)

    Slide 9:BC: Land and Resource Data Warehouse

    Download data from topographic + others Vegetation Resource Inventory by 1:20,000 tiles BEC zones Other parts of Canada: NWT: Yukon: Manitoba: PEI: 1:20,000 data: BC, AB, MB, Maritimes, southern ON/QC 1:50,000 (NTDB) for the rest SK, NL, northern ON/QC

    Slide 10:Some other types of data

    Municipal areas: data can be viewed but not usually downloaded e.g. pgmap Other data and map links Canada thematic (census) data: Thematic data are acquired from Statistics Canada. Universities take advantage of the 2001 Data Liberation Initiative These data are available through the UNBC spatial data librarian. Satellite (raster) imagery can be downloaded from many sites .. e.g. see GEOG432 Data download websites e.g.

    Slide 11:Assembling data

    View BC data at and - imap Data appears as a multiscale Seamless dataset Downloaded data are by map tile / sheet Desired area will need multiple (parts of) sheets Steps after download: Merge Dissolve Clip

    Slide 12:merge

    Slide 13:dissolve

    Slide 14:clip

    Software enables a batch clip for all designated layers

    Slide 15:Clipping for lines and points