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Lunchless Learn

Lunchless Learn. So you want to make a map: Where & how to find data. Agenda. Geospatial data – What is it? How is it made? Vector vs Raster File formats Projections Data Sources Q & A Session Evaluation. What if I have questions?.

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Lunchless Learn

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  1. Lunchless Learn So you want to make a map: Where & how to find data

  2. Agenda • Geospatial data – What is it? How is it made? • Vector vs Raster • File formats • Projections • Data Sources • Q & A • Session Evaluation

  3. What if I have questions? • Feel free to ask questions throughout the session – just raise your hand • There are no stupid questions (trust us!) • One voice at a time please!

  4. Geospatial Data What is it? place + attribute + time* • Locations and descriptions of geographic features; a combination of spatial data and descriptive data • Geospatial data can be linked to other ‘non-spatial’ datasets * time is optional

  5. Estimates are that 80% of all data has a spatial component!

  6. Geospatial Data How is it collected? • Survey Techniques • Aerial Photography & Remote Sensing • GPS • Geo-coding & Databases • Digitizing & Scanning

  7. Survey Techniques • Defining the location of a point in our environment • Location is relative • Determining new positions with respect to existing reference features • Measuring angles & distances from geodetic control points

  8. Aerial Photography • Topographic map compilation • Resource inventories • Large areas in great detail

  9. Remote Sensing • The science of deriving information about the earth from images acquired at a distance. • Methods: • aerial photography • radar • satellite imaging

  10. GPS Global Positioning System • Satellite-based navigation system • 24 orbiting satellites • Originally intended for military • Made available to all in 1980’s • Works in any weather, anywhere on earth, 24 hours a day

  11. GPS • Satellites circle earth twice a day (7000 miles/hour!) • Transmit info to earth • GPS receivers use info to calculate location • Extremely accurate

  12. Geo-coding & Databases • A method of attaching spatial locations to datasets • Often done with addresses • Can be used with any database containing a locational attribute

  13. Scanning & Digitizing • Creating vector data from images • Hard-copy maps, aerial photographs • Digitizing tablets, graphics packages • Scanning & georeferencing

  14. Types of GIS Data

  15. Vector Deals with features: Points, Lines, and Polygons (topographic data) Raster Uses pixels or arrays of cells to represent features on the earth (satellite imagery, air photos, scanned images) Types of GIS Data

  16. File Formats What is a File Format? • File format is the mechanism of how data is stored on the computer. It indicates to the system where to look for various pieces of information. • Format is important as not all GIS read all types of formats.

  17. File Formats What do they include? Geographic Information – Where data is located and its shape Attribute Information – Additional non-spatial data Display Information – How features will display on screen * Not all formats have all 3 types of info

  18. Vector Formats ESRI Formats • Shape files (.SHP) – A set of related files that have the same name but different extensions (.shp, .shx, and .dbf) • Coverage – A directory that contains a set of files. This is an older ESRI format • Geodatabase – A mechanism to put many layers or themes into a single file • Arc Export (interchange) format (.E00)– An exchange format that bundles coverage into a single file. Must be uncompressed / imported before it can be used

  19. Vector Formats Formats ESRI Accepts • Autodesk Data Interchange Format (.DXF) • MapInfo Data Transfer Files (.MIF) • Digital Line Graphs (.DLG) • S57 International Hydrographic Organisation Transfer Standard for Electronic Navigation Charts (.ENC) • Spatial Data Transfer System (SDTS) • Vector Product Format (.VPF)

  20. Vector Formats Vector Formats not supported by ESRI • AutoCAD Drawing File (.DWG) • MapInfo Files (.MAP) • Caris export format (.NTX)

  21. Raster Formats ESRI Internal Format • Grid • ASCII (.TXT, .ASC)

  22. Raster Formats Formats ESRI Accepts • Band Interleaved by Line (.BIL) • Tagged Image File Format / Geotif (.TIF) • USGS Digital Elevation Model (.DEM)

  23. Coordinate Systems & Projections

  24. Coordinate Systems • Also known as reference systems • Set of lines • Known locations used to determine feature locations 2 types: • Geographic • Projected

  25. Geographic Locate objects on a curved surface Projected Locate objects on a flat surface Coordinate Systems

  26. Geographic Coordinate Systems Longitude and latitude are angles measured from the earth’s centre to a point on the earth’s surface

  27. Projected Coordinate Systems Feature locations are measured using x and y coordinate values from the point of origin

  28. Geographic Network of intersecting lines called a graticule Latitude & longitude Measure of angle from earth’s centre to a point on the surface Measurements expressed in degrees, minutes, seconds Goal is locational accuracy Projected Uses a grid with an x and y axis Latitude & longitude converted (projected) to planar coordinates Locations are measured with an x and y value from a point of origin Goal is accurate analysis (measure distance, calculate area, shortest distance) Coordinate Systems

  29. Datums • The earth is not a perfect sphere – it’s a spheroid • Spheroids can be used to represent the earth • Many different spheroids With coordinate systems, datums specify which spheroid is being used to model the earth

  30. Coordinate Systems All geographic datasets have a geographic coordinate system Some datasets also have a projected coordinate system Your datasets may or may not have the same coordinate system http://projections.mgis.psu.edu/

  31. Coordinate Systems ArcMap has “on-the-fly projection” This method of projection works - as long as your datasets share the same geographic coordinate system If not, there may be some misalignment

  32. Show me the data!

  33. So where can I find data? • Dalhousie’s GIS Centre • Municipal, Provincial & Federal Government • Private Companies • Community Groups & Organizations

  34. Scale Issues Many data sources = data at many different scales This is common and poses a challenge for interpretation & analysis

  35. Data at the GIS Centre • HRM Topo Data, 1:1,000 • NS Topo Data, 1:10,000 • NS Forestry Data, 1:10,000 • National Topo Data, 1:50,000 & 1:250,000 • DMTI Spatial Data, variable scales • ESRI data, variable scales

  36. Data at the GIS Centre Browse our website: http://magic.library.dal.ca Then contact us! We will package the data and deliver it to you via e-mail, our FTP site or a jump drive

  37. Free Data??

  38. Other Data Sources There are a number of sources to access data: • Data Warehouses • Internet • Contacting Mapping Organisations • Collecting your own

  39. Useful (FREE) Online GIS Data Sources Topography – Roads, coastlines, cities etc… Nova Scotia - http://www.gov.ns.ca/snsmr/land/ New Brunswick - https://www.web11.snb.ca/snb7001/e/2000/2900e_1.asp GeoGratis – maps, satellite, tabular data http://www.geogratis.ca/ GISDataDepot – worldwide datasets, coarse resolution http://data.geocomm.com/catalog/index.html Geoconnections – contains links to GIS data and maps http://www.geoconnections.org/CGDI.cfm NGDC – Geophysical data, elevation and bathymetry http://www.ngdc.noaa.gov/ Agriculture Canada - soils database http://sis.agr.gc.ca/cansis/nsdb/detailed/intro.html

  40. Scenerio Planning on doing sampling exercise in the Bay of Fundy. Asked to create maps showing where data has already been collected. Would also like to have information on depths in the area. Data Requirements: • Sample Locations • Bathymetry data • Coastal Outlines

  41. Bringing ASCII data into ArcMap Step 1 – Get data • To bring data into ArcMap, data must be in either .dbf format (DBase) or .csv (comma separated/delimited). • Conversion to either of these formats can be done through Microsoft Excel * Recommend .csv as there is usually fewer formatting issues. • Go to: http://www.gsca.nrcan.gc.ca/ed/ *** This site is now Password Protected and you must contact organization Click Access ED button

  42. Accessing ASCII Data

  43. 1 2 Accessing ASCII Data

  44. Accessing ASCII Data

  45. Accessing ASCII Data

  46. Accessing ASCII Data

  47. Accessing ASCII Data C:\temp\LunchlessLearn

  48. Removing all Special Characters Step 2 - Verify Format in Text Editor • First row in data must be attribute names • Must be no special characters in the attribute name (only letters, numbers and underscores) X Spaces X Slash/backslash X Quotes • Attribute name must not begin with a number

  49. Removing all Special Characters • Open file just created in Wordpad • Remove parts not related to the data (HTML tags) • Remove spaces and slashes in attribute names • Save File with same name

  50. C:\temp\LunchlessLearn Removing all Special Characters

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