Post on 20-Jun-2015
From Geographic Information to GISGetting the Map into the computer
Part I: Data Collection
Arnaud Vandecasteele
Memorial Univ. of Newfoundland,
Canada
3/02/2013
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Outline
Introduction
1 - Data Collection
2 – Conversion process
3 – Data Storage
4 – Data Analysis
Conclusion
Introduction
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Objectives
Methods to acquire GIS data, particularly via the GPS
Methods to create new GIS data
Processes to edit existing GIS data
Types and sources of error potentially associated with GIS data
Introduction
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GeoSpatial Revolution
Introduction
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Fonseca et al., 2002
From physical reality to computer
How to represent reality ?
Introduction
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From physical reality to computer
REAL WORLD
VECTORGRID RASTER
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Source: http://www.uvm.edu/~gis/
Introduction
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Data Collection Process
.Gpx
ConversionProcess
DataCollection
DataStorage
DataAnalysis
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Geodata collecting
Two main types of data capture:
● Primary data sources (direct measurement) collected in digital format specifically
for use in GIS (e.g., GPX, Satellites Images)
● Secondary sources (indirect derivation) need to be converted into a suitable digital for use in a GIS project (e.g., CSV, Excel, etc.)
Data Collection Conversion Process Data Storage Data Analysis
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Raster Data Capture(Remote Sensing)
You are not directly measuringthe object, but is reflectance
Vector Data Capture
GPS, LiDAR
● Primary data sources (direct measurement) collected in digital format specifically
for use in GIS (e.g., GPX, Satellites Image)
Data Collection Conversion Process Data Storage Data Analysis
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<?xml version="1.0" encoding="UTF-8"?><gpx version="1.0">
<name>Example gpx</name><wpt lat="46.57638889" lon="8.89263889">
<ele>2372</ele><name>Example Points</name>
</wpt><trk><name>Example gpx</name><number>1</number><trkseg>
<trkpt lat="46.57608" lon="8.89241"><ele>2376</ele><time>2007-10-14T10:09:57Z</time></trkpt><trkpt lat="46.57619" lon="8.89252"><ele>2375</ele><time>2007-10-14T10:10:52Z</time></trkpt><trkpt lat="46.57641" lon="8.89266"><ele>2372</ele><time>2007-10-14T10:12:39Z</time></trkpt>
</trkseg></trk></gpx>
Example of a GPX file
Example of a track
Example ofA waypoint
● Primary data sources (direct measurement) collected in digital format specifically
for use in GIS (e.g., GPS, Satellites Image)
Geodata collecting - GPS
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What is GPS
The Global Positioning System (GPS) is a constellation of satellites that is used to calculate your position.
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How GPS works ?
Each satellite continuously broadcasts timing information
20130203-1045-3001
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Each satellite continuously broadcasts timing information
20130203-1045-3001
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A GPS receiver measures distance using the travel time of radio signals
220130203-1045-3148
How GPS works ?
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How GPS works ?
Each satellite continuously broadcasts timing information
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A GPS receiver measures distance using the travel time of radio signals
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We are somewhere on the circle where these two spheres intersect
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Data Collection Conversion Process Data Storage Data Analysis
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Trilateration (Triangulation)
How GPS works ?
Each satellite continuously broadcasts timing information
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A GPS receiver measures distance using the travel time of radio signals
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The receiver calculates the distance to each satellite and trilaterates its own position
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We are somewhere on the circle where these two spheres intersect
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Data Collection Conversion Process Data Storage Data Analysis
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Are GPS perfect ?
● Ionospheric effects ± 5 meters
● Tropospheric effects ± 0.5 meter
● Ephemeris errors ± 2.5 meters
● Satellite clock errors ± 2 meters
● Multipath distortion ± 1 meter
● Numerical errors ± 1 meter
Accuracy – sources of errors
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Geodata conversion
.Gpx
ConversionProcess
DataCollection
DataStorage
DataAnalysis
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<?xml version="1.0" encoding="UTF-8"?><gpx version="1.0">
<name>Example gpx</name><wpt lat="46.57638889" lon="8.89263889">
<ele>2372</ele><name>Example Points</name>
</wpt><trk><name>Example gpx</name><number>1</number><trkseg>
<trkpt lat="46.57608" lon="8.89241"><ele>2376</ele><time>2007-10-14T10:09:57Z</time></trkpt><trkpt lat="46.57619" lon="8.89252"><ele>2375</ele><time>2007-10-14T10:10:52Z</time></trkpt><trkpt lat="46.57641" lon="8.89266"><ele>2372</ele><time>2007-10-14T10:12:39Z</time></trkpt>
</trkseg></trk></gpx>
.Gpx
Geodata conversion process
Point Line (track)
Data Collection Conversion Process Data Storage Data Analysis
.Gis
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Geodata conversion process
GPSBabel @ http:/ /www.gpsbabel.org
Converts data between popular GPS Extensive data manipulation abilitiesMulti-platform (e.g., Windows, Mac, Linux)User Interface
Data Collection Conversion Process Data Storage Data Analysis
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Geodata Storage
.Gpx
ConversionProcess
DataCollection
DataStorage
DataAnalysis
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Proprietary SystemsOracle Spatial, Microsoft SQL Server
Open SourcePostgreSQL/Gis, MySQL, SQLite
Service BasedGoogle BigTable, Amazon SimpleDB
Geodata storing
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Geodata storing
PostGis @ http:/ /postgis.refract ions.net/
Project started in 2001Based on PostgresqlMany GeoFunctions (e.g., Buffer, Intersects)Geometric, Geographic and Raster data
MySql Spatial @ http:/ /dev.mysql.com/
Integrated into MySQL since 4.1Geometric data (plan)
No projectionFew spatial function
SpatialLite @ http://www.gaia-gis. it /spat ial i te/
Based on SQL LiteMinimal weight (250 ko)Many GeoFunctions (e.g., Buffer, Intersects)User Interface
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How GeoData are storing ?
<trk><name>Example gpx</name><number>1</number><trkseg><trkpt lat="46.57608" lon="8.89241"><ele>2376</ele><time>2007-10-14T10:09:57Z</time></trkpt><trkpt lat="46.57619" lon="8.89252"><ele>2375</ele><time>2007-10-14T10:10:52Z</time></trkpt><trkpt lat="46.57641" lon="8.89266"><ele>2372</ele><time>2007-10-14T10:12:39Z</time></trkpt>
</trkseg></trk>
GPX
ele time geom_wkt1 2007-10-
14T10:09:57ZLINESTRING(46.57608 8.89241,46.57619 8.89252,46.57641 8.89266)
ele time geom_wkb1 2007-10-
14T10:09:57Z010200002031BF0D000900000085EB5140E...1F6285CDFAED567C185EB5118DF664E41
WKTWell Know Text
WKBWell Know Binary
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.Gpx
ConversionProcess
DataCollection
DataStorage
DataAnalysis
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Geodata visualisation - desktop
Data Collection Conversion Process Data Storage Data Analysis
ArcGis@ http://www.esri.com
QGIS@ http://www.qgis.org/
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Geodata visualisation - internet
Data Collection Conversion Process Data Storage Data Analysis
ArcGis@ http://www.arcgis.com
OpenLayers@ http://www.openlayers.org/
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Quality insurance
Positional accuracyDefined as the closeness of locational information to the true position
Attribute accuracyDefined as the closeness of attribute values to their true value
Logical consistencyRefers to the internal consistency of the data structure,
particularly applies to topological consistency
CompletenessConcerns the degree to which the data exhausts the universe of possible items
LineageA record of the data sources and of the operations which created the database
Conclusion
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Looking for software?OSGEO-Live
http://live.osgeo.org/
OSGEO-Live
Conclusion
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Geographic Information Systems and SciencePaul A. Longley, Mike Goodchild, David J. Maguire, David W. Rhind2010
To go further
Conclusion
A primer of GISFundamental Geographic and cartographic concepts
Francis Harvey 2008
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Let's GeoPlay
Conclusion
Have Fun with Geography
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Geocaching
Can I Geo Play ?
Geocaching (http://www.geocaching.com/)
Outdoor recreational activity in which the participants use a GPS to hide and seek containers, called "geocaches" or "caches", anywhere in the world
Conclusion
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Conclusion
Geocaching
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Can I Geo Play ?
OpenStreetMap (http://www.openstreetmap.org/)
Outdoor recreational activity in which the participants create free geographic data for the world.
OpenStreetMap
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OpenStreetMap
OpenStreetMap @ http://www.openstreetmap.org/
Conclusion
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Have Fun with Geography
Activity 1 - Find the Geocache located at :Nad 83 → Lat 47°34.334, Lon -52°43.858
Activity 2 - Record OpenStreetMap GeoData
Thanks to the weather
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Equipment
GPS Mobile App Walking Paper