More GeoProcessing Matthew Rosencrans Tom DiLiberto

Outline What else can we do in QGIS? Geoprocessing – Within the GUI

Geoprocessing Operations that can be done on and to GIS data – Analysis methods that are possible because of the geospatial nature of the data – Raster/Vector Bulk Statistics Zonal Statistics – Vector Intersections Dissolves, Clips, Buffers Joins (Spatial, non-Spatial)

Zonal Statistics – Statistics of a raster over each zone in a vector How much rain fell in each province? Gridded precipitation + Maps Provinces Zonal Statistics RedNW BlueSW YellowCenter GreenSouthCentral PurpleNE Light BlueSE

Zonal Statistics RedNW2.83 BlueSW3.9 YellowCenter3.93 GreenSouthCentral7.5 PurpleNE4.22 Light BlueSE6.53 Mean - get the Mean of the values, appended to the attributes of the polygons. Other functions available as well

Geoprocessing Intersections – Deal with areas where spatial data overlap Roads intersect with Counties Forecasts intersect with counties/provinces – Can help with impacted facilities, populations Spatial Join – Joins attributes, based on colocation

Intersections Determines the spatial reference. Also the spatial reference of the output feature class. Input features are projected into this spatial reference. Cracks and clusters. Cracking inserts vertices at the intersection of feature edges; clustering snaps together vertices that are within the xy tolerance. Discovers geometric relationships (intersections) between features from all the feature classes or layers. Writes these intersections as features (point, line, or polygon) to the output. Attributes from both input data sources are mapped to the retained features

Intersections Menu Bar Vector Geoprocessing Tools Intersect

Dissolve, Clip, Merge, Buffer Dissolves Merges 20km Clip

Joins (Spatial and Data) A common GIS task is to join the attributes from one spatial data layer to another. A spatial join involves matching rows in the attribute table from the join layer to the target layer based on a spatial relationship and writing to an output feature class. Like a join based on Data, but based on the location. NameNumber Tom123 Matt456 Wassila789 Joe321 Dave654 GradeNumber A123 B789 B321 C654 D456 NameNumberGrade Tom123A Matt456D Wassila789B Joe321B Dave654C

Joins (Spatial and Data) GIS data has an inherent spatial attribute, so it can join on that. Coincident points, lines, or polygons inherent the attributes from things that are spatially coincident. PointValue PolygonHazard 1TSTM PointValueHazard 10.9NULL 21.5TSTM 30.5TSTM 41.5TSTM 51.1NULL

Coding for Geoprocessing QGIS – Wasn’t able to get QGIS to work. ArcGIS is more familiar to me, and has scripting. – Will demo with that.

Aftenoon FINAL\NatEarth\10m_cultural\10m_cultural Load file for countries – ne_10m_admin_0_countries.shp Load file for states and citie – ne_10m_admin_1_states_provinces_shp.shp – ne_10m_populated_places_simple.shp forecast shapefiles that you made Monday – File has extremes, start, end – Perform intersection, spatial join

Country Climate Outlook Load shapefile of country – Extract your own country if you wish Load shapefile of states Create a new shapefile to contain your climate outlook Draw a climate outlook – Above Average Precipitation – Below Average Precipitation – Above Average Temperatures – Below Average Temperatures