April '19 Meetup Minutes

Covered Topics:

• Discover GIS Text Book
• Elevation & Bathymetry
• Semi-automated Classification Plugin (SCP)
• Adventures in Trail Mapping
• Share Recent QGIS Experience

The April meeting was held at Interim CDA. Thanks as always for their generous use of their conference room.

Just Raw Notes for Now

• Attendance was 100%. 6 out of 6 RSVPs attended. Perhaps a first
• Stu is moving to Mission Ridge, but will still be flying out of Kenmore
• Peter Keum bought the Discover QGIS 3.x by Locate Press
  • https://locatepress.com/dq3
  • Used for college classes
  • Has a section about changes from 2.x to 3.x
  • Doesn’t have a good index for reference purposes
  • About $25
• Clifford Snow got Learn QGIS: … 3.4 but hasn’t really looked at it.
• Peter Keum: Elevation and Bathymetry
  • Drawing hillshade on top of color ramp elevation/bathymetry
  • Properties, Symbology, Color Rendering, Blending Mode Multiply looks better than darken. Adjust contrast.
• Robert Catherman: Partial review and completion of using SCP for “Classification of Land Use”.
  • Volume 4 out of 5 in a series that is taught in Vietnam
  • Covers
    • Loading the plugin (SCP)
    • Downloading the Landsat images using SCP
      • SCP has a clip multiple rasters tool
    • Atmospheric correction of image
      • SCP can do it
      • USGS has level 2 images that are already corrected which the SCP author recommends if you can get it.
    • Define Regions of interest (ROI)
    • Classify areas of image
      • Pick areas as representative of classifications
      • Want to create classifications with very different values in the various spectral wave lengths (IR, Red, Green, Blue) for good classification
      • Can be told to be more fuzzy
    • Groundtruthing
      • Create random ROIs
      • Look at Google Earth to determine what the land is.
      • Performs an accuracy assessment
        • “Kappa hat” Kappa Coefficient or KHAT is the measure of accuracy - https://www.tandfonline.com/doi/abs/10.1080/02693799608902099
• Allie M - Trails Map
  • Having some trouble with the blend-mode and different projections
    • Important to leave the correct projection set for the layers.
  • We worked as a group on setting up using the blend-mode like Peter above
    • Tried hillshade or image on top.
    • Tried adjusting a lot of stuff.
    • Gave up on getting the blend tool from GRASS to work
  • Talked about Color Brewer
• Around the table, what have we been working on
  • Paul - Cluster centroids - Point Aggregation
  • Clifford - Accessibility data in 3 cities in NW Washington
    • Bellingham, Mt Vernon,
    • Calculating slope for roads and trails
    • AccessMap.io - you can see how it is working for sidewalks