processing landsat 8 multi-spectral images with grass tools & the potential of the...

Paul Shapley MSc CGeog (GIS) FRGS

http://www.paulshapley.comemail: p.shapley@gmail.com

QGIS User Group (Wales)6th October 2015

Processing Landsat 8 Multi-Spectral Images with GRASS Tools

& the potential of the 'QGIS-GRASS-PLUGIN'

So...who am I?

● Originally a Chartered Designer working in Design and Advertising until 1993. I now work as a GIS Supervisor and LLPG Custodian for Neath Port Talbot Borough Planning Department using QGIS and GRASS daily for the LLPG and LDP Team.

● Have been a QGIS user since about 2007 (I was looking for an ArcMap alternative on MacOS) then Windows and more recently Ubuntu.

● We are just completed our LDP mapping requirements almost entirely with QGIS for both print production and the web.

● I'm investigating the potential of Landsat 8 medium resolution imagery as a way of monitoring urban change, also want to investigate the use of 3D building access for the LLPG.

● Try to help and promote the Ubuntu GIS community by publishing a blog in my spare time.

Neath Port Talbot Local Development Plan

Landsat 8 – The Basics

● Launched February 11th 2013 – Circles the earth 14 times a day

● 8th Satellite in the Landsat Program which started in 1972

● The Mission: -

1) Collect and Archive Medium Resolution Images.

2) Ensure consistency with data from previous missions.

3) Distribute data products to the public.

● 15M, 30m and 100m Panchromatic, Multi-spectral and Thermal.

● 16 day cycle image taken at 11.15am (South Wales)

Possible Uses of Landsat 8 Data

● Landscape Assessment

● Environmental and Health Condition Monitoring

● Urban Change Detection

● Vegetation Greenness

● Landslide Detection and Susceptability

We are interested in the Visible, Near Infrared and Short Wave Infrared Bands

R = Red O = OrangeY = YellowG = GreenB = BlueV = Violet

Where 'ROYGBV' fits into the spectrum

What are the 11 bands of Landsat 8?

Multi-spectral band Reflectance %

Raw GeoTIFF Band 3 (Red)(v.in.ogr)

Panchromatic Band 8 after 'Histogram Equalise' (r.colors)

How do we get the raw data?

earthexplorer.usgs.gov PATH: 204 ROW: 24 Require: Level 1 GeoTIFF Data Product

Next we need to access the 'Landsat Archive' listing and tick 'L8 OLI/TIRS' then click on 'Results'.

For getting Bands into Grass 6. here is the link:

http://www.paulshapley.com/2014/04/processing-landsat-8-bands-in-grass-gis.html

Getting the Landsat 8 Bands into GRASS

Urban/IndustrialUrban/ResGreen VegetationShadowSea Water/CoastalSoil

Image Classification: 'v.gensigset' to capture a signature file which will be used to sample the underlying pixels into six groups.

'i.smap' will then create the necessary 'passes' to produce the suggested 6 areas (requires trial and error) to get precise groups

When the images are generated for each year of interest we can then animate the results similar to this '.gif'.

GRASS 7 (UBUNTU)Simple Two Box Application -

1) Toolbox/Feedback2) Map Window

Advantages of GRASS 7

1. One of the main advantages of GRASS over QGIS is the 'LOCATION' - A single data directory that is easily portable and ensures one or two years down the line you will not lose a layer connected with a project. For example you have to actively use the 'g.remove' command to ensure the layer is completely deleted and all it's constituant parts.

2. It has a simple, elegant, un-cluttered interface of just two windows - one for 'map', one for 'tools'

3. It is modular Based. All 400 or so modules can be accessed directly through the 'terminal' (not like microsoft word)

4. Run multiple modules simultaneously - only limited by processing and RAM of the hardware.

5. Good Vector Topology Checking/Reporting (Topology created on Input by default)

6. To repeat a Single Portable Directory Store (the 'LOCATION') for - Point, Centroid, Line, Boundary, Area, Face (3D Surface), 3D Centroid, Volume, 2D Raster, 3D Voxel (three dimensional cells), 'Multi-dimensional' Points

7. Good support for use with other Open Source Projects such as Paraview,Blender,Vis5D

8. Good DEM and Image Processing Tools and handling of large lidar datasets.

9. All Modules available through a WFS (Web Feature Service)

Disadvantages of GRASS 7

1. Steep Learning Curve 2. Vector Digitising not as 'slick' as QGIS3. Poor 'Layout' Editing Options (although improved in GRASS 74. 3D 'NVIZ' Module a little bit dated.5. No direct Web/HTML5 output options.

QGIS-GRASS-PLUGIN advantages

1. Direct access to the 'single data directory' (the 'LOCATION')

2. The QGIS API is more familiar than GRASS (just like microsoft word)

3. Drag 'n' Drop QGIS layers into the Grass 'PERMANENT' Mapset from within the QGIS Browser (no more lost shapefiles or forgotten usernames and passwords a year down the line.

4. 'Mapset' create/open/close directly in the Plugin

5. Attribute editing, digitizing and snapping will be using the more familiar QGIS toolbox.

6. If you just need the Grass Modules you can use the 'Processing' Toolbox if you dont need access to the Grass 'Location' and 'PERMANENT' mapset you need the Plugin.

7. 3D Visualisation using Google Earth

8. Direct migration of QGIS/GRASS data to QGIS-Server and others such as Geoserver/Mapserver etc.

QGIS-GRASS-PLUGIN UPDATE

● Last development was in 2004 for Grass V6

● Crowd Funded 'KiA' Model, goal was to raise 6,300 euros, 6,593 euros were raised.

● Completed Work on:

1) Browser Widget – drag and drop maps from Grass to QGIS view.

2) Update all to Grass 7

3) Attribute editing can be done in QGIS

4) Create forms for attribute capture in the plugin.

QGIS-GRASS-PLUGIN – Currently incomplete until QGIS 2.12

The Module 'Filter'Topic searching for Modules by simply typing: 'hy' (hydrology tools).

Main Toolbar – 'Under Plugins' if not showing.

QGIS-GRASS-PLUGIN for GRASS 6 here in QGIS 1.7 'Wroclaw'

'r.topidx' – Topographic Wetness Index Map - Wetness indices are used to describe spatial moisture patterns within a given region.

'r.hazard.flood' – Flood Prone Areas

'r.colors' to restrict color table from min = -34.98 max = 615.19 to 0.9 – 11.79m

5m Resolution DSM – limited colours to show heights -35m - 615m

'r.colors' – Just show heights between 500m and 615m

Steepness of Slopes 'r.slope' In Degrees of Inclination

'r.lake' consequences of sea level rise of about 3mm over 1000 year period.

Future Projects using Grass and the QGIS-GRASS-PLUGIN

● Integrate 3D data (e.g. building heights) as part of the LLPG Work flow to solve access points to multiple flats within a property shell. Property Shell Intelligence.

● Continue to Model Urban Change as part of the LDP Monitoring Process using Landsat8/Sentinel-2 images.

AnyQuestions?

Thank You all for NOT falling asleep…

Please contact me if you are thinking of using GRASS or QGIS-GRASS-PLUGIN and you would like some more

information:

p.shapley@gmail.com