Remote sensing and change detection

Spectral band combinations, NDVI and riparian encroachment mapping from Landsat and aerial imagery

Academic coursework  /  2021-2022

Discipline
Remote sensing
Tools
ArcGIS
Methods
spectral band combination, NDVI, image classification, change detection, riparian buffer delineation
Data
U.S. Geological Survey; Manitoba Beef and Forage Initiative; Assiniboine Community College

Notes on method

A multispectral scene contains more than a person can look at, so the first decision is which three bands to put in the three colour channels. The comparison plate makes that decision visible: vegetation separates cleanly in one combination, built surfaces in another, bare soil in a third, and none of them is the right answer in general.

NDVI is the compression of that question into one number per pixel, which makes it comparable across dates and is why change detection uses it.

The riparian work is where the imagery becomes a decision. A protection zone drawn at 1:5,000 is something a producer can act on; the same zone at a provincial scale is a policy statement. Mapping encroachment on protected land means being willing to show where a boundary has been crossed, which is a different task from mapping where the boundary is.

Side-by-side Landsat 8 renderings of Portage la Prairie in different band combinations, where vegetation, built features and bare earth each separate most cleanly under a different combination.
The same scene under different band combinations. No single combination is correct; each one makes a different class separable.Base data: ACC. Scale 1:125,000Open larger (1669px)
NDVI surface over Portage la Prairie distinguishing vigorous vegetation from bare and built ground.
NDVI over the same area, reducing the band question to a single index.Base data: U.S. Geological Survey. Scale 1:150,000Open larger (2432px)
Riparian protection zones mapped along a watercourse on farmland north of Forrest, Manitoba, at 1 to 5,000 over aerial imagery.
Riparian protection zones north of Forrest at 1:5,000, where the buffer has to be drawn tightly enough to be actionable on the ground.Base data: Manitoba Beef and Forage InitiativeOpen larger (2432px)
Land and urban features classified around Riding Mountain National Park and Onanole, showing the boundary between protected land and settlement.
Land and urban features at the park edge near Onanole, where the protected boundary and the developed boundary do not coincide.Scale 1:75,000Open larger (2432px)