Simulic
English

GIS layers and remote sensing – overlay, buffers, NDVI and change detection

GeographyMaps & MappingAges 15–16

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A fictional 12 km × 8 km river valley with synthetic data: switch on and overlay layers for an aerial image, relief and contours, land use, flood zone, population density, income and roads, and tap any point to query every layer. GIS analysis counts homes in the flood zone, draws buffers around the river, roads or the clinic and finds the best site for a new clinic from several criteria. Remote sensing shows true and false colour, NDVI, a land-cover classification and the change between two dates ten years apart.

Lesson: Using maps and geospatial technologies: GIS layers, overlay and buffer analysis, satellite remote sensing

What it shows

A geographic information system (GIS) stores each theme – elevation, land use, roads, flood zones, census data – as a separate layer over the same area, so the layers can be overlaid and queried together. Buffers mark everything within a set distance of a feature, and overlaying conditions picks out suitable sites. Satellites record reflected light in several bands; healthy plants absorb red light and reflect near infrared, so false-colour images and NDVI = (NIR − Red)/(NIR + Red) map vegetation and its change over time. All data here are synthetic.

How to use

On Map layers, tick layers to overlay them and tap the map to query a point; switch Date between A and B. On GIS analysis, choose Homes in the flood zone, Buffer (pick Buffer around and Buffer distance) or Site a new clinic (set the distance criteria, then tap to test your own site). On Remote sensing, choose an Image type and tap pixels to read Red, NIR and NDVI.

Parameters you can change

  • Screen Map layers, GIS analysis, Remote sensing
  • Date Year 1 (A), 10 years later (B)
  • Aerial image layer
  • Relief and contours layer
  • Land use layer
  • Flood zone layer
  • Population density layer
  • Median income layer
  • Roads layer
  • Clinic and schools layer
  • Analysis Homes in the flood zone (overlay), Buffer, Site a new clinic
  • Buffer around River, Roads, Existing clinic
  • Buffer distance 100–2000 m
  • New clinic: maximum distance to a road 100–1000 m
  • New clinic: minimum distance from the existing clinic 0.5–5 km
  • Remote sensing image True colour (red, green, blue), False colour (near infrared, red, green), NDVI vegetation index, Land cover classified from NDVI, Change from A to B

Questions to explore

  1. Why do more homes lie in the flood zone at date B than at date A?
  2. Why does vegetation look red in a false-colour image?
  3. Which criteria limit the possible sites for a new clinic the most?

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