Remote Sensing and GIS
Core concepts
Remote sensing acquires information about the Earth without contact. Know the electromagnetic spectrum, atmospheric windows, and the difference between passive (reflected solar, emitted thermal) and active (radar, LiDAR) sensors. Understand spatial, spectral, temporal and radiometric resolution, and how they trade off. Study platforms: satellite orbits (geostationary, sun-synchronous polar), and sensors such as Landsat, Sentinel, SPOT, and MODIS. Learn image interpretation elements (tone, texture, pattern, shape, shadow, association), and vegetation indices like NDVI. GIS concepts include vector versus raster data, topology, attribute tables, coordinate systems and projection, overlay, buffer, and spatial interpolation. Bangladesh applications include flood mapping, cyclone damage assessment, crop area estimation and urban growth monitoring.
Traps
Do not confuse resolution types: high spatial resolution does not imply high spectral resolution. A common error is calling radar passive; it is active and cloud-penetrating. Another trap is mixing vector and raster operations (buffering is primarily vector; reclassification is raster). Remember that NDVI uses near-infrared and red bands, not thermal.
Worked example
You must map flood extent during monsoon cloud cover. Rule of thumb: choose sensor by constraint. Optical sensors are blocked by cloud, so use active microwave (SAR) such as Sentinel-1, comparing pre- and post-event backscatter; water surfaces appear dark due to specular reflection. Then overlay with settlement and crop layers in GIS to estimate affected area.
Environmental Geography and Disaster Management
Core concepts
Environmental geography links physical processes, human pressure and policy response. Know ecosystem concepts: food chains, trophic levels, energy flow, nutrient cycling, biodiversity hotspots, and ecological footprint. Study pollution types (air, water, soil, noise), greenhouse gases and the enhanced greenhouse effect, ozone depletion by CFCs, and acid rain chemistry. Understand climate-change impacts and instruments: UNFCCC, Kyoto Protocol, Paris Agreement, IPCC reports, and mitigation versus adaptation. Disaster management requires the disaster cycle (mitigation, preparedness, response, recovery) and hazard typology: geological (earthquake, landslide), hydrometeorological (cyclone, flood, drought), and biological. In Bangladesh, know cyclone early warning and shelters, flood forecasting, embankment debates, and the Standing Orders on Disaster. Also cover EIA, environmental laws, and sustainable development goals.
Traps
Distinguish mitigation (reducing emissions or hazard impact) from adaptation (adjusting to effects); questions often swap them. Do not confuse the greenhouse effect with ozone depletion, which involves stratospheric chlorine chemistry and ultraviolet radiation. Another trap is treating all floods as purely natural when embankment and drainage management matter.
Worked example
Classify a coastal embankment raising and a crop-variety switch to salt-tolerant rice. Rule of thumb: ask whether the action reduces the hazard or adjusts to it. Raising embankments is structural mitigation; switching to salt-tolerant varieties is adaptation. Both can coexist in a disaster risk reduction plan, and neither removes the underlying cyclone hazard.