Radiation Physics

• GPS Satellite Signal Transmission:
• GPS constellation satellites transmit low-power pseudo-random radio carrier signals.
• The primary civilian and military carriers are $L_1$ ($1575.42\text{ MHz}$) and $L_2$ ($1227.60\text{ MHz}$) in the UHF band.
• Conclusion: Statements (A) and (D) only are correct. (Correct answer: Option 2)

• Raster vs. Vector Data Models in GIS:
• Raster Formats: Continuous regular grid arrays of cells/pixels. Digital Elevation Models (DEM, C) and Digital Terrain Models (DTM, A) are classic continuous raster grids.
• Vector Formats: Feature models composed of coordinate points, lines, and polygons (e.g., Spaghetti models and Arc-node topological models).
• Conclusion: DTM and DEM (A and C only) represent raster data. (Correct answer: Option 4)

• Assertion (A) is True: In Geographic Information Systems (GIS), a map layer is an individual thematic spatial dataset representing a single attribute or geographic characteristic (e.g., elevation, soil type, vegetation) over a defined geographic domain.
• Reason (R) is True: The fundamental principle of topological GIS layering is that each individual thematic layer stores only one specific thematic attribute or information category per spatial location.
• Relationship: Because GIS layers are structured so that each layer represents a singular information class per coordinate, Reason (R) directly explains Assertion (A).
• Conclusion: Both (A) and (R) are true and (R) is the correct explanation of (A) (Option 1).

Correct option: (1) Both (A) and (R) are true and (R) is the correct explanation of (A)

• Vectorization Complexity:
• Converting raster pixel images into vector layers requires extracting geometric primitives (nodes, vertices, edges) and establishing explicit topological spatial relationships (adjacency, connectivity, containment).
• Because vector formats require topological structure building, automated vectorization is far more algorithmically complex than rasterization. (Correct answer: Option 1)