18.11.2.1. Raster data

• Raster data: GeoTIFF, JPEG2000

Raster data is a type of digital image represented in a grid format. This means that the image is made up of individual cells (or pixels), where each cell contains information about the color and brightness. Two common formats for raster data are GeoTIFF and JPEG2000. GeoTIFF is a format that includes geographic metadata, allowing the data to be easily integrated with mapping systems, while JPEG2000 is known for its efficient compression and high quality.

Think of raster data like a mosaic made of small colored tiles. Each tile represents a pixel in the image, with its own color. Just as each tile fits together to form a beautiful picture, raster data is created by weaving together many pixels. GeoTIFFs are like mosaics with a label that tells you where they fit into the larger map, while JPEG2000 is like a beautiful photo that has been carefully compressed without losing its charm.

• Vector data: SHP, KML, GeoJSON

Vector data is different from raster data because it represents images using points, lines, and polygons instead of pixels. Each shape is defined by mathematical equations and coordinates, making vector data scalable without losing quality. Common formats for vector data include SHP (Shapefile), KML (Keyhole Markup Language), and GeoJSON. SHP files are widely used in GIS applications, KML is often used for displaying geographic data in web mapping applications like Google Earth, and GeoJSON is a format that makes it easy to share data across web platforms.

Imagine vector data as a blueprint for a house. The blueprint contains exact measurements and shapes of rooms, windows, and doors, which can be scaled up or down without losing any details. SHP files are like detailed blueprints used by architects, KML is like a blueprint shared with city planning on an online platform, and GeoJSON is like a blueprint formatted for easy sharing via email or websites.

• 3D data: LAS/LAZ (LiDAR), OBJ, STL

3D data formats store information about three-dimensional objects and environments. LAS and LAZ are file formats used specifically for LiDAR data, which captures detailed surface information using laser pulses. OBJ and STL are formats often used in 3D modeling and printing. OBJ files can contain complex geometries, while STL files are typically used for 3D printing due to their simplicity in representing 3D shapes.

Think of 3D data as the 3D models used in movies or video games. LAS/LAZ files are like the detailed models showing every little bump and texture of a mountain, while OBJ files are like well-crafted characters designed for movies. STL files are similar to the simpler 3D shapes created for 3D printing, where all that matters is the form without extra detail needed for visual effects.

• DEM/DTM formats: ASC, IMG, GRID

DEM (Digital Elevation Model) and DTM (Digital Terrain Model) are used to represent the elevation of the Earth's surface. DEM includes elevations that can represent natural features and built structures, while DTM specifically shows the bare Earth without any vegetation or structures. Formats like ASC (ASCII Grid), IMG (interchangeable image format), and GRID are common for storing this topographical data.

Consider DEMs and DTMs like topographical maps showing mountains and valleys. ASC files can be thought of as basic sketches drawn in pencil, where details are defined in plain text. IMG files are like detailed paintings that can capture more color and texture in the elevation, while GRID files are akin to graph paper where every square detail is clearly mapped out for accurate representation.

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