Understanding Commonly Used GIS Data Types

GIS data types are divided into two main categories: vector and raster data. Each data type has its unique geographical characteristics, as well as its own advantages and disadvantages, which make it suitable for specific real world applications for GIS in construction.

Understanding Vector GIS Data

Vector data is a type of GIS data that represents attributes on the earth’s surface as points, lines, and polygons. It is commonly used to map discrete features such as roads, buildings, and water bodies. Vector data is stored as a series of x, y coordinates that define the shape and location of each feature. The three main types of vector data are point, line, and polygon features.

Point features refer to individual locations such as a city, a hospital, or a specific GPS coordinate. There is zero dimension to this data type, so it is not used to manage length or area.

Line features represent linear features such as roads, rivers, and pipelines. Since line data has only one dimension, it is only used to measure length.

Lastly, polygon features represent areas such as land parcels, parks, and lakes. These geometry-based features are two dimensional and are often used to signify perimeters.

The advantages of vector data are its ability to represent complex shapes and the ability to overlay data sets. However, the disadvantage is that it is not suitable for analyzing continuous data, such as elevation or temperature.

Vector data can be obtained from various sources, including:

1. Government agencies: Many governments provide free access to vector data on their websites. For example, the US Census Bureau provides boundary files for states, counties, and cities.
2. Commercial vendors: Companies such as TomTom, HERE, and TeleAtlas provide vector data for a fee. These data sets are commonly used in navigation and mapping applications.
3. Open data portals: Many cities and states provide open data portals where vector data can be downloaded for free. For example, the city of San Francisco provides various GIS data layers, such as land use, zoning, and street centerlines.

Understanding Raster GIS Data

Raster data is a type of GIS data that represents the earth’s surface as a grid of pixels. It is commonly used to represent continuous features such as elevation, land use, and temperature. Raster data is stored as a matrix of cells, each with a specific value representing a feature such as temperature or elevation.

Raster data is often used to create maps that show the distribution of different features across a landscape. For example, a raster map of temperature can be used to identify areas that are warmer or cooler than other areas. Raster data falls under two categories: continues and discrete.

Continuous rasters describe cells on a grid that gradually change – for example, elevation, sea level, or temperate.

Discrete rasters are assigned to specific theme or class with well-defined boundaries. Things like tree locations, rivers, and roads would all fall into discrete datasets.

The advantage of raster data is its ability to handle large data sets and its suitability for analyzing continuous data. However, the disadvantage is that it is not suitable for representing complex shapes or overlaying data sets.

Raster data can be obtained from various sources, including:

1. Government agencies: Many governments provide free access to raster data on their websites. For example, the US Geological Survey provides various raster data sets, such as digital elevation models and satellite imagery.
2. Commercial vendors: Companies such as DigitalGlobe and Airbus provide raster data for a fee. These data sets are commonly used in remote sensing and earth observation applications.
3. Open data portals: Many organizations provide open data portals where raster data can be downloaded for free. For example, the European Space Agency’s Sentinel Hub provides access to satellite imagery data sets.

Converting Other GIS Data Types

Often, you will come across data that needs to be converted into different formats. This is a necessary task as different software and applications may require different file types. Here are the commonly used GIS types that often need to be converted to other formats:

1. Shapefile – A shapefile is a commonly used GIS file format that contains both spatial and non-spatial data. It is compatible with most GIS software and can be converted into other formats using the Export function in ArcGIS or the Save As function in QGIS.
2. KML – KML is a file format used in Google Earth and other mapping applications. To convert a shapefile to KML, you can use the ArcGIS tool called “Layer to KML” or the QGIS tool called “Save As” and choose the KML format.
3. GeoJSON – GeoJSON is a file format that is commonly used on the web for sharing geospatial data. To convert a shapefile to GeoJSON, you can use the “Export to GeoJSON” tool in ArcGIS or the “Save As” function in QGIS and select the GeoJSON format.
4. CSV – A CSV file is a comma-separated values file that is commonly used for storing tabular data. To convert a shapefile to CSV, you can use the “Table to Excel” tool in ArcGIS or the “Export” function in QGIS and select the CSV format.

In summary, GIS data obtained from various sources can be categorized into two types: vector and raster data. Vector data is commonly used to describe objects with a well-defined boundary, while raster data is used to describe continuous data. GIS professionals must understand these data types and their sources to effectively use GIS in their work. Additionally, it is important to note that GIS data can come in different formats, such as shapefiles, geoJSON, and KML, and may require preprocessing before analysis.

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