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Welcome to this guide on exploring geospatial data analysis with SQL and understanding the various applications of Geographic Information Systems (GIS). SQL, which stands for Structured Query Language, is a powerful tool for managing and analyzing large data sets stored in relational databases. When combined with an understanding of GIS, it is possible to conduct powerful spatial and geographic analyses directly within the database.
Understanding GeoSpatial Data
Geospatial data, or spatial data, are data points that are associated with a specific geographical location. These could be coordinates, addresses, or even just a city name. Geospatial data analysis is the collection, display, and manipulation of imagery, GPS, satellite photography and historical data, described explicitly in terms of geographic coordinates or implicitly in terms of a street address, postal code, or forest stand identifier as they are applied to geographic models.
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-- code example for selecting all data from Geospatial table SELECT * FROM Geospatial |
SQL and GIS Applications
SQL procedures enable you to perform advanced analysis and optimization on data within the database without additional coding. These analyses can yield meaningful insights that can be used across various sectors - urban planning, hazard assessments, disease tracking, population growth, and crime pattern analysis being to name a few.
Example SQL Code for GIS applications
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-- Calculate the distance between two lat-long coordinates CREATE FUNCTION CalculateDistance(@lat1 FLOAT, @lon1 FLOAT, @lat2 FLOAT, @lon2 FLOAT) RETURNS FLOAT AS BEGIN RETURN ( 3959 * acos( cos( radians(@lat1) ) * cos( radians( @lat2 ) ) * cos( radians( @lon2 ) - radians(@lon1)) + sin( radians(@lat1)) * sin( radians( @lat2 )))) END |
Using GIS in SQL
PostgreSQL, an open-source advanced SQL platform, offers PostGIS, a spatial database extender, which allows for geographic objects support. It also lets you run location queries in SQL. For example:
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-- code example for using PostGIS functions for spatial queries. SELECT building_name FROM Buildings WHERE ST_DWithin( -- Define the geospatial point from where the distance will be calculated ST_SetSRID(ST_MakePoint(-73.9935, 40.7506), 4326)::geography, -- Define the geospatial column that contains the geospatial data in your table location::geography, -- Define the maximum distance (in meters) 100 ) |
Analysing geospatial data with SQL is a powerful tool to produce data-driven decision-based solutions. By honing these skills, you’ll open doors to solving real-world problems of a diverse range.