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Category: Spatial

Geospatial Data Processing with Databricks

Razavi and Michael Johns walk us through examples of processing geospatial data with Databricks:

Earlier, we loaded our base data into a DataFrame. Now we need to turn the latitude/longitude attributes into point geometries. To accomplish this, we will use UDFs to perform operations on DataFrames in a distributed fashion. Please refer to the provided notebooks at the end of the blog for details on adding these frameworks to a cluster and the initialization calls to register UDFs and UDTs. For starters, we have added GeoMesa to our cluster, a framework especially adept at handling vector data. For ingestion, we are mainly leveraging its integration of JTS with Spark SQL which allows us to easily convert to and use registered JTS geometry classes. We will be using the function st_makePoint that given a latitude and longitude create a Point geometry object. Since the function is a UDF, we can apply it to columns directly.

Looks like they have some pretty good functionality here, and they have shared the demos in notebook form.

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Drawing Spatial Lines with SQL Server

Hasan Savran takes us through spatial data types in SQL Server:

In this post, I want to show you how easy it is to draw a spatial line by using spatial points. To make the following demo to work, you must have SQL Server 2017 or later. The reason is, I will use the new system functions STRING_AGG and CONCAT_WS. There are not Spatial functions and you can draw a spatial line by using spatial points. They will make this process easy. You can read about these new function in my older post here.

     I downloaded Hurricane data from NOAA for free. Dataset has the location of the hurricane eyes in latitude and longitude. By knowing the location, its pretty easy to display these points as Spatial data (geography). I wanted to connect these points to each other and create a line, by doing that I could add a buffer around the line and make a spatial range search and find if I have any customer under this line.

I think spatial data types are probably one of the lesser-utilized data types with respect to how useful they can be.

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Using Graph + Spatial to Find Closest Points

Hasan Savran shows how you can combine graph tables with spatial data types in SQL Server to find the nearest thing—in this case, a distribution center:

Today, I want to show you how Graph Processing Tables can make your data models flexible and smart. Let’s say we work in a e-commerce company, we have many users and products just like Amazon. We also have many warehouses, same product might be located in multiple warehouses. Whenever we want to ship a product, we want to pick the closest warehouse to buyer. In this way, we should be able save good amount of money for shipping and products will arrive to our customers locations faster.

Click through for the demo.

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Handling Spatial Data in Cosmos DB

Hasan Savran gives us some tips on storing spatial data in Cosmos DB:

Importing Spatial Data into CosmosDB can be a challenge. CosmosDB is not a relational database and you may need to change your data model structure to add spatial data. You cannot create a new container for spatial data and plan to join this container to your other containers. There are free tools which might help with GeoJson conversion, but you may still need to add converted geoJson data into your data models. Spatial data becomes very powerful when you find a way to join it with your application’s data.

    In the following example, I am going to download the hurricanes from NOAA website. Data is in CSV format so we may need to transform data to create a good data model for CosmosDB. I downloaded the all hurricane data for 2005 which was the year of Katrina hurricane. First thing I did, was to change the name of columns and make them more user-friendly. I have used the following names for columns. Here is a sample row from the CSV file.

Click through for the example.

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Azure Databricks Geospatial Analysis

Jose Mendes gives us an example of using Azure Databricks to perform geospatial analysis:

Magellan is a distributed execution engine for geospatial analytics on big data. It is implemented on top of Apache Spark and deeply leverages modern database techniques like efficient data layout, code generation and query optimization in order to optimize geospatial queries (further details here).

Although people mentioned in their GitHub page that the 1.0.5 Magellan library is available for Apache Spark 2.3+ clusters, I learned through a very difficult process that the only way to make it work in Azure Databricks is if you have an Apache Spark 2.2.1 cluster with Scala 2.11. The cluster I used for this experience consisted of a Standard_DS3_v2 driver type with 14GB Memory, 4 Cores and auto scaling enabled.

In terms of datasets, I used the NYC Taxicab dataset to create the geometry points and the Magellan NYC Neighbourhoods GeoJSON dataset to extract the polygons. Both datasets were stored in a blob storage and added to Azure Databricks as a mount point.

It sounds like this is much faster than using U-SQL to perform the same task.

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nUnit Tests And Spatial Data Types

David Wilson shows how to build integration tests in nUnit when you’re using spatial data types:

I was recently working on a .NET 4.6 based project that was using EF 6 and nUnit for unit testing. While setting up some integration tests against a local SQL database I was receiving this error:

Spatial types and functions are not available for this provider because the assembly ‘Microsoft.SqlServer.Types’ version 10 or higher could not be found.

We had recently been using SQL Server spatial types for tracking geograpic locations and the tests which performed updates and inserts against these fields were failing.

Read on for the setup instructions.

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Spatial Workaround In Azure SQL Data Warehouse

Rolf Tesmer has you covered if you want to perform spatial queries against data in Azure SQL Data Warehouse:

Recently we had a requirement to perform SQL Spatial functions on data that was stored in Azure SQL DW.  Seems simple enough as spatial has been in SQL for many years, but unfortunately, SQL Spatial functions are not natively supported in Azure SQL DW (yet)!

If interested – this is the link to the Azure Feedback feature request to make this available in Azure SQL DW –

AND SO — to use spatial data in Azure SQL DW we need to look at alternative methods.  Luckily a recent new feature in Azure SQL DB  in the form of Elastic Query to Azure SQL DW now gives us the ability to perform these SQL Spatial functions on data within Azure SQL DW via a very simple method!

Check out that Azure Feedback item if you’d like to see native spatial support rather than using elastic query.  In the meantime, click through to see Rolf’s workaround.

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SQL Server And Polygons

Bert Wagner shows that SQL Server interprets polygon definitions a bit differently from GeoJSON:

Discerning eyes might notice that SQL Server didn’t shade in the area inside of the polygon — it instead shaded in everything in the world EXCEPT for the interior of our polygon.

If this is the first time you’ve encountered this behavior then you’re probably confused by this behavior — I know I was.

Read on to learn more about left-hand and right-hand polygon specifications and how to translate from one to the other.

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Spheres In SQL Server

Slava Murygin continues his quest to build a graphics engine with spatial data:

Couple of years ago I came up with an algorithm of drawing an ellipse using SQL Server spatial geometry:

I’ve used that algorithm to make a sphere and as in my previous blog of drawing 3D Cube I use external procedure to simplify the process.
This time instead of temporary stored procedure I’m using a function to generate Geometrical content.

This has been an enjoyable series so far, showing how to build different shapes using spatial queries.

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Drawing Cubes With SQL Server Spatial

Slava Murygin has entered his cubism phase:

Hey, there is a time to go level up and instead of drawing Spirals, Fractals and other cool stuff I decided to go 3D!

So, the first my try will be drawing 3D cubes.
As you know, SQL is not an Object Orienting Programming language, and I can’t just simply create an Object “Cube” with certain properties. To create a Cube I need a Stored Procedure:

Click through for a touch of Picasso in your database.

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