SQLite \ .Net Topology Suite \ Distance() units?

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
25/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
csharp, sqlite
Domain
database

Research direction

Start by comparing EF Core 5.0.1's SQLite spatial translation for Distance() with the SQL Server STDistance() translation and the Spatialite distance functions described in the issue. Reproduce the WGS-84 three-point example using the two SQL queries shown; done means determining and implementing the correct meter-based behavior, with provider tests covering the result.

Written by the indexing model from the issue text.

Description

area-spatial customer-reported needs-design priority-bug

Is it possible to match up the functionality between SQLite and SQL Server regarding the spatial distance function?

WGS-84 Coord System, added 3 points: (1,1), (1, 2), (2, 2).

SQL Server
Calculating distances from first point - EF Core translates into spatial query using proper function STDistance()
Results are in meters, and are correct.

Sqlite
Calculating distances from first point - EF Core translates into spatial query to not the proper function.
See http://www.gaia-gis.it/gaia-sins/spatialite-sql-4.2.0.html SQL functions for distance relationships
It calls the first, which returns in angles.

There is a function underneath, that returns in meters.

I can replicate it directly in SQL browser by typing two different queries:
SELECT Distance(XXX, (SELECT YYY FROM XXX LIMIT 1)) FROM XXX;
and
SELECT Distance(XXX, (SELECT YYY FROM XXX LIMIT 1), 1) FROM XXX;

Include provider and version information

EF Core version: 5.0.1
Database provider: Microsoft.EntityFrameworkCore.Sqlite
Target framework: net5.0
Operating system: Version 16.9.6

Dominant language
C#
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