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2,784 post(s)
#06-Aug-17 21:13

As far as I can tell, functions on images seem to be mostly confined to working with a single image. It seems like Manifold took the approach to go after the embarrassingly parallel solutions first, and will later move to integrate images with vector information.

I have a large satellite land cover file for a State, and I want to find those areas that are agricultural (a particular classification in the raster). I'd like to know how many of these pixels (the agricultural ones) are in each soil area (drawing).

I could do this in 8 with some SQL, and there were even functions that would allow us to find a pixel that was inside an area. Am I correct in assuming that Radian currently doesn't have the ability to do this? If it does, what transform or SQL function allows it?


7,031 post(s)
#07-Aug-17 06:09

You can always split tiles into pixels, convert each pixel into a point geom and drop point geoms onto areas, but a built-in function would work much faster, and built-in functions for that are not yet integrated (but will be, this is in the plans).


7,283 post(s)
#07-Aug-17 15:48

In the meantime, is it a good strategy to first drop tiles (as bounds) onto area hulls as a prefilter, split only required tiles, then drop pixels as points (better: bounds again) onto areas?

What strategy will built-in functions use? (Hints.)


7,031 post(s)
#08-Aug-17 06:44

What strategy will built-in functions use?

In this particular case, we will project vector to raster instead of raster to vector.

lionel82 post(s)
#13-Aug-17 05:03

1) built in function mean SQL or function that can be call from programming language ( python vbscript) ?

2) Can SQL work both on raster and Drawing for input parameters ?

3) "We will project " mean do all the work on raster so convert any vector data to raster data ?

4) Radian let us create many drawings from the same table so Drawing is only a view of data and SQL work only on table not on drawing ? !! So why use Drawing name in SQL rather than Table Name ?

5)Same for image : each time we create an image we create also a table !!! but table of drawing and image doesn't contain the same fields !!! So i try to create a drawing base on table of raster but do it like this seem not available !!



7,031 post(s)
#13-Aug-17 06:49

1 - SQL. Any SQL function can be called from a script (and the reverse is true as well sans custom types).

2 - Queries can work on tables with tiles and on tables with geoms, yes.

3 - By "we will project vector to raster" I meant that in this specific case of computing the number of pixels (of specified type) under a vector object, our function will likely project the vector object to the pixels and perform the counting in the pixel coordinates and not the other way around.

4/5 - A table can have multiple drawings built on it, but a drawing is only built on a single table. The query engine allows using the name of the drawing as a shortcut for the name of the table that the drawing is built on, this is unambiguous. Same for images.

Hope this helps.

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