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0

You can use the function ST_DumpAsPolygons: SELECT (ST_DumpAsPolygons(rast)).* FROM road_linestring_table,dem WHERE ST_Intersects(rast, geom); Afterwards you can rasterize the result.


3

I would suggest two approaches: 1. You use Network Analyst to build a network dataset (ND) from your raw street feature class. Choosing the "Any Vertex" connectivity would create a junction point feature at each street intersection which you can export and use just like any other point feature class in ArcGIS. Start with this tutorial, the best getting ...


1

Just in case anyone has come here for a problem like this one here are a few notes: • epsg: 3577 (as Steven Kay used) is the correct spatial reference in this case (Australia) because it preserves area. Spatial references that don’t exactly preserve area (like epsg:4283) will return a slightly wrong area. Everything will need to be re-projected to the ...


1

This solution uses python (w/ arcpy) to pair up the geometry of the blocks and buffers based on their FID, performs an intersection of those pairs, and writes the resultant geometry to a shapefile along with the source features' FID. The last function within the script adds the percentage of each buffer that is made up of its corresponding 'intersection' ...


0

I am not sure if you are using ArcGIS but if you are, you can: Join the buffers with the blocks, and choose keep matching records only, step 1 gives you only the buffers that have matching fid's with the blocks then you can intersect the new buffers with the blocks. Depending on the error you get when you try to intersect the layers, it might be your ...


1

If you've got a polygon you want to use as a declared variable and intersect it with a table containing existing geometry, your query (including your polygon variable declaration) would look something like this: (MSSQL Server syntax) declare @polygon geometry = 'POLYGON((-9486683.581 4810152.256, -9282073.762 4821688.121, -9262037.786 4625578.413, ...


3

Well, the absolute difference in planning times is fractions of a millisecond. The native PostgreSQL planner has an advantage because it doesn't actually do anything for a selectivity calculation, it just returns a constant value. The PostGIS selectivity function actually figures out the selectivity, using a test against a spatial histogram of the data. This ...


3

There is no real difference other than the class of the returned object. The raster intersect function is a helper function that, for polygons, calls gIntersection from rgeos (not rgdal). I would recommend using raster's intersect functions because it will save you some steps in getting back to a SpatialPolygonsDataFrame object. One good way to explore these ...


1

from my understanding of your question, and looking at the data, you want to assign a population to each polygon. In pseudocode, something like for each polygon popn <- 0 for each intersection(polygon,pixel outline) fraction <- calculate area of intersection (as percentage of pixel outline value) popn <- popn + ...


1

In the Snapping options dialog, change the Snapping mode option to "Advanced". My Osgeo4W version of QGIS has a slight bug where if "Advanced" is already selected, you must change it to any other option and then switch it back.


0

I guess you just need to turn Snapping mode to Advanced with the dropdown box.


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You need a ST_GeomFromGeoJSON select * from points p where ST_Within( p.geom, ST_GeomFromGeoJSON('{"type":"Polygon","coordinates":[...]}') ) Edit: ST_Intersects works also (need to set SRID on GeoJSON, and transform): select row_to_json(t) from (select * from table where st_intersects( st_transform( st_setsrid( ...


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circle1 with r=107.5 naut.mile and circle2 with r=145 naut.mile intersect at points as shown in the image: One should adopt projected (Cartesian) coordinate system for this type of work. I have worked on UTM-Zone 15 because both circle center lie in this zone. If u try to do this manually/mathematically using polar coordinate system, it will be much ...



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