New answers tagged intersection
I had this problem once. <pre>NOTICE: TopologyException: found non-noded intersection between xxx, xxxx and xxx, xxx ERROR: GEOS Intersection() threw an error!</pre> I was able to resolve this error using this method. - Use QGIS - Add vector layer from your database - Take the point from the error message and search for it in ...
UK postcodes are based on the number of addresses and not area. Postcodes in rural areas are considerably larger by orders of magnitude than those in dense urban areas. In fact, large blocks of flats can even have more than one postcode at the level you mention, so you then have a problem of multiple postcodes occupying the same area, which in 2D space will ...
The only accurate way to determine the area of a postcode is to purchase the Ordnance Survey's Codepoint with polygons product. This will also give you the number of delivery points within each postcode.
Is this being done in Arc or QGIS or something? What is the desired outcome? Not sure about the vehicle you will use to represent your data, but it sounds like you want to make sure your averages are mutually exclusive to the quadrant that the data is coming from. So, the red group (ABCD) needs to only consider those pieces of data to infer the average for ...
What I want to know is the number of the red dots that are present in just one area defined by the black line. Vector | Analysis Tools | Points in Polygon will count the number of points for each polygon. Update: Since your "dots" are indeed lines - as the icon in the layer list indicates - try using Vector | Analysis Tools | Sum Line Lenght. It adds ...
You can use a Spatial Join (Analysis) to write to attributes how many times a polyline intersects a polygon feature. Consider the following sample data set comprised of polylines and polygons. From the "join_count" field, you can see polyline 1 intersects 9 polygon features, polyline 2 intersects 4 polygon features and line 3 intersects 0 times.
if you already have a field created, use 'Select by location' from the selection menu, and select all the features that intersect the other feature, then open the attribute table and use the field calculator to populate a "yes" value for the selected features.
if you also have to country boundaries in a shapefile, you could use those to clip (Vector\Geoprocessing Tools\Clip) based on the country. Or if you just want a total length value and don't need the shape itself, you could use the Analysis Tools\Sum Line Lengths tool to generate a length of each road in each country.
Assuming that OS mean Ordinance Survey then see http://www.movable-type.co.uk/scripts/latlong-gridref.html and http://www.movable-type.co.uk/scripts/latlong-convert-coords.html . Ther is exelent example howto implement conversion. Another option if you for systems that use EPSG codes 27700 and 7405 seem to be relevant ids (not necessarily correct). Target ...
X and Y are in meters (if this is the UK national grid), so compute X' = round(X + 1609.344 cos(θ)) and Y' = round(X + 1609.344 sin(θ)), for θ ∈ [−π, π], and convert the results to grid references. There's small error in this approach (X and Y differ from true distances by a scale factor which differs slightly from one).
If you run an intersection between the 2 different line feature classes, and specify the output type to be Point, then you should be able to do a count of the ids in the point table of the input lines.
You can use the Haversine formula in conjunction with basic trig to iterate a series of vertices describing your circle. Alternatively, if you have access to a GIS (e.g. ArcGIS, QGIS, PostGIS etc) or a GIS API (e.g. OGR, Shapely, GeoTools) you could simply buffer the point by one mile. E.g. for PostGIS you could use ST_Distance_sphere or ...
You're right, using ST_Intersection slows down your query noticeable. Instead of using ST_Intersection it is better to clip (ST_Clip) your raster with the polygons (your fields) and dump the result as polygons (ST_DumpAsPolygons). So every raster cell will be converted into a little polygon rectangle with distinct values. For receiving min, max or mean ...
Clip and Intersect are two similar, but different operations, but that's not your problem here. It looks to me like your Intersect worked fine, the problem is that the shape you're Intersecting with, the red frame, is a line object and not a polygon. So, the only road segments being output are the ones that directly touch that line. If you want to clip the ...
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