Tag Info

New answers tagged

0

One of my new favorite tricks is string_agg(). If You can get your data into a modern database, then you have code like this SELECT STRING_AGG(a.tile, ',' ORDER BY a.tile) As tiles FROM cuy_contour_tiles AS p, cuy_contour_tiles AS a WHERE ST_Touches(p.geom, a.geom) AND p.tile = 'MyCensusTractOfInterest' GROUP BY p.tile ORDER BY p.tile; The code ...


1

Euclidean Distance and Zonal Statistics (As Table) will tell you the average distance to the closest point for each polygon. It's worth considering that Euclidean distance is not walking distance. Walking routes are restricted: a person can't (reasonably) walk over a building, an interstate highway, a river/stream, etc. A more accurate method would be to ...


1

for the average walking distance to the closest point, you can indeed use the Euclidian distance to create a raster of the distance to the closest point. Then you can compute the average distance using zonal statistics (or zonal statistics as a table if you prefer a vector output)


1

Doing this iteratively in a model with selections is one approach but there are a couple of other options that I think would eliminate the need for iterations. I'm not entirely clear if you're trying to fit a solution into a larger model you've already built or going the model route because of the size of the data and necessary iterations to use selections. ...


0

You're really most of the way there. While && or ST_Intersects will find you which block groups overlap which ZIP codes, you are returning the geometry unmodified in your SELECT list. If you want the block groups clipped to the ZIP codes, you have to use a function which actually modifies the geometry, viz. ST_Intersection. In the PostGIS Reference ...


1

in a model, you can use the "select by location" tool (management > Layers and table view). The little trick is that you first need to create a layer (with the "make feature layer" tool, same location) before you can use the "select by location" tool. based on your updates, you could also consider the use of "tabulate intersection" providing you have the ...


0

Using SQL Server, I've found luck converting the target layer to points (centroids) then selecting them: select * from polygonA, polygonB where polygonA.shape.STIntersects.STCentroid().shape(polygonB.shape) = 1) and here's the syntax I use for STWithin, which also does a great job: select * from polygonA, polygonB where ...


4

The Census Bureau has prepared so-called "Relationship Files" that describe the geographic relationships between geographies (including tracts) at different times. This includes a lot of information for going between the two datasets by population or land area (a complete list is below). In your case, since you're trying to go from 1990 to 2010, you will ...


1

The Census Bureau's "relationship files" (specifically the "Geographic Relationships Over Time (Comparability)" for Census Tracts) should be exactly what you're looking for. Download 1990-2000 and 2000-2010.


0

Apparently now you can only get Block-level 2010 population data for U.S. Territories? Anyone know why states are no longer available?


2

Try NHGIS, which allows you to get blocks for all states. Set the filters as I have done in the attached screen shot.



Top 50 recent answers are included