I’ve long delayed the configuration of GeoWebCache (GWC). Automatic configuration within GeoServer’s deployment of it has been adequate until now. Until now that I want to deploy tiles in something other than Google Mercator… . I’ve developed a cache setup for Ohio State Plane North, Feet (epsg:3734). At first it was a going to be a cache just for our service area, then I thought … Continue reading GeoWebCache Configuration
If we want to understand the factors affecting the quality of an ecological resource, adjacency is important. Adjacent land use and the fossil fuel inputs relative to keeping a land use in its current use seem to have strong correlation with, e.g. wetland quality. I’ll have a deeper post on this with some citations, but this relatively simple process of analysis is called Landscape Development … Continue reading Multi-Ring Buffers in PostGIS– Prep for Landuse Analysis
This post will be a conceptual one, rather than technology specific. Imagine a scenario where you want to provide a curated trail experience from a mobile device. You want people to be able to go to a park, pick a starting location (such as their current location) in their device, and query the system for all the possible 1-3 mile loops from that location. How … Continue reading Looping Trails– alternate routing for recreational use
Not sure this is standard SQL, but something I wanted to do is be able to cast new columns as a defined type while creating them on the fly with a SELECT statement. In this way, I might, for example, UNION or UNION ALL two dissimilar tables on the fly with a VIEW. In PostgreSQL this can be done easily, e.g.: SELECT 1::smallint as gid, … Continue reading SQL nube discovery
Naively structured data is my bane– the desire (and need) to get stuff done so often overtakes the time needed to do things the better way. So, we bootstrap. A long time ago, we managed to load in a few tens of gigs of contour data into PostGIS, partitioned it into 2ft, 10ft, 20ft, 50ft, 100ft and 250ft tables using select queries with a modulus … Continue reading Contours– Structuring PostGIS data for viewing with GeoServer
See other post for explanation: <?xml version=”1.0″ encoding=”ISO-8859-1″?> <StyledLayerDescriptor version=”1.0.0″ xmlns=”http://www.opengis.net/sld” xmlns:ogc=”http://www.opengis.net/ogc” xmlns:xlink=”http://www.w3.org/1999/xlink” xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance” xsi:schemaLocation=”http://www.opengis.net/sld http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd”> <NamedLayer> <Name>contours</Name> <UserStyle> <Title>contours</Title> <Abstract>Contour lines with index</Abstract> <FeatureTypeStyle> <Rule> <Name>rule01</Name> <Title>2 ft contours</Title> <Abstract>Abstract</Abstract> <ogc:Filter> <ogc:PropertyIsEqualTo> <ogc:PropertyName>div_10</ogc:PropertyName> <ogc:Literal>1</ogc:Literal> </ogc:PropertyIsEqualTo> </ogc:Filter> <MinScaleDenominator>1</MinScaleDenominator> <MaxScaleDenominator>4799</MaxScaleDenominator> <LineSymbolizer> <Stroke> <CssParameter name=”stroke”> <ogc:Literal>#ffd700</ogc:Literal> </CssParameter> <CssParameter name=”stroke-linecap”> <ogc:Literal>butt</ogc:Literal> </CssParameter> <CssParameter name=”stroke-linejoin”> <ogc:Literal>miter</ogc:Literal> </CssParameter> <CssParameter name=”stroke-width”> <ogc:Literal>1</ogc:Literal> </CssParameter> </Stroke> </LineSymbolizer> </Rule> <Rule> <Name>rule02</Name> <Title>10 ft contours … Continue reading SLD for contour data
A while back, I had the idea of creating a hash of geometry in order to create a unique constraint on geometry to avoid duplicate geometries in a PostGIS table. It works. It’s slow, but it works. I haven’t used it since. What I really wanted to do though was be able to detect if geometries were similar as well (not just detect identical geometries), … Continue reading PostgreSQL and Fuzzy Hashes– a natural combo?
In an earlier post, I was frustrated with the intersection of a polygon and line datasets coming out as a geometry collection instead of a simple line dataset as expected. Nicklas Avén was kind enough to point out that this is a natural consequence of the logic of an intersection, the definition of ST_Intersects is: Returns TRUE if the Geometries/Geography “spatially intersect” – (share any … Continue reading The PostGIS learning Curve: ST_Within and ST_Crosses
Just a plug for Civic Commons, a network dedicated to: “Let’s Save the Public Millions of Dollars “Government entities at all levels face substantial and similar IT challenges, but today, each must take them on independently. Why can’t they share their technology, eliminating redundancy, fostering innovation, and cutting costs? We think they can. Civic Commons helps government agencies work together. ” I haven’t used Civic … Continue reading Civic Commons
One thing I’ve learned in the last few years is that there is no theoretical reason why (properly indexed and summarized) data cannot be displayed at all scales as quickly as at any scale. This is the principle at work behind the extraordinary efficiencies of delivering data and imagery through a slippy map interface like Google, Bing, and OpenLayers as well as efficient thick client … Continue reading GeoServer and efficient delivery of raster data (image pyramid layer)
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