Thinking in GIS

GDAL is most likely the most powerfull GIS toolset out there, with very geekish features that may seem complicated at first, but become extremely powerful and simple at the same time once you master them. One of these features I most like is the virtual format concept, valid both for raster data sources (GDAL) and for vectorial data sources (OGR).Basically GDAL gives to the user a very simple mechanism to create virtual formats from some different sources.Let's analyze this feature, with a couple of samples derived from real world scenarios I have been envolved in the last weeks.GDAL gives the...
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There is a recurring question at GIS mailing lists, forum and at some extent in my mailbox: what is the best way to master Python for developing geospatial applications?I myself had this question far away in 2006 when I started switching from proprietarysoftware to Open Source, and had identified in Python the way to go.In this post I will try to quickly summarize what is the best way to go in my opinion.If you are completely new to Python, first things to check out, are some very basic and popular resources, like these ones:the official Python tutorialthe "Dive into Python...
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Today in the GDAL mailing list Frank Warmerdam has announced that GDAL 1.9.0 has finally been released.Being a major new release, it offers many new features, but what I was waiting for is the support for Esri File GDB and Google Fusion Table.So I couldn't resist to install it and giving a try.For using the File Geodatabase driver I had to dowload the Esri File Geodatabase API (you need to be registered for downloading it).It was then just a matter of setting the value of the library path in the LD_LIBRARY_PATH variable, and using the --with-fgdb GDAL configuration option when...
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Today together with Paolo Cavallini, I have been trying to figure out a workflow for managing documentation's translations for QGIS.There are many tools for managing documentation workflows out there: a common approach to which I have been exposed by following both the Python and the OSGeo communities is to keep the documentation source files in the reStructured Text markup format, and to generate the end user documentation with tools like docutils and Sphinx to a bunch of different formats (i.e. html, odt, pdf, latex... just to name a few).Python documentation itself and two wide spread GIS projects like MapServer and...
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PostGIS in action has landed: finally a book about PostGIS, we were all missing it!A software project that has a public visibility since almost 10 years, with a large community and a long series of use cases, finally has its deserved book.I started using PostGIS in 2006 in a situation where the company I were working for at that time had to cut the cost of licenses and maintenance. Opting for FOSS gave us also the possibility to eliminate long administrative times needed to change any of the requirements in the licenses.But above all, we knew to select a technology...
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If you have ever tried to interact with a WFS (via a browser, or curl, or OpenLayers or whatever), you are fully aware that it has alway been a pain to interact with, and until now the only Python library that made life simpler was the excellent OWSlib by Sean Gillies (that, BTW, will deserve itself another post at this blog in the next weeks).But since some weeks, from the release of the GDAL version 1.8.0, a new toolset is available to GIS users and developers via the new included GDAL WFS Driver (that will now make good company to...
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These are my quick notes for installing Oracle Instant Client on a Linux box (currently I have tested this on a Ubuntu 10.10 64 bit box and with Oracle 11.2 and GDAL 1.8.0), and then configuring GDAL for using Oracle (OCI and GeoRaster drivers support).Finally I will show how to configure GeoDjango to use an Oracle spatial database by using the Cx_Oracle Python library.First download Oracle Client files from here or here if you are on a 64 bit architecture.You need to download the following 3 zip archives:~/software/oracle$ lsinstantclient-basic-linux-x86-64-11.2.0.2.0.zip instantclient-sdk-linux-x86-64-11.2.0.2.0.zip instantclient-sqlplus-linux-x86-64-11.2.0.2.0.zipThen extract the archives to a location...
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So, after five years of blogging I have sent my Wordpress blog to pension and I have moved my blog to Blogofile.You may wonder why I have moved my blog from a spread and fully featured platform to an almost unknown exotic one.Basically I wanted to have the following advantages:Python framework, with the possibility to write in this language plugins and extensionsability to write my blog posts offline, in a markup format like REST or Markdown, with viblog system able to generate static content from the posts written in the markup language, in a Sphinx fashion, without the overhead of...
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Last week I have been attending the GFOSS Day 2010 in Foligno, basically the FOSS4G Italian Event that is held every year.The conference was split in two days: in the first days a good number of workshop and tutorials were given, related to a number of geospatial technologies.In the second day there were the instutional talks, mostly related on the open data theme.This year I myself gave two talks at the conference: in the first day, togheter with Alessandro Pasotti, we have been giving an extended tutorial about developing geospatial software with Python, here are the slides:Developing Geospatial software with...
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In many situations, in your web applications, you will need a feature for geocoding an address, a city, a country...A possible approach is to use the Javascript API of the main geocoding services (Google Maps, Yahoo! Maps, GeoNames...).But as I have showed in a previous post, if you are using Python, there is an excellent API that will take care of this, without Javascript headaches: GeoPy.In this post I will show how to use geoPy, OpenLayers and a bit of JQuery to assemble a simple but nice tool for geocoding within OpenLayers.In my server code I will use Django but...
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This year I was enough lucky to have the possibility to attend at the FOSS4G World conference in Barcelona (thanks to my company for having send me there!) - that has been run just this week, as many of you may already know.I just came back home yesterday night and until my impression are still very clear, I were thinking it is a good idea to post them here.The conference, as you may know, is held every year and is organized by OSGeo. They try to organize it every year in a different continent, and this year was the time...
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In Italy, recently, a new law is being discussed and if approved it will substantially reduce the hours Geography is taught in schools.My blog, together with other Italian mayor GIS related blogs, is going to support this petition by AIIG, Associazione Italiana Insegnanti Geografia (Geographic Teachers Italian Association):SCHOOLS WITHOUT GEOGRAPHYDoing geography at school means educating citizens of Italy and the world to be aware, independent, critical and responsible, to know how to live their lives within their environment, and how to change it in a creative and sustainable way, with an eye to the future.In the new curricula...
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In the last months there has been a plenty of activity in the non relational (NoSQL) database world.NoSQL database tries to solve 3 main RDBMS problems:Scalability, for example the ability to automatically partitioning data across multiple machinesPerformance, in some case RDBMS can be very slowFixed schema: RDBMS have nice goodness (referential integrity, relationships, triggers...) but force you to store any object to a fixed schema (migrations are a pain!)Basically there are several different kinds of NoSQL database:Key/Value (Scalaris, Tokio Cabinet, Voldemort): store data in key/value pairs: very efficient for performance and higly scalable, but difficult to query and to implement...
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There are now may geocoding web services out there, like Google geocoder, Yahoo geocoder, geocoder.us (only for US address), Microsoft MapPoint, GeoNames and MediaWiki.Normally you may access this web services API directly with HTTP REST request, and get a response in common formats like , JSON, KML.For example you may geocode with the Google geocoder an address like this one: "1071 5th Avenue, New York, NY" with a request like this one:http://maps.google.com/maps/geo?q=1071+5th+Avenue,+New+York,+NY&output=json&oe=utf8&sensor=true_or_false=&key=your_apy_keyIn this case we are querying the Google geocoder web service to get a response in json via the output parameter in the query string. This is the...
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My friend Diego Guidi is the smartest GIS/.NET developer I personally know here in Italy. He is the developer of NetTopologySuite, the port in the .NET world of the popular Java's JTS Topology Suite from VIVID Solutions. I wanted, sooner or later, write some stuff here about WMS and TMS, and now I am very happy that Diego asked me to publish this brilliant article about this topic.First of all, let me thanks Paolo for hosting this post! I hope that this article can be interesting and useful like other stuff that you can find here...IntroductionThere are a lot of...
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As many of you can have already read, ArcSDE for Postgres is coming out at ArcGIS 9.3 (it is currently in the release candidate state). It will let you store geometries in two formats, Esri geometry and PostGIS geometry, in the same fashion ArcSde for Oracle is letting Esri or Oracle geometries be stored. I have seen some interest in the GIS community about this new, and i was reading interesting posts by Bill Dollins, Paul Ramsey, James Fee and Dave Bouwman, so I thought i would post here my opinion. Plus, as some of you may already know, zigGis...
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In the previous post we have seen an introduction to FeatureServer, and we were just playing with the base edit sample, with the scribble layer.Now it is time to use FeatureServer with our datasets: I am assuming that you will want to create FeatureServer services for shapefiles, PostGIS layers, OpenStreetMap, Twitter and Flickr.Data preparation for this demo1) shapefilesIf you want to follow my steps, you can download the sample shapefiles of New York I was using to assemble this demo here: select New York as a state and then as a county, and download the Block Groups and the Roads,...
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...well, this is the solution to your problems (at least I hope so).I am continuing receiving emails from people in despair that cannot successfully use this tutorial. I am sorry but I cannot answer to all this emails, so I thought to write this post in order to allow people to configure it correctly.BTW, this demo is still working since 2 years without any problems, and the code there is just the same you can download from this blog. So it must work also for you ;-)So if you just cannot use it, this is a check list:If you receive...
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Some friends already spoke me well about FeatureServer by Metacarta in the last weeks, so I already was waiting for having a bit of time to get started with it. Then James posted this on his blog, and my curiosity was definitely fired.So I decided to spend a day for installing and testing it, without thinking of the lack of documentation (FeatureServer is still a young project, so no wonder here if the only way to get infos is digging in the source code and posting to the mailing list). The day I considered to spend on it then spawned...
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With this post I will show how to install PostGIS 1.2.1 on Postgres 8.2.5 in Ubuntu 7.10 (but this procedure should work also for previous PostGIS/Postgres/Ubuntu versions) from repositories.I will also show you how to load and secure GIS data and how to access them with some cool OS GIS Client (QGIS, UDig and gvSIG).If you use this instructions together with my previous post, you will have a fully functional GIS Server Open Source Ubuntu workstation!-1- Install PostgresIf you haven't Postgres, you need to install it (PostGIS runs on top of it). Open an Ubuntu terminal, and type:sudo apt-get install...
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With this post I will show hot to install MapServer 4.10.3 in Ubuntu 7.10 (but this procedure should work also for previous Ubuntu versions) from repositories.1) set Ubuntu sources needed for this softwareAdd universe ( http://archive.Ubuntu.com/gutsy/universe ) and multiverse repositories to your sources (by default are not in Ubuntu)sudo gedit /etc/apt/sources.listand uncomment this two lines:deb http://archive.ubuntu.com/ubuntu/ gutsy-security main restricted universe multiversedeb-src http://archive.ubuntu.com/ubuntu/ gutsy-security main restricted universe multiversesave the sources.list file and then then update your sources:sudo apt-get update2) Install MapServernow download and install MapServer:sudo apt-get install cgi-mapserver mapserver-bin mapserver-doc php5-mapscript python-mapscriptMapServer 4.10.3 will be installed (latest of MapServer 4.x serie,...
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zigGIS 1.2, the Open Source ArcGIS Desktop's connector to PostGIS, has just been released and you can download it here.This is a major release, as far it implements new important features like selections and rendering. At this time editing is still not supported (so it is still a read only connector).Also ArcMap documents persistence is now fully supported, meaning that you can save your mxd document with your PostGIS layer in them, and then open them again without problems.zigGIS should correctly work with ArcGis 9.0 (sp3), 9.1 and 9.2. Before installing it don't forget to install .NET support for ArcGis.Here...
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In my previous post I have showed you how to install and using zigGIS for adding PostGIS data into ArcMap.From the ArcMap user interface you just need to press the zigGIS button and an "Add PostGIS data" dialog will be shown to you. From there you can set a zig File path, where PostGIS connections settings are stored, and then a PostGIS layers list will be shown and you can check which layer(s) add to the map.In this post I will show how to programmatically use zigGIS and ArcObjects to add PostGIS data into ArcMap.zigGIS is a Microsoft .NET 2.0...
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zigGIS is an Open Source PostGIS connector for ArcGIS Desktop, that enables ArcMap to add PostGIS layers in the map.Differently from other kinds of connectors, like for example PgArc, the very nice feature of zigGIS is the direct-read of PostGIS data, without the needs of proxy shapefiles. This meaning that the PostGIS features are directly readed and displayed in ArcMap from the PostGIS data source without a previous conversion to a Shapefile or personal GDB.This is a very interesting project, but still in a very early phase, in fact there are still important issues that are planned to be solved...
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I wanted to leave a comment in this Bill Dollin's post, but after that it came out to my mind to leave a trackback to it, and going with a my own post on this subject as far as I have several things to discuss about.In the OSS jungle, it looks there are in the last times more and more solutions and projects based on commercial closed-code software. For example zigGIS, the Open Source ArcGIS connector for PostGIS, in which I am involved, is by itself an OS project tied to proprietary frameworks (Microsoft and Esri). This is many times...
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