Tag Info

Hot answers tagged

34

You are confusing SQL and WKT (well-known text). WKT is a like a geometry language to describe shapes, but it is not SQL, which is a language to query and manipulate databases. When working with WKT in an SQL query, it must be text, and not mixed-in with the SQL. Your query works if you properly format the WKT (remove the ",") and set an SRID. For this ...


28

PostGIS based on PostgreSQL is a popular database for GIS. I haven't used it much myself, but a pro is that it's open source and that many other GIS uses it so it have an active GIS community.


25

The OSGeo is a repository for the open source GIS community. There are a few applications highlighted here that may suite your needs. Quantum GIS (QGIS) - QGIS can handle a variety of vector and raster GIS data sets. The application interface is intuitive, and has a similar look and feel like ESRI ArcMap. The application may also be installed on a ...


20

SDE [ArcSDE] can refer to at least two things: the organization of your data in the database (the SDE Schema) or a service listening for connections from clients (the SDE service). Generally they go hand in glove - the SDE service is bound to an SDE schema in a database. In its "purest" (or perhaps dirtiest) state, SDE handles all of the spatial ...


19

If your dataset is added to and updated often, then INSERT, DELETE and UPDATE statements which cause the index to be rebuilt may slow the database down. For bulk inserts, such as loading the entire OSM dataset into a database, it may be quicker to drop the indices and create them again afterwards. If it is more efficient to ignore an index (for example ...


18

I am a great PostGIS fan and have no experience with MySQL so I mght be biased. But from what you write I think of two reasons to switch. first, it will most surely be much easier to implement new features like the season map you mentioned. second, when you today do your trigonometry calculations I guess you are doing it outside the db. if you do all ...


16

If you use that id for something like as a foreign key in relation to another table your whole database will get in big trouble if you have to move a point for some reason. Probably you then will have to keep the id even if it not describes the xy-coordinates any more. As a unique key is often the best to have something not telling anything about the data, ...


16

If only because you will have a lot more choice in third-party applications for generating maps of your information (mapserver, geoserver, etc, etc) loading data (ogr2ogr, fme, etc) PostGIS would make a better choice. MySQL will only suit if your needs continue to be relatively limited.


16

See this paper (draft version): Haklay, M. (2010), How good is volunteered geographical information? A comparative study of OpenStreetMap and Ordnance Survey datasets. Environment and Planning B: Planning and Design 37(4) 682 – 703. for more rigorous assessment (in UK context). This one for assesment (in comparison wth Google Maps & Bing ...


16

GeoJSON here are the SPECs. Here's an example of a line and a polygon: { "type": "FeatureCollection", "features": [ { "type": "Feature", "geometry": {"type": "Point", "coordinates": [102.0, 0.5]}, "properties": {"prop0": "value0"} }, { "type": "Feature", "geometry": { "type": "LineString", "coordinates": [ ...


15

OSGeo4W is, well, OSGeo "for Windows", so it is not what you are looking for. I have not done it myself, but other people have, so I know it works. I would recommend you get the KyngChaos binaries for QGIS compile the OGR FileGDB driver (which will produce a "dylib" file on the Mac) drop the dylib on the plugins directory of GDAL on the Mac. I believe ...


15

Here is a Python script for ArcGIS 10 that basically does what you want, except that the output is a CSV file, not a geodatabase table. Feel free to modify and use as you like. Note that it is not well tested and not supported, so use at your own risk. """ This script looks through the specified geodatabase and reports the names of all data elements, their ...


14

Check out pgsphere, it's specifically designed for handling astronomical data. http://pgsphere.projects.postgresql.org/


14

If you don't need third party support and don't forsee the need to query by type keeping them in the same table works just fine. Alternatively you could use an inheritance model as discussed in chapter 3 of PostGIS in Action. http://www.postgis.us/chapter_03 From an architecture perspective PostGIS doesn't really care if in a query multiple different ...


14

You can use a native PostGIS database as an SDE data store. http://resources.arcgis.com/en/help/main/10.1/index.html#//002p0000006v000000 That link describes the basic setup to register a native PostGIS table with SDE. The drawback is that ESRI only supports a narrow range of Postgres and PostGIS versions, here's the list of what they support: ...


13

I feel that spatial databases should be treated no differently to traditional databases. They are essentially doing the same thing, storing large amounts of data for fast retrieval. As an example, in PostgreSQL / PostGIS, the geometry is just another datatype. Just like text, or integer. Same in SQL Server 2008. Same in Oracle. If the "spatial" part is ...


13

Several options! Within QGIS, you can "File|Save as" the shapefile directly as a spatialite database; the limitation here is that you can make a database with only one shapefile. You can use the command line spatialite_tool to load and manage shapefiles (tutorial here). It is really worth exploring the spatialite-gui and spatialite-gis standalone ...


13

Generally you can make a new geospatial table like this: SELECT * INTO europe.borders FROM wo_borders WHERE admin_lvl2 = 'eu'; -- Define a primary key ALTER TABLE europe.borders ADD PRIMARY KEY (gid); -- Spatially enable it SELECT Populate_Geometry_Columns('europe.borders'::regclass); However, by doing this you are segregating your database ...


13

While your database is technically spatial at this point, you would only be working with the inbuilt pg geometry types. In order to complete your installation, you do need to run the scripts as suggested. You can find them in your /usr/share/postgresql/[version number]/contrib/ postgis sub-directory. You should see the following: legacy_minimal.sql ...


13

If you have Ubuntu 12.04, then you should have PostgreSQL 9.1, which makes things awesome for PostGIS 2.0, where you can use use the new EXTENSION framework. To spatially enable a database, use the DDL from a SQL window: CREATE EXTENSION postgis; See other details for installing PostGIS 2.0 from source for Ubuntu 12.04 here. If you are using PostGIS ...


12

I started an open source GDAL/OGR ArcGIS plugin project this weekend that gives read support to spatialite and any other OGR vector data source like Google Fusion Tables. I have it working locally reading spatialite and will cleanup and push the rest of changes this coming Friday. I hope you find it useful. Update 1: OK, got it working today. The ...


12

[Re-posting my answer from StackOverflow. Man, this is going to be annoying if we have to do this for every question from now on.] Excellent question. I think Yahoo!'s GeoPlanet can be very useful for this: they provide a pretty exhaustive list of places and the hierarchical relationships between them, and you can either download the list of names or use ...


12

The countryInfo file from http://geonames.org (http://download.geonames.org/export/dump/countryInfo.txt) has names, country codes, languages and lots of other info. It is a tab separated list so awk or any text editor will let you select just the columns you need.


12

Speed Tests There are some very speed tests of shapefiles versus database (PostGIS) for MapServer in this presentation (from 2007). In summary: For a dataset of 3 million features running requests for 30 features one after another PostGIS was faster than shapefile (although this may have since changed by a fix to reading the shapefile index) For a ...


12

Based on your requirements, you may need a GIS stack: server, database, presentation, and then the analysis tools. I'd recommend GeoServer (http://www.geoserver.org) for server, PostgreSQL with PostGIS extension for database (http://postgis.net). This combination can enable easy distributed authoring/analysis and publishing using WFS, WPS, and WMS, which ...


12

Aside from Spatialite, you might also want to consider PostGIS. Think of it as Spatialite's big brother ;-) It's just another data source for QGIS while you can connect to it using the RODBC package in R.


12

The real advantage to spatial databases (PostGIS, spatial extensions to MySQL or anything else) is that you can do spatial operations on spatial data. If you are just storing point coordinates, then you don't really gain much from spatial (just use two numerical columns). If you store combinations of point coordinates (where the customers are), and line ...


12

While the PostGIS in Action book isn't a step by step tutorial, it is a very handy guide, and I recommend it to anyone who wants to truly understand PostGIS and get beyond just the basics of PostGIS.


12

First off, the ASTER GDEM is not a "datum," it's just a digital elevation model or DEM. The values in the ASTER GDEM are represented in the EGM96 vertical datum. Second, the ASTER GDEM is a "first return" DEM that does contain above-ground structures like buildings and trees. This is cited in the GDEM report Validation of the ASTER Global Digital ...


11

take a look at http://www.bostongis.org they have great "An almost idiot guide ..." for PostGIS, Microsoft SQL Server spatial and SpatiaLite. that is really a great start. HTH Nicklas



Only top voted, non community-wiki answers of a minimum length are eligible