Archive for the ‘Surplus’ Category

Free GIS or The value of a GIS

July 31, 2006

Many free GIS have been developed and enhanced in the last years beside the commercial products. Normally they are available as OpenSource. I can hear you scream and shout: “Oh my God! No more OpenSource!”.

That a system like GRASS was developed by the US Army plays a dicisive role. You can see at first view, that it was not developed to look nice, but the functions underneeth for analyzing bitmaps are unbeatable. GRASS is successfully used for the simulation of flood and forest fire. With the sampledata you can get a good overview what you can do with this system.

For my purposes systems like Jump/OpenJump and Quantum GIS are better suitable because they are vector-based. The features of any objects are shown in listings for one or a group of objects. Both systems have a Java-based gui. They handle data in an own format or one can save a layer as an ESRI shapefile, to mentione a well-known format. Further on they can both be connected to PostGIS (this is even true for GRASS) to read and write data in special tables.The objectfeatures can than be listed in the application. The connection is established by the GIS. The layers will be displayed in the gui. Datasets can also be limited by SQL-statements, which you can use during connection-process, to filter the objects you really need out of the whole.

I will come back to the database connection later on. Connecting to an external database gives also benefit and flexibilty to the non-GIS user. This point is also true for the commercial products, which have software interfaces for different database systems, too. The user can access an datapool which is maintenanced and administrated by a central department. To do so, the user does not have to use GIS. Pure alphanumeric data can often be accessed in an easier and faster way using special reportingtools. With the PostgreSQL-extension PostGIS you can do a spatial query without using a GIS — if you only know the correct syntax. The thing about GIS is identification and showing of data which cannot be brought in this dependency by using listings and tables. Listings and tables are good use if you want to analyze alphanumeric data. But every time an object comes along with geospatial information you can only get full potential if you identify and analyze the spatial relation.

At the moment I’m working on real estate information, like land parcels, buildings and houses. I’m in charge of the GIS. Beside our SAP, which is surely first choice for housing industry when it comes to interests based on the needs of tenants and buildings, the GIS is of real great use. Nearly 95% of information in this buisiness is geospatial referenced, so all of these information can be viewed in the application related to a single object. Based on information about land parcels, buildings and maps more information dealing with special contracts, debits and special features can be displayed at their correct location. The user can see at once what to consider about the objects. A topic which has gotten weight over the last years — in germany — is the correct billing of e. g. cutting grass and trees in the additional expense for the tenant. That means billing of all the work, that is done in the backyard and in front of the house with the plants, grass and bushes, done by an external company and not the real estate company itselfe.

All this information are — as soon as they are entered into the GIS — available in the system and can be part of a report. Additional expenses could not be prooved by the companies for years. Now the GIS knows areas and lenghts precisely. These data can be processed in internal or external applications to get the amount of expenses for a whole town or just for a single tenant.

By connecting to an external database the user can collect some information in GIS and extend it by non-GIS information that are also in this database. This is the only way to create a qualified report for objects that have a spatial dependency. As long as our data is located in one street, we can handle their dependency with a normal database. But a GIS gives you more flexibility for reports that apply to an area which you cannot describe with alphanumerical information. Economic units, quarters, colonies or related information can be added to the baseinformation of an object without problems. But to get them you have to look at a map and if you try to get a subset of it or a spanning amount they may be incapable.

I stop my post at this point and will go on with some more details and examples on single topics of the things written above.

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