---------- Forwarded Message ---------- Subject: Re: [udig-devel] Topology Issues Date: Monday 11 September 2006 12:12 From: Victor Mauricio Pazos <[EMAIL PROTECTED]> To: "Vitali Diatchkov" <[EMAIL PROTECTED]>
Hi Vitali, Thank for your very very reach reply. I can see you have a maturity knowledgement. We are interested in developing Editing Features for uDig ( all our work is going to be Open Source). Now we are in inception phase then we are considered the existing solutions, and how uDig could have competitive features. We are studying many aspects: usability, design (uDig ), theory (algorithm and data structure). I agree with your approach; select features in area, SFM to TDM, edit (modify TDM) finally TDM to SFM. I would like research more about the problems that you have emphasized, especially: 1- Converting process SFM to TDM and TDM to SFM 2- Editing TDM: data strurcture, constraint checking. If we find solid arguments, we would develop some exploring prototypes and finally an open source product (maybe in GeoTools project). I think that your thesis may be a good source in this phase and I would have a look, is it possible? Thanks in advance, Mauricio On Friday 08 September 2006 16:29, you wrote: > HellO! > > Yes. I devoted lot of time to investigating Topology issues. In general, > not only in fairway of GeoTools or UDIG. Well, my MSc thesis is related > to these issues, something like "Spatial vector data processing with > topology consistency ..", that is not finished yet (long long process).. > > Here is a key issue - a data model. Most of things in GIS area are based on > Simple Feature Model while it is really simple to deal with, process, > persist, request from, etc. For operations taking into account > relationships between features such as spatial relations, topological > predicates, Simple Feature Model is not a best choice. Topology Data Model > is a solution. SFM can be converted into TDM and back. While most of the > geographical data stores are based on Simple Feature Model (because of > reasons above), there is workaround trick: at any point we need a TDM, we > can create it from SFM (not an easy issue also, btw). > > During processing of the data with taking spatial relations into account, > like features editing with topology preserving, what possible design I > see: > 1) We have a Simple Feature Model. > 2) Start edit feature with topology consistency. Here always an Area of > Interest can be defined (around feature, for example) where TDM is built > from SFM ob the fly. > 3) Real editing tools deal with TDM (with nodes, edges, faces, etc.). On > this stage it is 200% more easily to check various topological constraints > during editing, etc then if to work against SFM, also from performance > point of view. There are other advantages also. > 4) When the editing is done, TDM is converted into SFM - means all > decomposed features are gathered back from TDM entities like node, edge, > face, etc (depending on geometry type of initial SFM). > > What are weak places: > 1) There is no good and standardized implementation of TDM on Java. There > are attempts in different projects but there is no good, based on open > standard and full enough at the current moment (like JTS geometry model). > 2) The step of decomposing SFM into TDM is not that trivial, there various > optimizations are possible depending on SFM's geometry type. > 3) As a consequence there are no tools and algorithms performing over TDM. > > > What I am telling concerns open source world, proprietary implementations > exist of course (ESRI, Oracle, etc, but they are proprietary). > > > Also. It is possible to perform operations where spatial relationships are > taken into account without TDM, having and dealing only with SFM. I can > count lot of disadvantages of this approach. Actually there is a good > document by ESRI about topology data model importance and how it makes a > life easier. > > Hope it makes sense - if you wanna do the whole path - there are lot of > intermediate things to be done. The first one is an open source TDM if you > are intending to work with open source GIS. > > Best wishes, > Vitali Diatchkov. > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:udig-devel- > > [EMAIL PROTECTED] On Behalf Of Victor Mauricio Pazos > > Sent: Friday, September 08, 2006 12:56 PM > > To: User-friendly Desktop Internet GIS > > Subject: [udig-devel] Topologies Issues > > > > Hi, we are thinking to develop some issues to hand features with > > topological > > relations in uDig. > > > > issue1: Editing topological features. > > > > issue2: Process to establish spatial relationships. > > > > Someone is thinking or developing theses issues or related issues? > > > > Thanks in advance. > > > > -- > > Mauricio Pazos > > Director > > > > Axios Engineering > > www.axios.es > > e-mail: [EMAIL PROTECTED] > > tel-:+34 94 441 63 84 > > fax: +34-94 441 64 90 > > _______________________________________________ > > User-friendly Desktop Internet GIS (uDig) > > http://udig.refractions.net > > http://lists.refractions.net/mailman/listinfo/udig-devel _______________________________________________ User-friendly Desktop Internet GIS (uDig) http://udig.refractions.net http://lists.refractions.net/mailman/listinfo/udig-devel
